77 T_h e large intestine ANATOMY OF THE LARGE INTESTINE ANATOMY OF THE LARGE INTESTINE The large intestine begins at the ileocaecal valve and extends to the anus. It is divided into the caecum, ascending colon, hepatic flexure, transverse colon with attached greater omen tum, splenic flexure, descending colon, sigmoid colon and rectum. The large intestine is approximately 1.5 /uni00A0 m long, but it can be concertinaed over an endoscope so the caecum can be reached with 70–90 /uni00A0 cm of a colonoscope. The external appearance of the colon is distinguished from the small bowel by the presence of taenia coli, three bands of longitudinal muscle that run from the appendix base to the rectosigmoid junction and fat-filled peritoneal tags known as appendices epiploicae found principally on the left side of the colon. The taenia coli act to pull the colon into its sacculated sta te, producing a series of haustrations that may be visible on abdominal radiograph and allowing distinction from distended small intestine, which has complete transverse markings caused by the valvulae conniventes (see Chapter 74 ). The important posterior relations of the caecum and ascending colon are the right ureter, right gonadal vessels and duodenum and these must be protected at surgery . The left ureter, left gonadal ves sels and tail of the pancreas must be protected when operating on the left colon. The blood supply of the large intestine from the caecum to the distal transverse colon is derived from branches of the superior mesenteric artery and from the inferior mesenteric artery and its branches more distally . The middle colic artery is a prominent branch of the superior mesenteric arter y arising soon after the origin, which divides almost immediately into Valvulae conniventes describes a fold of mucous membrane that passes across two-thirds of the bowel circumference. Sir David Drummond , 1852–1932, born Dublin, Ireland, pathologist and physician at the Royal Victoria Infirmary , Newcastle (1878–1920), President of the British Medical Association (1921–1922) and vice chancellor of Durham University (1920–1922). two or three large arcades to supply the transverse colon. The precise vascular anatomy is variable and needs to be taken into account when performing colectomy , particularly total meso - colic excision for cancer (see Chapter 65 ). Peripheral branches of the superior and inferior mesenteric vessels usually anasto - - mose, resulting in a continuous vascular supply along the colon, referred to as the marginal artery of Drummond. This vessel is often the key b lood supply to the vascular arcades, ensuring adequate perfusion of a colonic anastomosis; however, blood flow in the ‘watershed’ area of the splenic flexure representing the junction of the embryological mid- and hindgut may be tenuous. Sudden occlusion of the inferior mesenteric artery may leave the area of the splenic flexure poorly perfused, lead - ing to an ischaemic colitis. V enous and lymphatic drainage of the colon follows the arterial supply and venous drainage is into the portal system. High ligation of the artery supplying a segment of colon will therefor e also remove the lymphatic vessels and nodes, a key technical point in cancer surgery . The nerve supply to the large intestine is derived from the splanch - nic nerves via sympathetic plexuses surrounding the superior (midgut) and inferior (hindgut) mesenteric arteries. Visceral pain from the part of the colon supplied by the superior mes - - enteric arter y is thus felt, like that of the small intestine, in the periumbilical region, while pain from the colon distal to that point is felt suprapubically . The importance of non-surgical management of large • The principles of colonic surgery • That complex intestinal problems are best managed by a • The management of acute surgical problems of the large • Aetiology Aetiology Epidemiological studies suggest that diverticular disease is a consequence of a refined Western diet, deficient in dietary fibre. The combination of altered collagen structure with ageing, disordered motility and increased intraluminal pres sure, most notably in the narrow sigmoid colon, results in herniation of mucosa through the circular muscle at the points where blood vessels penetrate the bowel wall. The rectum has a complete muscular coat and a wider lumen and is thus v rarely a ff ected. Diverticular disease is rare in Africa and Asia, where the diet is high in natural fibre (Burkitt). COLITIS COLITIS There are two types of colitides: IBD (discussed in Chapter 75 ) and non-IBD. The non-IBD causes can be grouped into infec - tive and non-infective causes, with infective being by far the - most common. The majority of non-IBD colitides present acutely with severity ranging from a self-limiting illness to severe disease necessitating emergency colectomy . A careful history of acute onset and potential predisposing factors, including the use of antibiotics, is often key . Investiga - - tions include stool culture, serology and inflammatory mark - ers. Supine abdominal radiographs may demonstrate bowel oedema, colonic distension or, in severe cases, gas in the bowel wall. CT may determine the extent of disease , presence of - alternative pathology or resultant complications. In a deterio - rating patient awaiting cultures, endoscopic biopsies may also be helpful. COLOSTOMIES COLOSTOMIES A colostomy is a planned opening made in the colon to divert faeces and flatus through the abdominal wall, where they can be collected in an external appliance. Ileostomies are discussed in Chapter 74 . Depending on the purpose for which the diversion has been necessary , a stoma may be temporary or permanent. Indications for stomas are shown in Summary box 77.14 . In elective surgery stoma counselling and siting should be performed by a trained stoma nurse. The patient should be examined lying, standing and sitting to determine the optimum site, which should be away from scars, skin creases and bony prominences. In obese patients the stoma should be sited higher so that it can be easily seen. Clothing preference Frank T Paul , 1851–1941, surgeon, Liverpool, UK. Johannes von Mikulicz-Radecki , 1850–1905, Professor of Surgery , Breslau, Poland. be considered. In the emergency setting siting may be di ffi cult with a sick and immobile patient, particularly if the abdomen is distended. Summary box 77.14 Indications for colostomy formation /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF To protect a distal anastomosis or allow healing away from the faecal /f_l ow Following resection when anastomosis is unsafe or not possible To relieve obstruction when resection is not feasible To reduce disease activity (e.g. Crohn’s disease) To allow alternative bowel control (incontinence) Classification of contamination Classification of contamination The degree of infection has a major impact on outcome in acute diverticulitis. Patients with inflammatory masses have a lower mortality than those with perforation (3% versus 33%). Classification systems have been developed for complicated diverticulitis to try to rationalise the literature, the most - commonly used being the Hinchey classification ( Table 77.2 ). Haemorrhage from colonic diverticula is typically painless and profuse. Bleeding from the sigmoid will be bright red with ery y Western diseases were rare in Africa as a result of diet and TABLE 77.2 Hinchey classi /f_i cation of complicated diverticulitis. Grade I Mesenteric or pericolic abscess Grade II Pelvic abscess Grade III Purulent peritonitis Grade IV Faecal peritonitis bleeding is fortunately rare and, in fact, more commonly due to angiodysplasia, but diverticular bleeding may persist or recur, requiring transfusion and resection. The presentation of a fistula resulting from diverticular disease depends on the site. The most common colovesical fistula results in recurrent urinary tract infections and pneumaturia (flatus in the urine) or even faeces in the urine. Colovaginal fistulae are more com mon after hysterectomy . Colocutaneous fistulation is unusual in the absence of prior intervention (e.g. radiological drainage). Rarely , diverticular disease may perforate into the r etroperito neum, leading to a psoas abscess, and even fistulation to the groin. Clinical features Clinical features In mild cases, symptoms such as distension, flatulence and a sensation of heaviness in the lower abdomen may be indistinguishable from those of irritable bowel syndrome. These symptoms are thought to result from a combination of increased luminal pressure a ff ecting wall tension and increased visceral hypersensitivity . Surgical treatment is rarely , if ever, appropriate for diverticular disease in the absence of complications. - Diverticulitis typically presents as persistent lower abdom - inal pain. There may be accompanying diarrhoea or consti - pation. The lower abdomen is tender, especially over the left iliac fossa, but occasionally also on the right side if the sigmoid loop lies across the midline. The sigmoid colon may be ten - der and thickened on palpation and rectal examination may reveal a tender mass if an abscess has formed. Distinguish - ing between diverticulitis and abscess formation is di ffi cult on clinical grounds alone and radiological imaging is essential. Generalised peritonitis as a result of free perforation pr esents - in the typical manner with systemic upset and generalised ten - - derness and guarding. Clinical features Given the frailty of typical patients with sigmoid volvulus a history is not always forthcoming. Massive distension is key but pain is unusual and if present is a warning sign of isch aemia. Figure 77.16 A sigmoid volvulus. Complications of diverticular disease Complications of diverticular disease The majority of patients with diverticulosis are asymptomatic but historical studies suggest that somewhere between 10% and 30% will have symptomatic complications ( Summary box 77.11 ). Johann Friedrich Meckel (the younger), 1781–1833, Professor of Anatomy and Surgery , Halle, Germany , described the diverticulum in 1809. Denis Parsons Burkitt , 1911–1993, Irish surgeon who practised in Uganda, observed that man lifestyle. Edward John Hinchey , b. 1934, surgeon, Montreal General Hospital, Montreal, Canada. Complications of diverticular disease - /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Diverticulitis Abscess Peritonitis Intestinal obstruction Haemorrhage Fistula formation Complications of stomas Complications of stomas Stoma complications are common ( Summary box 77.16 ). The vast majority of these complications can be dealt with by a suitably experienced stoma nurse but on occasion revision surgery is needed. Stoma ischaemia is usually evident in the Figure early postoperative period and it is essential to inspect the stoma the day after surgery to assess mucosal viability . If the stoma looks ischaemic a proctoscope is useful to assess viability below the fascia. Urgent surgery is required if the mucosa below the fascia is also ischaemic. Conversely if the mucosa of the bowel immediately proximal to the stoma is viable, the patient can be managed expectantly in the hope that the non-viable mucosa will slough and the worst late result is a stenosis that can be - managed with a more local procedure. This may be preferable to an immediate, di ffi cult relaparotomy . Mucocutaneous sepa - ration can usually be managed conservatively with intensive stoma care. Prolapse is more common in loop stomas, particularly transverse colon loop stomas. If recurrent and causing prob - lems with stoma care the most e ff ective solution is re versal. Other options include conversion to an end-stoma and/or r esection of redundant bowel. Retraction is mostly a problem in obese pa tients and may require, what can sometimes be di ffi cult, revision. Minor degrees of stenosis may respond to simple dilatation with more severe or recurrent issues requiring revision surgery . Repair of parastomal hernias is particularly technically challenging and the recurrence rate is high. Simple sutured repair is associated with an almost 100% risk of recurrence and transfer to the opposite side of the abdomen, or insertion of a piece of prosthetic material within the abdominal wall ar ound the stoma may be necessary . There is some evidence that stoma trephine reinforcement with mesh at the time of ini - tial stoma formation may reduce the incidence of parastomal herniation, which may be as high as 50% over the long term. There are however complications associated with parastomal meshes including recur rence, mesh infection, fistulation and bowel obstruction. Summary box 77.16 Stoma complications /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Skin irritation Stenosis Prolapse Parastomal hernia Retraction Bleeding Ischaemia Fistulation Chakrabarti S, Peterson CY , Sriram D, Mahipal A. Early stage colon cancer: current treatment standards, evolving paradigms, and future directions. World J Gastrointest Oncol 2020; 12 (8): 808–32. Clark S. Colorectal surgery: a companion to specialist surgical practice, edn. Edinburgh: Elsevier, 2019. Crosbie EJ, Ryan NAJ, Arends MJ et al . The Manchester International Consensus Group recommendations for the management of gyne cological cancers in Lynch syndrome. Genet Med 2019; 21 : 2390– 400. Herold A, Lehur P-A, Matzel KE, O’Connell PR (eds). European manual of medicine: coloproctology , 2nd edn. New Y ork: Springer, 2017. Moran B, Cunningham C, Singh T et al. Association of Coloproctol ogy of Great Britain and Ireland (ACPGBI). Guidelines for the management of cancer of the colon, rectum and anus. Colorectal Dis 2017; 19 (Suppl 1): 18–36. recurrence after treatment for non-metastatic colorectal cancer . NICE Clin - ical Guideline 151. London: NICE, 2020. Available from https:// www .nice.org.uk/guidance/ng151. Oakland K, Chadwick G, East JE et al. Diagnosis and management 6th of acute lower gastrointestinal bleeding: guidelines from the British Society of Gastroenterology . Gut 2019; 68 : 776–89. O’Connell PR, Mado ff RD, Solomon MJ (eds). Operative surgery of the - colon, rectum and anus , 6th edn. Bacon Rota, FL: CRC Press, 2015. Rutter MD, East J, Rees CJ et al . British Society of Gastroenterology/ Association of Coloproctology of Great Britain and Ireland/Public Health England post-polypectomy and post-colorectal cancer re - section surveillance guidelines. Gut 2020; 69 : 201–23. - Seppälä TT , Latchford A, Negoi I, et al . European guidelines from the EHTG and ESCP for Lynch syndrome: an updated third edition of the Mallorca guidelines based on gene and gender. Br J Surg 2020. https://doi.org/10.1002/bjs.11902 DIVERTICULAR DISEASE DIVERTICULAR DISEASE Diverticula (hollow outpouchings) are a common structural abnormality of the gastrointestinal tract. They can be clas sified as: /uni25CF congenital : all three coats of the bowel are present in the wall of the diverticulum (e.g. Meckel’s diverticulum). /uni25CF acquired : there is no muscularis layer present in the diverticulum (e.g. sigmoid diverticular disease). Diverticula are found in the left colon in around 75% of those over 70 years of age in the Western world. The condition is overwhelmingly found in the sigmoid colon but can a ff ect the whole colon. In South East Asia right-sided diverticular dis ease is more common. Diverticula are most often asymptom atic (diverticulosis) and found incidentally , but they can present clinically with sepsis or haemorrhage. ENDOMETRIOSIS ENDOMETRIOSIS This is mainly covered in Chapter 87 . It tends to be found deep in the pelvis and therefore relates more to the rectum. On the rare occasion it is found in the colon, it may be a cause of ï¬�brosis and obstruction. Infective colitides Infective colitides Infective causes may be classified as bacterial, protozoal, viral and fungal. Common infections include the following. Escherichia coli E. coli is a Gram-negative bacillus transmitted via the faeco - oral route from contaminated food or water. Symptoms vary according to strain, with the most common form – entero - toxigenic E. coli – causing ‘traveller’s’ diarrhoea (diarrhoea, vomiting and colicky pain). In adults, infection is usually brief and self-limiting. A more severe form – enteroinvasive - E. coli – causes a more systemic illness and haematochezia. A very severe form – enterohaemorrhagic E. coli – results in colonic oedema, ulceration and haemorrhage with the very ill requiring colectomy . Campylobacter Infection with Campylobacter jejuni (a Gram-negative rod with a distinctive spiral shape) is the most common form of gastro - enteritis in resource-rich countries, typically acquired from eating infected poultry . It causes diarrhoea and abdominal pain. Severe cases may resemble ulcerative colitis. The organism supportive as it usually resolves without antibiotics, but severe colitis and even perforation may occur. Salmonellosis, typhoid and paratyphoid Salmonella are a family of Gram-negative rods that can cause a range of enteric infections. Salmonella gastroenteritis is typically caused by Salmonella enteritidis from poultry and is most often a self-limiting illness comprising headache, fever and watery diarrhoea. When severe, antibiotics, hospitalisation and intravenous fluids may be needed. The diagnosis is based on stool culture. Shigella and enteropathogenic strains of may cause similar diarrhoeal illnesses. Typhoid fever is caused by Salmonella enterica Typhi and paratyphoid fever by Salmonella enterica Paratyphi A, B or C. The clinical di ff erences between these infections are subtle. They present with fever and abdominal pain after a 10- to 20-day incubation period. Over the next week, the patient can develop distension, diarrhoea, splenomegaly and characteristic ‘rose spots’ on the abdomen caused by a vasculitis. A number of surgical complications can result: /uni25CF paralytic ileus; /uni25CF intestinal haemorrhage; /uni25CF perforation; /uni25CF cholecystitis. In addition, invasion of the systemic circulation, which is a characteristic feature of salmonellosis, can cause severe Gram-negative sepsis and septic shock may develop. Occasion ally patients develop metastatic sepsis, including septic arthri tis, osteomyelitis, meningitis, encephalitis and pancreatitis. Ye r s i n i a Yersinia , Gram-negative coccobacilli, infection results from ingestion of contaminated food, typically meat, water and dairy products. Invasion typically occurs in the ileocaecal region and may mimic Crohn’s disease. Treatment is usually supportive with antibiotics reserved for severe infection or in the immunocompromised. Shigella (bacillary dysentery) Dysentery results from the ingestion of contaminated food or water, with only a small dose of infective agent required. The Gram-negative bacilli invade the colonic epithelium, causing cell death, ulceration and necrosis. Exotoxins cause a brief period of watery diarrhoea before the onset of classical severe, bloody diarrhoea. Clostridium difficile Clostridium di ffi cile is a toxin-producing Gram-positive bacillus that is of increasing concern in many hospitals. Although normally present in around 2% of the population, it proliferates after antibiotic treatment (especially with cephalosporins). Clinically , C. di ffi cile infection presents with diarrhoea, abdominal pain and fever. Infection may progress to pseudomembranous colitis, so called because on endoscopic Burrill Bernard Crohn , 1884–1983, gastroenterologist, Mount Sinai Hospital, New Y ork, NY , USA, described regional ileitis in 1932 along with Leon Ginzburg and Gordon Oppenheimer. between oedematous mucosa are seen. Diagnosis is usually made by detection of the toxin in stool samples, rather than by culture. Treatment is by metronidaz ole or vancomycin along - side supportive care. In refractory cases, faecal transplantation to restore a healthy microbiota may be tried. If toxic dilatation occurs, an emergency subtotal colectomy and ileostomy ma y be necessary . Recently more virulent strains have stressed the importance of prevention. Suspicion of the disease should prompt source isolation, protective equipment for health sta ff , vigorous disin - E. coli fection and scrupulous hand washing. Intestinal amoebiasis Entamoeba histolytica has a worldwide distribution and is trans - mitted mainly in contaminated drinking water. It can cause colonic ulcers, described as ‘bottlenecked’ because they have considerably undermined edges. The ulcers typically also have a yellow necrotic floor, from w hich blood and pus exude. In the majority they are confined to the distal sigmoid colon and the rectum. Clinically amoebiasis can mimic ulcerative colitis, most commonly causing bloody diarrhoea. Severe colonic compli - cations can occur, including haemorrhage, stricture formation or perforation. A pericolitis is not uncommon and results in adhesions that may cause intestinal obstruction. Amoebiasis may cause liver abscesses or an amoebic mass (‘amoeboma’) of the caecum or sigmoid, whic h is di ffi cult to distinguish from a carcinoma. Surgery is fraught with danger as the bowel is - extremely friable. - Endoscopic biopsies or fresh stools are examined to look for the presence of amoebae ( Figure 77.12 ). It is important to emphasise, however, that the presence of the parasite does not indicate that it is pa thogenic. It is especially important to exclude amoebic infection in patients suspected of having ulcerative colitis. Treatment is by metronidazole in the acute phase. Diloxanide furoate is e ff ective against chronic infections associated with the passage of cysts in stools. Figure 77.12 An amoeba in a rectal biopsy (arrow). Cytomegalovirus (CMV) is present asymptomatically in 40–100% of adults. It usually remains latent within the host but can reac tivate in immunocompromised patients. Commonly a ff ected are those with acquired immunodeficiency syndrome (AIDS) (where it is the most common indication for colectomy) and patients on imm unosuppressive therapy for IBD. Symptoms include profuse bloody diarrhoea and colicky pain. Severe disease may lead to perforation. Treatment is with ganciclovir with surgery necessary for severe disease or complications. Human immunodeficiency virus Intestinal complications are common after the develop ment of AIDS when opportunistic organisms can cause gas troenteritis ( Summary box 77.9 ). Human immunodeficiency virus 1 (HIV1) may also cause a specific enteropathy . Treat ment is directed towards the responsible organism and surgery should be a voided. Summary box 77.9 Opportunistic intestinal infections in patients with AIDS /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Bacteria Viral Salmonella Cytomegalovirus Shigella Protozoa Yersinia Cryptosporidium Campylobacter Giardia Mycobacterium avium– Fungal intracellulare (MAI) Candida albicans Introduction Introduction No content extracted automatically. Investigation Investigation Radiology Plain radiographs can demonstrate a pneumoperitoneum. Spiral CT has excellent sensitivity and specificity for identify ing bowel wall thickening, abscess formation and extraluminal disease and has revolutionised the assessment of complicated diverticular disease ( Figure 77.13 ). On identification of abscesses in stable patients, drainage, under interventional radiology guidance, ma y be carried out percutaneously , avoid ing the need for laparotomy/laparoscopy . Contrast studies and endoscopy are usually avoided for 6 weeks after an acute attack for fear of causing perforation. They are used subsequently , howe ver, to exclude a coexisting carcinoma and assess the extent of diverticular disease. Contrast examination or CT can demonstrate a fistula. Colonoscopy Endoscopic assessment may demonstrate the necks of diver ticula within the bowel lumen ( Figure 77.14 ). A narrowed area of diverticular disease may be impassable because of the severity of disease and there is a significant risk of endoscopic perforation. Colonoscopy in these circumstances requires judgement and e xperience. Biopsies may be taken if possible ally contrast enema is required. Excluding a carcinoma may not always be possible and may represent an indication for resection. Figure 77.13 Computed tomography scan demonstrating an abscess associated with diverticulitis (arrow) (courtesy of Dr D Kasir, Hope Hospital, Salford, UK). Investigation A supine abdominal radiograph is useful but not always diag - nostic ( Figure 77.17 ). CT is the mainstay of diagnosis. Learning objectives Learning objectives To appreciate: The basic anatomy and physiology of the large intestine intestinal problems • The range of conditions that may affect the large intestine • To understand: The aetiology and pathology of common large intestinal multidisciplinary team • conditions The principles of investigation of large intestinal symptoms intestine • Malignant colorectal carcinoma Malignant: colorectal carcinoma Epidemiology In the UK, colorectal cancer is the second most common cause of cancer death. Approximately 42 /uni00A0 000 patients are diagnosed with colorectal cancer every year in the UK. Approximately one-third of these tumours are in the rectum and two-thirds in the colon. The burden of disease is greater in men than - in women (56% versus 44%). Colorectal cancer occurs less frequently in resource-poor than in resource-rich countries. Aetiology Most colorectal cancers are thought to develop from adeno - matous polyps through a sequence of genetic mutations influenced by environmental factors. This adenoma–carci - noma sequence is based on strong observational evidence ( Summary box 77.4 ). The adenoma–carcinoma sequence is not a simple step wise progression of mutations b ut a complicated array of multiple genetic alterations, ultimately resulting in an invasive tumour. Mutations of the APC gene occur in two-thirds of colonic adenomas and are thought to develop early in the carcinogenesis pathway . K-ras mutations result in activation of cell signalling pathways and are more common in larger lesions, suggesting that that they are later events in mutagenesis. The p53 gene is frequently mutated in carcinomas but not in adenomas and therefore thought to be a marker of invasion. A recent international consortium - has identified four consensus molecular subtypes (CMSs) of colorectal cancer based on bioinformatic analysis of gene expression in more than 4000 patients. MSI, a feature of Lynch syndrome, may occur sporadically , particularly in right- sided tumours (CMS1), while others show WNT and MYC signalling activation (CMS2), metabolic dysregulation (CMS3) and transforming growth factor beta activation (CMS4). The value of this classification in interpreting tumour aetiology , biology and targeted treatment remains to be determined. Summary box 77.4 Evidence for adenoma–carcinoma sequence /uni25CF /uni25CF /uni25CF - /uni25CF /uni25CF The distribution of adenomas is similar to that of cancers (70% left sided) Larger adenomas are more likely to be dysplastic than small adenomas The majority of early cancers have adjacent adenomatous tissue Adenomas are found in one-third of specimens resected for colorectal cancer Incidence of colorectal cancer decreases within a screening programme that involves colonoscopy and polypectomy associated with intake of red meat and particularly processed meat products (haem and N -nitroso compounds). A protective e ff ect of dietary fibre is also suggested by epidemiological stud ies. A long-held hypothesis is that increased roughage is asso ciated with reduced colonic transit times that in turn reduce exposure of the mucosa to dietary carcinogens. However, there is increasing evidence associating the colonic microbiota with inflammation, gene meth ylation and dysplastic changes. Increased risks for colorectal cancer have also been associated with smoking and alcohol. Conversely , high magnesium and calcium intake may be protective. A protective potential for antioxidants such as vitamin E and selenium is as yet unproven. The epidemiological evidence supporting prostaglandin inhibitors, particularly aspirin, in preventing colorectal cancer is substantial. Given the potential hazards of taking long-term aspirin, the challenge is to identify individuals for whom the pro tective benefits outweigh the har m. Other factors that increase the risk of developing colorectal cancer include inflammatory bowel disease (IBD) (see Chapter 75 ). Cholecystectomy may marginally incr ease the risk of right-sided colon cancer. Pathology Macroscopically , the tumour may take one of several forms: annular cancers tend to give rise to obstructive symptoms whereas ulcerating cancers tend to present with bleeding. Most large bowel cancers ( Figure 77.4 ) arise from the left colon, notably the rectum (38%), sigmoid (21%) and descending colon (4%). Cancer of the caecum (12%) and ascending colon (5%) is less common but may be gradually increasing in incidence. Cancer of the transverse colon (5.5%), flexures (2–3%) and appendix (0.5%) are relatively uncommon. Microscopically , the neoplasm is a columnar cell adenocarcinoma. Spread Colonic cancer can spread locally , via the lymphatics, bloodstream (haematogenous) or across the peritoneal cavity Friedrich Ernst Krukenberg , 1871–1946, Professor of Gynaecology , Bonn, Germany Cuthbert Esquire Dukes , 1890–1977, pathologist, St Mark’s Hospital, London, UK. The original Dukes’ classification in 1932 gave three stages, A–C. radial. Radial spread may be retroperitoneal into the ureter, duodenum and posterior abdominal wall muscles or intraper - - itoneal into adjacent organs or the anterior abdominal wall. - In general, involvement of the lymph nodes by tumour progresses from those closest to the bowel along the course of lymphatics to central nodes. However, this order ly process does not always occur. Haematogenous spread is most com - monly to the liver via the portal vein. One-third of patients will have liver metastases at the time of diagnosis and 50% will develop metastases at some point, accounting for the majority of deaths. The lung is the next most common site of metastatic disease wher eas spread to the ovaries, brain, kidney and bone is less common. Colorectal cancer can spread from the serosa of the bowel or via subperitoneal lymphatics to other structures within the peritoneal cavity , including peritoneum, ovary and - omentum. Staging colon cancer Preoperative staging is important to decide whether patients can be managed with curative intent and whether they should have neoadjuvant therapy , undergo palliative interventions including colonic stenting or have symptomatic treatment. Additional interventions include ureteric stenting, en bloc resec - tion for locally advanced disease, intraoperative chemotherapy (hyperthermic intraperitoneal chemotherapy [HIPEC]) for peritoneal disease or synchronous organ resection (e.g. liver, ov aries [Krukenberg tumour]). Information is collated, including patient characteristics (age, frailty , symptoms and comorbidities), endoscopic assessment, histological analysis of biopsies and imaging studies. These factors should be discussed in a dedicated preoperative multidisciplinary meeting. Postop - erative pathological staging should also be discussed in the same forum, allowing for decisions about adjuvant therapy . A variety of staging systems are described for colorectal cancer. Dukes’ classification was originally described for rectal tumours but has been adopted for histopa thological reporting of colon cancer. Although it is simple and widely recognised ( Summary box 77.5 ) the more detailed TNM system is r egarded as the international standard ( Summary box 77.6 ). Summary box 77.5 Dukes’ staging for colorectal cancer /uni25CF /uni25CF /uni25CF Transverse Splenic colon 5.5% /f_l exure 3% Hepatic /f_l exure 2% Ascending colon 5% Descending colon 4% Caecum 12% Sigmoid Appendix 0.5% colon 21% Rectum 38% Anus 2% Figure 77.4 Distribution of colorectal cancer by site. A: Invasion of but not breaching the muscularis propria B: Breaching the muscularis propria but not involving lymph nodes C: Lymph nodes involved Dukes himself never described a stage D, but this is often used to describe metastatic disease TNM classification for colonic cancer /uni25CF /uni25CF /uni25CF Clinical features Carcinoma of the colon typically occurs in patients over 50 years of age and is most common in the eighth decade of life. Emergency presentation occurs in 20% of cases and is associated with a considerably worse prognosis, even when matched for disease stage. A careful family history should be taken. A first-degree relative who has developed colorectal cancer before the age of 50 years may indicate one of the colorectal cancer familial syndromes. Tumours of the left side of the colon usually present with a change in bowel habit or rectal bleeding, while proximal lesions typically present with iron deficiency anaemia or a mass ( Figure 77.5 ). Patients may present with metastatic disease. Investigation of colon cancer Screening Colon cancer is suited to screening as the prognosis is better the earlier stage the disease is diagnosed and polypectomy allows the prevention of cancer development. In the UK screening is o ff ered every 2 years to men and women aged 60–74 years, followed by colonoscopy in those who test positive. Originally a guaiac-based test was used, which detects peroxidase-like activ ity of faecal haematin. Studies suggested a 15–20% reduction in colorectal cancer-specific mortality in the screened popu lation. More recently the faecal immunochemical test (FIT) has been introduced. This test is more accurate and easier to complete than the old faecal occult blood test. A one-o ff flexible sigmoidoscopy for people aged 55 was o ff er ed as a screening tool in the UK. It was shown to reduce colorectal screening. Endoscopy For symptomatic patients with rectal bleeding, direct referral from primary care for a flexible sigmoidoscopy is increasingly used. The patient is prepared with an enema and sedation is not usually necessary . The bowel can be assessed as far as the splenic flexure, allowing detection of up to 70% of cancers and almost all that cause fresh rectal bleeding. Finding left-sided colonic polyps or cancer mandates subsequent completion colonoscopy . Colonoscopy is the investigation of choice if colorectal can - cer is suspected ( Figure 77.5 ). It has the advantage of not only securing histological diagnosis of a primary cancer but also detecting synchronous polyps or carcinomas, which occur in 3–5% of cases. There is a small risk of perforation (1:1000). Radiology Double-contrast barium enema has now been largely replaced by computed tomography (CT) colonography , which is extremely sensitive in picking up polyps to a size of 6 /uni00A0 mm ( Figure 77.6 ). It has the advantage of being less invasive than colonoscopy but, if a biopsy is required, an endoscopy will still be needed. CT is used as a diagnostic tool in patients with a palpable abdominal mass. CT of the thorax, abdomen and pelvis now represents the standard means of staging colorectal cancer; patients with rectal cancer require magnetic resonance imaging (MRI) for local staging (see Chapter 79 ). Surgical treatment Preoperative preparation With the advent of perioperative enhanced recovery after surgery (ERAS) protocols, mechanical bowel preparation fell out of favour. However, there is evidence that preoperative mechanical bowel preparation in combination with pre - operative oral antibiotics not only reduces surgical site infection rates but also rates of anastomotic leak, postoperative ileus, reoperation and even mortality . Further research is required - - (note the pre /f_i x y refers to neoadjuvant radio- or chemotherapy, p refers to pathological con /f_i rmation of stage; Union for International Cancer Control, 8th edn) T Tumour stage T1 Tumour invades into submucosa T2 Tumour invades into muscularis propria T3 Tumour invades into non-peritonealised pericolic tissues or subserosa T4a Tumour breaches visceral peritoneum T4b Tumour directly invades another organ/structure N Nodal stage N0 No nodes involved N1 1–3 nodes involved (N1a, 1 regional lymph node involved; N1b, 2 or 3 regional lymph nodes involved; N1c, satellite extranodal tumour deposits) N2 4 or more nodes involved (N2a, 4–6 regional lymph nodes involved; N2b, 7 or more regional lymph nodes involved) M Metastases M0 No metastases M1 Metastases (M1a, metastasis con /f_i ned to 1 organ; M1b, metastasis to more than 1 organ; M1c, metastasis to the peritoneum) Figure 77.5 Colon cancer seen at colonoscopy (courtesy of Dr Adolfo Parra-Blanco, Nottingham University Hospitals, Nottingham, UK). but mechanical bowel preparation with oral antibiotics appears safe and could reasonably be used in combination with a surgi cal site infection bundle. This bundle should contain common and variable components such as preoperative bathing, intra venous prophylactic antibiotics given bef ore surgical incision, maintenance of normoglycaemia and normothermia and use of wound protection devices. Antithrombotic stockings should be fitted, and the patient started on prophylactic subcutaneous lo w-molecular-weight heparin. Manual compression boots may be used perioperatively . In all cases where a stoma is anticipated, careful preoperative counselling and marking of an appropriate site by an enterostomal therapist is essential. ERAS programmes are widely used to reduce the physiological insult of surgery and improve postoperative outcomes ( Summary box 77.7 ). Key elements of an ERAS programme /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Operations The operations described are designed to remove the primary tumour and its draining locoregional lymph nodes. It is unusual to find unsuspected metastases at laparotomy (or laparoscopy) after CT staging, but the presence of peritoneal metastases may predicate a palliative strategy with a segmental resection and less aggressive lymphadenectomy . Similarly , a complete preoperative colonoscopy or CT colonography will have excluded synchronous bowel lesions. The use of stapling and hand-suturing techniques for colonic anastomoses have been compared, and there is probably little di ff erence in leak rate. It is more important that healthy bowel, free of tension or distal obstruction, is used to construct an anastomosis and that patients are adequately nourished and free from active infection if anastomotic leakage is to be avoided. Carcinoma of the caecum or ascend - ing colon ( Figure 77.7 ) is treated by right hemicolectomy ( Figure 77. 8) . At open surgery the peritoneum lateral to the ascending colon is incised, and the incision is continued - - (b) Figure 77.6 Virtual colonoscopy of the right colon. (a) Computed tomography scan of the abdomen showing a caecal tumour (arrow). (b) Formatted ‘virtual’ image of the same lesion as in (a) (courtesy of Dr A Slater, John Radcliffe Hospital, Oxford, UK). Preadmission counselling Preoperative carbohydrate loading Avoidance of preoperative dehydration Avoidance of nasogastric tubes Short, transverse incisions (or laparoscopic procedure) Short-acting anaesthetic drugs Avoidance of perioperative /f_l uid/salt overload Avoidance of opiate analgesia Maintenance of perioperative temperature Prevention of postoperative nausea and vomiting Early mobilisation Early introduction of oral /f_l uids/diets/supplements Early removal of urinary catheters Continual audit of outcomes Right hemicolectomy Figure 77.7 Right hemicolectomy specimen showing an ascending colon cancer (courtesy of Dr Philip Kaye, Nottingham University Hospitals, Nottingham, UK). around the hepatic flexure. The right colon and mesentery are elevated, taking care not to injure the ureter, gonadal vessels or the duodenum. The ileocolic artery is ligated close to its origin from the superior mesenteric artery (‘high-tie’) and divided. Complete mesocolic excision with dissection along embryological planes (see Chapter 65 ) and removal of the lymphovascular supply of the resected colon with flush ligation of the ileocolic and right colic vessels at their origin from the superior mesenteric artery may improve survival in node- positive disease (Hohenburger). The mesentery of the distal 10 cm of the ileum and the mesocolon as far as the proximal third of the transverse colon is divided. The greater omentum is divided up to the point of intended division of the transverse colon. When it is clear that there is an adequate blood supply at the resection margins, the right colon is resected and an anastomosis is fashioned between the ileum and the transverse colon. If the tumour is at the hepatic flexure the resection must be extended further along the transverse colon and will involve dividing the right branch of the middle colic artery . Carcinomas of the trans verse colon and splenic flexure are most commonly treated by an extended right hemicolectomy . The mobilisation is as for a right hemicolectomy but dissection continues to include the tumour, this may include taking down the splenic flexure and excising the w hole transverse mesocolon. Some surgeons prefer to perform a left hemicolectomy for a splenic flexure cancer. This is the operation of choice for descending colon and sigmoid cancers ( Figure 77.9 ) Werner Hohenburger , contemporary , surgeon, Erlangen, Germany . left half of the colon is mobilised completely along the ‘white line’ that marks the lateral attachment of the mesocolon (see Chapter 65 ). As the sigmoid mesentery is mobilised, the left ureter and gonadal vessels must be identified and protected. The splenic flexure may be mobilised by extending the lateral dissection from below and completed by entering the lesser sac. The inferior mesenteric artery below its left colic branch, together with the related paracolic lymph nodes, is included in the resection by ligating the inferior mesenteric artery close to its origin (‘high-tie’). For full mobility the inferior mesenteric vein is also ligated and divided at the lower border of the pancreas. The bowel and mesentery can then be resected to allow a tension-free anastomosis. A temporary diverting stoma may be fashioned proximally , usually by formation of a loop ileostomy . This is usually undertaken if the anastomosis is below the peritoneal reflection of the rectum, because of the greater risk of anastomotic leakage. Laparoscopic surgery Laparoscopic surgery for colon cancer has been shown to - have equivalent overall and cancer-related outcomes to open surgery . Lymph node harvests are equivalent to open surgery and initial concerns about reports of port-site recurrence have been dispelled as world experience has grown. In the UK, the National Institute for Health and Care Excellence (NICE) has stated that laparoscopic colorectal surgery should be o ff ered to suitable patients. Operation times are longer but wound infection rates, blood loss and postoperative pain scores are lower than for open surgery . The costs of laparoscopic surgery are, however, generally higher and this may be particularly . The relevant where funds are limited. SMA MCA RCA Carcinoma ICA Figure 77.8 Schematic showing right hemicolectomy. This shows the basic plane of dissection for a complete mesocolic excision. ICA, ileocolic artery; MCA, middle colic artery; RCA, right colic artery; SMA, superior mesenteric artery. Extended right hemicolectomy Left hemicolectomy Marginal artery SMA IMA LCA Carcinoma Figure 77.9 Schematic showing left hemicolectomy. This shows the basic plane of dissection for a complete mesocolic excision. IMA, inferior mesenteric artery; LCA, left colic artery; SMA, superior mes enteric artery. If laparoscopic surgery is planned it is useful to tattoo the lesion at prior colonoscopy as it not possible to locate lesions by palpation. The laparoscopic operation has particular advan tages if performed in a medial to lateral manner, i.e. starting the dissection by controlling and dividing the major vascular pedicles and only taking the lateral peritoneal reflection once the mesocolon is completely free. Specimen retrieval and bowel anastomosis can then be perfor med via a small incision. Ded icated training in laparoscopic colorectal surgery is important as there is a relatively long learning curve. Emergency surgery In the UK, 20% of patients with colonic cancer will present as an emergency , the majority with obstruction, but occasionally with haemorrhage or perforation. If the lesion is right sided, it is usually possible to perform a right hemicolectomy and anastomosis in the usual manner. If there has been perforation with substantial contamination or if the patient is unstable, it may be advisable to bring out an ileocolostomy following resection of the lesion rather than forming an anastomosis. For a left-sided lesion the decision lies between a Hartmann’s procedure and a resection and anastomosis. An on-table washout may be necessary to remove residual faecal content in the proximally obstructed bowel. Alternatively , removal of the whole proximal bowel may be required if the colon is markedly distended or if there is concern regarding its viability . Where endoscopic and radiological facilities are present an obstructing left-sided lesion can often be treated initially with an expanding Henri Albert Antoine Hartmann , 1860–1952, Professor of Clinical Surgery in the Faculty of Medicine, University of Paris, Paris, France. obstructed bowel and may allow conversion of an emergency operation with a high chance of a stoma to a situation that can be managed semielectively b y resection and anastomosis. Although early studies cast doubt on the benefits of colorectal stenting, more recently evidence has emerged that stenting leads to a reduction in stoma rates. Postoperative care Patients should be closely monitored after colonic resection as there is a small incidence of postoperative bleeding. Anti - thrombosis measures should be continued and as currently recommended for 28 days postoperatively . There is no advan - tage to placing intra-abdominal drains after colonic surgery . Wound infections are relatively common after colonic surgery and may well be more frequent than the 10% usually quoted. Anastomotic leaks occur in 4–8% of ileocolic or colocolic anastomoses. The possibility should be borne in mind in any patient not progressing as expected or with unexplained cardiac abnormalities, fever or worsening abdominal pain. Early investigation with contrast-enhanced CT scan is appropriate. In the presence of sepsis or peritonitis, early return to theatre and taking down the leaking anastomosis with the formation of stomas is usually advised. Prolonged nasogastric drainage, intravenous fluid therapy and cautious introduction of oral fluid and diet represented traditional postoperative practice. ERAS programmes tha t include preoperative, intraoperative and postoperative com - ponents have been shown to reduce length of hospital stay from 10–14 days to as little as 3–5 days by modulating the surgical stress response and reducing postoperative ileus - ( Summary box 77.7 ). It is important to appreciate that these pr ogrammes require multiple interventions and considerable time, e ff ort and education from the surgical, anaesthetic and ward teams. Adjuvant therapy - In most patients with colon cancer preoperative chemotherapy is not required; however, a recent research study (FOxTROT) has shown that it is safe and further work on case selection has been recommended. Adjuvant chemotherapy improves survival after surgery in patients with node-positive colon cancer (stage III/Dukes’ C). Fluoropyrimidine regimes are often used, with the addition of oxaliplatin in patients who are otherwise fit and have high-risk stage III disease. Patients with stage II disease show less benefit in overall survival with adjuvant chemother - apy , thus it is reserved for those with high-risk stage II disease. Presence of MSI (in the tumour histology) also a ff ects tumour recurrence and is taken into account when making decisions with patients about chemotherap y (see Chapter 12 ). Metastatic disease Hepatic and pulmonary metastases can be resected and series have demonstrated 5-year survival of around 40% in resectable disease. CT , MRI and positron emission tomography (PET) scanning are all used to identify colorectal metastases and assess patients’ suitability for further resection ( Figure 77.11 ). Figure 77.10 Abdominal radiograph demonstrating a colonic stent in position (arrow) (courtesy of Dr D Kasir, Hope Hospital, Salford, UK). The role of chemotherapy and the timing of colonic and hepatic surgery in synchronous metastases is still a matter of debate and such cases should be carefully discussed by a multi disciplinary team. Many centres o ff er adjuvant chemotherapy as standard and neoadjuvant therapy also in those with high- risk disease. Isolated lung metastases may be suitable for resection or stereotactic radiofrequency ab lation, but they are more com monly accompanied by metastases elsewhere. In patients with widespread disease, palliative c hemotherapy is o ff ered along side symptomatic treatment and support by a palliative care team. Prognosis Overall 5-year survival for colorectal cancer is approximately 58%. While there are numerous factors that may predict prog nosis ( Summary box 77.8 ) the most important determinant is tumour stage and, in particular, lymph node status. Patients with disease confined to the bowel wall (TNM stage 1, Dukes’ stage A) will usually have cure by surgical resection alone and around 95% will have disease-free survival a t 5 years. Spread beyond the bowel wall (TNM stage 2, Dukes’ B) reduces 5-year disease-free survival to approximately 85% with surgery alone. Patients with lymph node metastases (TNM stage 3, Dukes’ C) have a 5-year disease-free survival of around 45–50% with surgery alone. Adjuvant chemotherapy based on 5-fluorouracil (5-FU) and folinic acid (leucovorin) usually in combination with oxaliplatin (FolFox) is used on an individual basis for those with stage II disease (Dukes’ stage B), although the benefit is uncertain. In those with stage III disease adjuv ant chemotherapy incr the chance of 5-year disease-free survival by approximately 20% to 67–70%. Those presenting with unresectable meta static disease at diagnosis have a 5-year survival of approxi mately 10%. In metastatic disease chemotherapy based on 5-FU and folinic acid in combination with irinotecan (FolFiri) is often used as first-line treatment. Second-line therapy may include introduction of a monoclonal antibody such as a vascular endothelial growth factor (VEGF) inhibitor (be vacizumab) or an epidermal growth factor receptor (EGFR) inhibitor in immunotherapy (pembrolizumab) has been shown to have a role in MSI tumours. Tumours exhibiting the BRAF V660E mutation (approximately 10%) have a poor prognosis but may respond to treatment with combined BRAF (encorafenib) and MAP kinase (binimetinib) inhibitors. Summary box 77.8 Histopathological factors that influence prognosis /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF - Colorectal cancer follow-up Since the advent of safe liver resection for metastases the outcome benefit of follow-up has been clearly demonstrated. - Follow-up aims to identify synchronous bowel tumours (present in 3%) that were not identified at the time of original diagnosis. - Similarly , 3% of patients will develop a metachronous (at a di ff erent time) colonic cancer. Up to a half of all patients with colorectal cancer will develop liver metastases at some point. Regular imaging of the liver (CT scan) and measurement of carcinoembryonic antigen (CEA) is designed to diagnose this early , in order to allow curative metastectomy . Optimum - follow-up pathways continue to be developed. NICE guide - lines recommend CT scans of the abdomen, pelvis and thorax as well as CEA measurements during the first 3 years after treatment of colon cancer with curative intent but identified no clinically important di ff erence in colorectal cancer-specific survival with a more intensive follow-up schedule compared with a less intensive follow-up. Palliative care About 20% of patients present with metastatic disease and about one-fifth of these patients are suitable for potentially curative management. For the rest, quality of residual life is the main outcome but it should be borne in mind that with the combination of interventions including chemotherapy , metastectomy , cytoreductive surgery and intraperitoneal eases chemotherapy some colonic disease may ‘convert to resectable’. For those whose disease remains incurable colonic surgery - may still be o ff ered, particularly if symptomatic. This may - be non-resectional (defunctioning stoma or internal bypass) or resectional (procedures detailed earlier but with a smaller segmental resection and less aggressive lymphadenectomy). Non-surgical techniques include palliative chemotherapy , stenting for obstruction, intraluminal laser, argon plasma coagulation and radiotherapy for bleeding and pain (especially in rectal cancers). Figure 77.11 Computed tomography scan of the liver showing mul tiple metastases from carcinoma of the colon (courtesy of Dr Rajpal Dhingsa, Nottingham University Hospitals, Nottingham, UK). Tumour stage Histological grade Degree of mucin secretin Presence of signet cells Venous invasion Perineural invasion Pushing versus in /f_i ltrative margin Tumour in /f_i ltrating lymphocytes Presence of MSI Gastrointestinal stromal tumours Gastrointestinal stromal tumours (GISTs) are extremely rare, constituting less than 0.1% of all colorectal tumours. They appear to arise from the interstitial cells of Cajal and are mainly due to a mutation in a specific gene called c-kit allows a specific marker to be used to diagnose most tumours as well as targeted chemotherapy with imatinib. Thirty per cent are malignant with mitotic rate, Ki-67 (>10%), size (>5 local invasion and cellularity the best indicators of malignant potential. Diagnosis is by CT or MRI and endoscopic biopsy . Surgical resection is the mainstay of treatment with imatinib for those tumours that are unresectable, have metastasised or recurred. Adjuvant imatinib may be used for tumours felt to be at high risk of recurrence. Carcinoid ‘Carcinoids’ are well-di ff erentiated neuroendocrine tumours of the colon and are part of a spectrum of disease with poorly di ff erentiated neuroendocrine carcinomas at the most aggres sive end of this spectrum. They constitute around 50% of all neuroendocrine tumours of the gut and about 5% of all colonic tumours. Fewer than 10% of colonic carcinoid tumours present with carcinoid syndrome (skin erythema, diarrhoea, cardiorespira tory symp toms) owing to release of hormones. Surgery remains the only potentially curative treatment and, since the possibility of metastatic disease is directly related to the size of the primary tumour, the extent of resection should be determined accord /uni00A0 ingly . Tumours greater than 2 cm require en bloc resection of adjacent mesenteric lymph nodes. In the midgut (the area receiving its blood supply from the superior mesenteric artery) /uni00A0 even lesions less than 1 cm have been shown to metastasise /uni00A0 and radical resection is also indicated. Small (<1 cm) hindgut tumours (the area receiving its blood supply from the inferior mesenteric artery) can be safely locally excised (see Chapters 74 and 76 ). Lymphoma Primary lymphoma of the colon is rare, accounting for less than 1% of all colonic malignancies. The caecum is the most common site of occurrence, usually with non-Hodgkin’s type lymphoma (NHL). Patients present with abdominal pain, a mass, change in bowel habit, per rectal bleeding, obstruction or intussusception. These tumours may occasionally perfo rate. The lack of specific complaints and rarity of intestinal obstruction probably accounts for the often delayed diagnosis. CT and colonoscopy with submucosal biopsy are required for diagnosis. Treatment is combination sur gery with systemic chemotherapy , although surgery alone may be considered adequate treatment for low-grade NHL disease that does not infiltrate beyond the submucosa. Santiago Ramon y Cajal , 1852–1934, Spanish neuroscientist, pathologist and Nobel prize winner (1906) for studies of cellular anatomy of the nervous system. Thomas Hodgkin , 1798–1866, pathologist, Guy’s Hospital, London, UK, described ‘Morbid appearances of the absorbent glands and spleen’ in 1832. Metastatic disease to the colon from other primary sites constitutes about 1% of all colorectal cancers. There is often a known primary , usually lung, ovary , breast, kidney , skin, stomach or hepatobiliary system tumours. In most cases multiple lesions are seen and one-third may be asymptomatic. . This The most common pathway of spread is through peritoneal seeding (typical of ovarian cancer), although haematological and lymphatic dissemination is described in breast and lung /uni00A0 cm), cancer and melanoma. Patients may present with obstruction, per rectal bleeding (especially melanoma), anaemia and weight loss. CT and colonoscopic biopsy are required for diagnosis and treatment should be individualised to patient symptoms and prognosis. Management Management Patients are frequently recommended a high-fibre diet and - bulk-forming laxatives, although the evidence for their e ff ec - tiveness in diverticulosis or after an attack of diverticulitis is limited. Antispasmodics may have a role if recurrent pain is - a problem. Acute diverticulitis has been traditionally treated with intravenous antibiotics and bowel r est. More recently , in recognition that diverticulitis may be a more inflammatory process than an infective one, many have advocated selective use of antibiotics. Essentially , antibiotic therapy may not be needed in immunocompetent people with uncomplicated diverticulitis who have no signs of systemic infection, as this may be a self-limiting condition. Uncomplicated disease should - be confirmed by CT . For disease complicated by a localised abscess, intravenous antibiotics and image-guided drainage is indicated. - Non-infective colitides Non-infective colitides Diverticular colitis Diverticular colitis is a clinicopathological entity distinct from acute diverticulitis (see Diverticular disease ). The term refers to colonic mucosal inflammation, resembling IBD, in a segment of colon a ff ected by diverticula. Symptoms of diarrhoea, pain and bleeding may occur, and the histology overlaps with that of IBD. It is usually self-limiting, with a short clinical course and low rate of recurrence. It is important to di ff erentiate diver ticular colitis from IBD to avoid further unnecessary tests and treatment. Localisation near to diverticula, a previous history of diverticulitis and rectal sparing should raise suspicion. Diversion colitis Diversion colitis is an iatrogenic process that occurs when a colon/rectum is defunctioned with a proximal stoma. Although the majority of patients with defunctioned bowel will develop typical changes of di ff use inflammation with friable mucosa and spontaneous bleeding, less than 50% will develop symp toms of lower abdominal pain, blood and mucus per rectum. The aetiology is likely to be multifactorial with alteration of the bacterial flora and a reduction in the bioavailability of short chain fatty acids (the predominant metabolic substrate of colonic m ucosa). Diagnosis is by endoscopy and treatment includes reassurance and, if feasible, restoration of the bowel continuity . See Chapter 75 . - Radiation colitis Radiation colitis refers to the characteristic acute and chronic morphological changes that occur following radiation treat - ment. Although most commonly occurring in the rectum (proctitis) these changes can a ff ect the colon if any portion falls within the radiation field. Acute inflammatory changes manifest a few days to 6 weeks after treatment, whereas chronic colonic changes leading to fibrosis and stenosis occur up to y ears later. Obstructive symptoms require appropriate radio - - logical and possibly endoscopic assessment and may lead to - resectional surgery . After resection care must be taken to ensure healthy non-irradiated bowel is used for any anastomosis. As - the rectum is the most commonly a ff ected part of the lar ge bowel, further details are given in Chapter 79 . Graft-versus-host disease colitis Graft-versus-host disease colitis (GVHD) is a common compli - cation occurring about 3–6 weeks after haematopoietic stem cell transplantation and is the result of severe immune-mediated toxicity against host cells. The patient develops diarrhoea and vomiting with colicky abdominal pain. Inflammation is e vident on endoscopy . Treatment is complex and di ffi cult. Once established the prognosis is poor. Drug-induced colitis A wide range of medications may induce colitis ( Summary box 77.10 ) and recognition is essential as cessation of the medication often leads to prompt resolution of symptoms. Patients with the DPYD ( dihydropyrimidine dehydrogenase ) gene mutation are particularly prone to colitis if treated with 5-FU during treatment for colon cancer. Dose reduction should be employed. Summary box 77.10 Drugs that may result in colitis /uni25CF /uni25CF - /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF - Ischaemic colitis Ischaemia of the colon typically results from thrombosis or embolism. Sudden embolic events leading to acutely ischaemic bowel present with severe pain out of proportion to the degree of peritonism, bloody diarrhoea, haemodynamic instability and shock. Resuscitation and laparotomy are required with Non-steroidal anti-in /f_l ammatory drugs Proton pump inhibitors and H2 antagonists Cardiac drugs (digoxin, diuretics, dopamine) Immunosuppressants Antibiotics (owing to increasing the likelihood of C. dif /f_i cile infection) Statins Chemotherapy Antidepressants (selective serotonin reuptake inhibitors) Anti-migraine drugs (ergotamine) Cocaine bowel ends. Mortality is extremely high. Thrombotic occlusion usually occurs in the context of global atherosclerosis. The presentation of this ischaemic coli tis tends to be less dramatic with abdominal pain, a raised white cell count and rectal bleeding. A plain abdominal radiograph may show ‘thumb-printing’ and endoscop y may demonstrate haemorrhagic oedema. The left colon and, in particular, the splenic flexure are usually the w orst a ff ected (the ‘watershed’ area of blood flow). Symptoms usually settle spontaneously . In some cases, ulceration at the splenic flexure associated with ischaemic colitis may heal with stricturing and present with subsequent large bowel obstruction. Bowel ischemia is a well-known but uncommon complica tion following both open and endovascular abdominal aortic aneurysm repair due to sacrifice of the inferior mesenteric artery . Operative procedures for diverticular disease Operative procedures for diverticular disease The aim of emergency surgery is to control peritoneal infection; indications are generalised peritonitis and failure to respond to optimum medical management. Laparotomy for diverticular disease in the acute setting has considerable risk with mortality in most series of 15%; in the case of faecal peritonitis, mortality approaches 50%. Traditionally laparotomy and thorough washout of con - - tamination are performed and then a choice has to be made between a Hartmann’s procedure (sigmoid resection with for - mation of a left iliac fossa colostomy and closure of the rectal stump; Figure 77.15 ) and resection with colonic washout and primar y anastomosis (with consideration of a defunctioning Figure 77.14 Colonoscopic view of right-sided diverticula. (From Niikura R, Nagata N, Akiyama J et al . Hypertension and concomitant arteriosclerotic diseases are risk factors for colonic diverticular bleed ing: a case–control study. Int J Colorectal Dis 2012; 27 : 1137–43.) loop ileostomy). Primary anastomosis should be used selec tively but is appealing in a young fit patient without gross contamination or overwhelming sepsis. There is evidence that simple defunctioning with a proximal stoma is associated with higher mortality than a resection of the a ff ected colon. There may be a role for emergency laparoscopy in divertic ular disease in expert hands. It allows assessment of the disease and in very selected cases a simple but thorough washout and drainage. The patient must have minimal comorbidity , be rel ativ ely stable, have no visible perforation and no gross faecal contamination. While this may avoid sigmoid resection in a select few , it remains controversial. Elective surgery is usually undertaken for management of complications. Diverticular fistulae can only be cured by resecting the a ff ected bowel, although a defunctioning stoma can ameliorate symptoms. In a colovesical fistula, once cancer has been ex cluded, the sigmoid can often be pinched o ff the bladder, the sigmoid colon resected and the bladder drained with an indwelling catheter for 7–10 days. If an anastomosis is performed, it is wise to place an omental pedicle between the bowel and bladder to prevent recurrent fistulation. These procedures can be technically challenging and ureteric stents may be advisable to reduce the risk of ureteric injury . Partial cystectomy may be required and assistance from a urological surgeon is often very helpful. Haemorrhage from diverticular disease should be distin guished from angiodysplasia. It usually responds to conser vative management and only occasionally requires resection. Where available, CT angiography is helpful to localise bleeding points and selective embolisation may control activ e bleeding. Rarely , colonoscopy may be necessary to localise the bleeding site. If the source cannot be located and bleeding continues, subtotal colectomy and ileostomy is the safest option. Indications for surgery in an elective setting, in the absence of complications of the disease, are controversial. There is undoubtedly a small number of patients with r ecurrent Edward Heyde , 1911–2004, American internist, published his findings on the association between aortic valve stenosis and angiodysplasia in a letter to the England Journal of Medicine in 1958. (with anastomosis). This could be performed laparoscopically in experienced hands with a likely swifter recovery as well as improved cosmesis. Cohort studies sug gest that of patients under 50 years old admitted with diverticulitis, 25% will have a further episode. The data may be used as an argument for o ff ering elective resection but equally indicate that 75% will not get another severe attack. Many surgeons would discuss the pros and cons of elective surgery after two emergency admis - sions, although comorbidities must be carefully considered. However, there is an increasing tendency to treat even patients with recurrent a ttacks of diverticulitis conservatively in the absence of complications. Summary box 77.12 Principles of surgical management of diverticular disease /uni25CF - /uni25CF /uni25CF /uni25CF - - Figure 77.15 Hartmann’s procedure with an oversewn rectal stump and an end left-sided colostomy following resection of the diseased segment of sigmoid colon. Hartmann’s procedure is often the safest option in an emergency setting Primary anastomosis (with or without proximal diversion) can be considered in selected patients Elective resection may be considered for recurrent attacks or complications Laparoscopy has advantages in the elective setting but use in the emergency setting is more controversial PHYSIOLOGY OF THE LARGE INTESTINE PHYSIOLOGY OF THE LARGE INTESTINE The principal function of the colon is absorption of water; approximately 1000 /uni00A0 mL of ileal content enters the caecum in faeces. Sodium absorption is e ffi ciently accomplished by an active transport system, while chloride and water are absorbed passively . Fermentation of dietary fibre in the colon by the normal colonic microflora leads to the generation of short chain fatty acids, which are an important metabolic substrate for colonic mucosa. Diversion of the faecal stream, denying the mucosa of this nutrition, may lead to inflammatory changes in the colon downstream (diversion colitis). Absorption of nutri ents, including glucose, fatty acids, amino acids and vitamins, can also take place in the colon. Colonic motility is variable. In general, faecal residue reaches the caecum 4 hours after a meal and the rectum after 24 hours. Passage of stool is not orderly because of mixing within the colon (see Chapter 73 ). Polyposis syndromes Polyposis syndromes Polyposis syndromes can be divided into familial adenomatous polyposis (FAP), attenuated familial adenomatous polyposis (AFAP), MUTYH -associated polyposis (MAP) and NTHL1 associated polyposis (NAP). Eldon John Gardner , 1909–1989, geneticist, The University of Utah, Salt Lake City , UT , USA, described this syndrome in 1950. FAP is defined clinically by the presence of more than 100 colorectal adenomas but is also characterised by duodenal adenomas and multiple extraintestinal manifestations ( Summary boxes 77.1 and 77.2 ). Over 80% of cases come from those with a positive family history . The remainder arise as a result of new mutations in the adenomatous polyposis coli ( APC ) gene on the long arm of chromosome 5. FAP is inher - ited as an autosomal dominant condition and is consequently equally likely in men and women. The lifetime risk of colorectal cancer is up to 100% in those with an APC gene mutation. FAP can also be associated with benign mesodermal tumours such as desmoid tumours and osteomas. Epidermoid cysts can also occur (Gardner’s syndrome); desmoid tumours in the abdomen spread locally to involve the intestinal mesentery and, although non-metastasising, they may become unresectable. Up to 50% of people with FAP have congenital hypertrophy of the retinal pigment epithelium (CHRPE), which can be used to screen a ff ected families if genetic testing is unavailable. Clinical features Polyps are usually visible on sigmoidoscopy by the age of 15 years and will almost always be visible by the age of 30 years. Regular endoscopic surveillance in a suspected family member should therefore commence at the age of 12–14 years, even if a genetic mutation has not been identified. Patients with mutations located between codons 1286 and 1513 of the APC gene generally have a worse prognosis with earlier disease onset than those with mutations outside this region. Germline mutations at codon 1309 are associated with the most severe disease. AFAP , also associated with APC gene mutation, is associated with fewer than 100 polyps and may not present until the fourth decade. If the diagnosis is made during adolescence, surgery is usu - ally deferred to the age of 17 or 18 years unless symptoms develop. Malignant change is unusual before the age of 20 years. Examination of blood relatives, including cousins , neph - ews and nieces, is essential; a family tree should be constructed, - and a register of a ff ected families maintained. Referral to a medical geneticist is essential. If over 100 adenomas are pres - ent at colonoscopy , the diagnosis can be made confidently ( Figure 77.3 ). Summary box 77.1 Features of FAP /uni25CF /uni25CF /uni25CF /uni25CF - Autosomal dominant inherited disease due to mutations of the APC gene More than 100 colonic adenomas are diagnostic Prophylactic surgery is indicated to prevent colorectal cancer Polyps and malignant tumours can develop particularly around the duodenal ampulla Summary box 77.2 Extracolonic manifestations of FAP /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Treatment The aim of surgery in FAP is to prevent the development of colorectal cancer. The surgical options are: 1 restorative proctocolectomy with an ileal pouch–anal anastomosis; 2 colectomy with ileorectal anastomosis (IRA); 3 total proctocolectomy and end-ileostomy . As patients are often young, most prefer to avoid a stoma, restorative proctocolectomy with ileal pouch–anal anastomosis has the advantage of removing the whole colon and rectum without the need for a permanent stoma (see Chapter 75 However, there is a pouch failure rate of approximately 10%. In addition, and particularly when a stapled anastomosis has been created, endoscopic surveillance is still required as malig nant change can occur in the ‘rectal cu ff ’ (the small strip of rectal mucosa between the pouch and the dentate line). Some advocate complete mucosectomy of this residual cu ff and a tion. In experienced hands, a laparoscopic approach is asso - ciated with swifter recovery , improved cosmesis and perhaps increased fecundity in women. For patients with relative rectal sparing (<20 polyps), total colectomy and IRA is an option to be considered, particularly as it is associated with less risk of sexual dysfunction in males and less infertility in females. Howe ver, the rectum requires regular endoscopic surveillance as up to 10% of patients will develop invasive malignancy in the rectum. In AFAP , patients may consider rectal preservation surgery on the understanding that their cancer risk is lower (around 2%) but still present. Proctocolectomy and ileostomy is the recommended option for patients with poor anal sphincter function, those who have already developed a r ectal cancer or those who wish to have a definitive single-stage procedure. Postoperative surveillance Because of the ongoing cancer risk, regular lifelong endoscopic surveillance of the rectum/pouch is important with biopsy of the rectal cu ff unless mucosal proctectomy has been performed. Endoscopy is also carried out to detect upper gastrointestinal tumours, particularly around the duodenal ampulla (see Chapter 67 ). A side-viewing duodenoscope is required. Despite surveillance, life expectancy is reduced because of extracolonic cancers and complications of desmoid tumours. MUTYH-associated polyposis The appearances of MAP can be similar to FAP but it is inherited as an autosomal recessive phenotype and predisposes individuals to multiple colonic polyps. If an APC pathogenic variant is not identified in an individual with colonic polyposis, molecular genetic testing of MUTYH should be considered. There is an increased risk of colorectal cancer of between three- and sixfold depending on the particular MUTYH mutation. Colonoscopy should be performed every 2 years. Colectomy is required when the number and/or characteristics of the polyps do not allow complete endoscopic resection or malignancy is diagnosed. Surveillance for duodenal adenomas is recommended. NTHL1 tumour syndrome NTHL1 tumour syndrome is a rare autosomal recessive cause of colorectal polyposis and increased lifetime risk for colorectal cancer. Colorectal polyps can be adenomatous, hyperplastic or sessile serrated. Management is similar to MAP . Peutz–Jeghers and juvenile polyposis syndrome Peutz–Jeghers syndrome (PJS) is an autosomal dominant genetic disorder characterised by the development of benign hamartomas in the gastrointestinal tract along with hyperpig - ). mented lesions on the lips and oral mucosa. The main clinical risks are small bowel intussusception in children and increased incidence of gastrointestinal malignancy in adult life (see - Chapter 74 ). Juvenile polyposis (JPS) is an autosomal dominant inher - ited condition that presents with hamartomatous polyps due to Figure 77.3 Familial adenomatous polyposis showing hundreds of adenomatous polyps. Endodermal derivatives Adenomas and carcinomas, particularly around the duodenal ampulla but also stomach, small intestine, thyroid and biliary tree Gastric fundic gland polyps Hepatoblastoma Ectodermal derivatives Epidermoid cysts Pilomatrixoma Congenital hypertrophy of the retinal pigment epithelium (CHRPE) Brain tumours Mesodermal derivatives Desmoid tumours Osteomas Dental problems tion characteristic of PJS is not present. Lynch syndrome (hereditary non-polyposis colorectal cancer) Lynch syndrome, previously known as hereditary non-polyposis colorectal cancer (HNPCC), is characterised by an increased risk of colorectal cancer and also cancers of the endometrium, ovary , stomach and small intestine, urinary tract, pancreas, prostate and kidney . It is an autosomal dominant condition caused by a mutation in one of four DNA mismatch repair genes ( MLH1 , MSH2 , MSH6 and PMS2 ). These genes, when func tioning normally , code for mismatch repair (MMR) proteins, which repair sporadic mutations that occur in other genes. If faulty , mutations accumulate in other key genes, leading to characteristic repea t sequences of DNA, termed microsatellite instability (MSI), and acceleration of the adenoma–carcinoma sequence. Thus individuals with an MMR gene mutation tend to develop colorectal polyps at an early age (before the age of 50 years) that quickly become cancerous. Not everyone with a mutation develops cancer; the lifetime risk is 80%. Most cancers develop in the proximal colon. Females have a 30–50% lifetime risk of developing endometrial cancer. Diagnosis Lynch syndrome was historically diagnosed based on a family history of cancer and the clinical parameters set out in the Amsterdam ( Summary box 77.3 ) and Bethesda criteria. Recent advances in immunohistochemistry allow for MMR proteins or MSI to be accurately identified in all colorectal tumours with subsequent genetic testing in patients and fami lies of those proven positive. Summary box 77.3 Amsterdam II criteria /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Because of the accelerated pathway from adenoma to cancer in Lynch syndrome those with a gene mutation should be o ff ered 2-yearly endoscopic surveillance from age 25 years ( MLH1 and MSH2 carriers) or 35 years ( MSH6 carriers). PMS2 carriers should be o ff ered 5-yearly screening beginning at age 35 years (see Further reading ). For patients with pol yps that cannot be managed with endoscopic polypectomy or those who develop a cancer, an extended colectomy ( MLH1 and MSH2 carriers) should be considered. The benefit of screening other areas of the gastrointestinal tract is unclear Henry Thompson Lynch , 1928–2019, physician and geneticist, Omaha, NE, USA, first presented his findings of a family with a strong history of colorectal cancer without polyposis in 1964. with the 2019 Manchester Consensus (see Further reading ). Three or more family members with a Lynch syndrome-related cancer (colorectal, endometrial, small bowel, ureter, renal pelvis), one of whom is a /f_i rst-degree relative of the other two Two or more successive affected generations At least one tumour diagnosed before the age of 50 years FAP excluded Tumours veri /f_i ed by pathological examination TUMOURS OF THE LARGE INTESTINE Benign TUMOURS OF THE LARGE INTESTINE Benign The term ‘polyp’ is a clinical description of any protrusion of the mucosa. It encompasses a variety of histologically di ff erent tumours ( Table 77.1 ). Polyps can occur singly , synchronously in small numbers or as part of a polyposis syndrome. Metaplastic polyps Metaplastic or hyperplastic polyps are common and are gener ally considered benign. Recently certain subtypes have been recognised to have malignant potential. Sessile serrated lesions and hyperplastic polyps ≥ 10 /uni00A0 mm in diameter are associated with KRAS / BRAF mutation that may lead to methylation of tumour-suppressing genes, dysplasia and malignancy along what is termed the ‘serrated pathway’. Such polyps should be removed and follow-up colonoscopy arranged ( Figure 77.1 John Law Augustine Peutz , 1886–1968, Chief Specialist for Internal Medicine, St John’s Hospital, The Hague, The Netherlands. Harold Joseph Jeghers , 1904–1990, Professor of Internal Medicine, New Jersey College of Medicine and Dentistry , Jersey City , NJ, USA. - - Adenomatous polyps Adenomatous polyps are the most common polyps with malignant potential. The risk of malignancy is dependent on ). histology , morphology and size. Tubular adenomas have the lowest risk, with increasing risk as villous features predominate. Sessile and particularly depressed lesions have more malignant potential than pedunculated lesions ( Figure 77.2 ). The risk of malignant change increases with size, almost one-third of large (>3 /uni00A0 cm) colonic adenomas will have an area of invasive malig - nancy . Size is easily assessed endoscopically , which, alongside pit pattern and morphological classification, aids management. If felt appropriate and safe to resect endoscopically , various techniques are available, including hot or cold snar e poly - pectomy for the most common smaller pedunculated lesions. Larger or flatter polyps may require infiltration of a solution to ‘raise’ the polyp before snare resection. The area of the polyp should be tattooed to facilitate later endoscopic or laparoscopic localisa tion of the site of the polyp. Failure of submucosal injection to elevate a polyp is suggestive of malignancy . In these circumstances, the site should be tattooed. A biopsy should not be taken if referral for endoscopic mucosal resection or endoscopic submucosal dissection is being considered. Such techniques carry a risk of colonic perforation and should only TABLE 77.1 Classi /f_i cation of intestinal polyps. In /f_l ammatory In /f_l ammatory polyps (pseudopolyps in ulcerative colitis) (see Chapter 75 ) Hamartomatous Peutz–Jeghers polyp Juvenile polyp Serrated polyps Hyperplastic polyp (serrated lesions) Sessile serrated lesion Sessile serrated lesion with dysplasia Traditional serrated adenomas Mixed polyp Adenoma Tubular Tubulovillous Villous Malignant polyp Adenocarcinoma Colorectal Colonoscopy at cancer 1 year No. Site check at 2–6 months and then after a further 20 mm 12 months non-pedunculated Colonoscopy colorectal polyp with Yes. complete excision One-off colonoscopy at 3 years No. Participate in bowel cancer screening programme when invited High-risk /f_i ndings* Yes. One-off colonoscopy at 3 years Figure 77.1 Recommendations for polyp follow-up. *Two or more premalignant polyps including at least one advanced polyp (serrated polyp >10 mm or with dysplasia, adenoma more than 10 mm in size or with high-grade dysplasia); or /f_i ve or more premalignant polyps. (Adapted from Rutter MD, East J, Rees CJ et al . British Society of Gastroenterology/Association of Coloproctology of Great Britain and Ireland/Public Health England post-polypectomy and post-colorectal cancer resection surveillance guidelines. Gut 2020; 69 : 201–23.) be performed by an experienced endoscopist. Rectal adenomas may also be treated by endoscopic or transanal resection (see Chapter 79 ). Polyp surveillance After successful endoscopic removal of polyps, there is a risk of further polyp development; however, the risk of subsequent development of colorectal cancer is low . The need for and frequency of follow-up surveillance endoscopy is dependent on polyp morphology , number and size, age and comorbidity of the patient, presence of a family history and accuracy and completeness of the index test. These factors allow polyps to be divided into low , intermediate and high risk. Recent guidelines ( Figure 77.1 ) published by the British Society of Gastroenter ology have identified patients at high risk needing follow-up colonoscopy as those with either: /uni25CF two or more premalignant polyps, including at least one advanced colorectal polyp (defined as a serrated polyp ≥ 10 /uni00A0 mm in size or containing any grade of dysplasia or as an adenoma ≥ 10 /uni00A0 mm in size or containing high-grade dysplasia); or /uni25CF five or more premalignant polyps. Figure 77.2 Pedunculated polyp of the large intestine showing tubulovillous changes at the apex and normal colonic mucosa at the base (courtesy of Dr Philip Kaye, Nottingham University Hospitals, Nottingham, UK). Treatment Treatment For sigmoid volvulus the initial management is non-operative decompression using either a rigid sigmoidoscope or a colono - scope. Direct vision allows assessment of mucosal viability and derotation. With successful derotation a well-lubricated flatus tube should be inserted and left for 2–5 days. Bloody bowel It contents or discoloured mucosa suggest ischaemia and the need f or urgent surgery . Attempted derotation in this situation should be abandoned as it could lead to circulatory collapse and death. Careful consideration of definitive surgery on a case-by-case basis in this, often elderly and frail, patient group is required. - Although they would be subject to significant perioperative risk there is a very high recurrence rate f or sigmoid volvulus. Such surgery should involve at least resection of the whole of the sigmoid colon and can be carried out laparoscopically . Given that there is very little need for colonic mobilisation and a large utility incision is required because of the bowel size, some of - the benefits of a laparoscopic approach are negated. It is there - fore reasonable to carry out surgery through a minilaparotomy incision with the same recovery outcomes. An alternative to surgical resection in the very unfit patient is a percutaneous endoscopic colostomy , using a colonoscope to place a drainage tube through the abdominal wall into the sigmoid to fix the bowel in an untwisted position. In the emergency situation where there is evidence of necrosis it may be wise to ligate the mesenteric vessels before untwisting the volvulus to theoretically avoid the systemic release of ischaemic toxins. It may also be prudent to a anastomosis. Instead, a Hartmann’s-type approach or a Paul– Mikulicz double-barrelled stoma should be considered. For caecal volvulus endoscopic decompression is often unsuccess ful and leads to treatment delay . Instead, urgent right hemicol ectomy is indicated. Figure 77.17 Plain abdominal radiograph showing colonic distension associated with a sigmoid volvulus (courtesy of Dr Rajpal Dhingsa, Nottingham University Hospitals, Nottingham, UK). Types of colostomy Types of colostomy Loop colostomy Loop stomas are most commonly used to temporarily divert the faecal stream; for instance, to protect an anastomosis (usually by a loop ileostomy) following traumatic injury to the rectum, to facilitate the operative treatment of a high anal fistula, for incontinence and to defunction an obstructing void low rectal cancer prior to long-course chemoradiotherapy . A mobilised loop of colon is brought out onto the anterior abdominal wall. Once the abdomen has been closed, the - colostomy is opened and the edges of the colonic incision are - sutured to the adjacent skin margin ( Figure 77.18 ). A rod or bridge is sometimes placed under the loop to prevent retrac - tion in the early postoperative period, being removed after a few days. Colostomy function should be expected in 2–7 days after operation. Figure 77.18 Loop colostomy with a bridge. porary stoma was constructed, the colostomy can usually be closed without recourse to a laparotomy/laparoscopy . Conven tionally a water-soluble contrast enema is performed to assess the distal bowel before closure, particularly for pelvic anasto moses. A pproximately 25% of temporary diverting stomas are never closed because of complications or changes in medical comorbidity . End-colostomy This is formed after an abdominoperineal excision of the rectum or as part of a Hartmann’s procedure, bringing the divided colon through a left iliac fossa trephine in rectus abdominis and the skin. The colonic margin is then sutured usually flush or slightly everted on the adjoining skin ( 77.19 ). Double-barrelled colostomy (Paul–Mikulicz) Occasionally , when resection of a section of colon has occurred but the patient is too ill to undergo a safe reanastomosis it is possible and appropriate to bring up both ends of the bowel to the abdominal wall (see Volvulus ). This aids subsequent closure as the ends can simply be mobilised locally and reanas tomosed rather than the patient requiring a relaparotomy . Summary box 77.15 Stomas /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Stoma output is collected in disposable adhesive bags. Colos - - tomy appliances are simply changed as necessary . A wide range of such bags is currently available. In most hospitals, a stoma - care service is available to o ff er advice to patients, to acquaint them with the latest appliances and to provide the appropriate psychological and practical help. Figure 77.19 A colostomy in the left iliac fossa. May be colostomy or ileostomy May be temporary or permanent Temporary or defunctioning stomas are usually fashioned as loop stomas An ileostomy is spouted; a colostomy is /f_l ush or slightly everted Ileostomy ef /f_l uent is usually liquid whereas colostomy ef /f_l uent is usually solid Ileostomy patients are more likely to develop /f_l uid and electrolyte problems An ileostomy is usually sited in the right iliac fossa End-colostomy is usually sited in the left iliac fossa Whenever possible patients should be counselled and sited by a stoma care nurse before their operation VASCULAR ANOMALIES OF THE INTESTINE Angiodysplasia VASCULAR ANOMALIES OF THE INTESTINE Angiodysplasia Angiodysplasia is a vascular malformation that commonly causes haemorrhage from the colon in patients over the age of 60. The malformations consist of dilated tortuous submucosal veins. Clinical features In the majority of cases, the symptoms are subtle and patients can present with anaemia. About 10–15% have brisk bleeds, which may present as melaena or significant rectal bleeding. Many patients in whom rectal bleeding has been attributed to - diverticular disease have probably bled from angiodysplasia. - There is an association with aortic stenosis (Heyde’s syndrome). Investigation Colonoscopy may show the characteristic lesion in the right colon. The lesions are only a few millimetres in size and appear as reddish, raised areas at endoscopy . CT angiography shows the site and extent of the lesion by a ‘blush’ of contrast, provided bleeding is more rapid than 1 /uni00A0 mL/min. If this fails, a 99m Tc-labelled red cell scan may confirm and localise the source of haemorrhage. New In the context of a massive lower gastrointestinal bleed the first principle is to stabilise the patient. Following this, the bleeding needs to be localised. CT angiography allows not only localisation if bleeding is rapid but also therapeutic embolisation. If angiography fails or is unavailable careful colonoscopy (with copious lavage) may allow cauterisation to be carried out and an argon laser can be helpful. In severe uncontrolled bleeding, surgery becomes necessary . If preoperative localisation has not been successful, on-table colonoscopy is carried out to confirm the site of bleeding. Angiodysplastic lesions are sometimes demonstrated by trans- illumination through the caecum. If it is still not clear exactly which segment of the colon is involved a subtotal colectomy may be necessary . The management algorithm in Summary box 77.13 is adapted from the diagnosis and management acute lower gastrointestinal bleeding guidelines from the British Society of Gastroenterology . Summary box 77.13 Management of acute lower gastrointestinal bleeding /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Patients with active bleeding and features of hypovolaemic shock CT angiogram and embolisation Bleeding treated: inpatient colonoscopy Bleeding continues: consider therapeutic endoscopy or surgery Patients without features of hypovolaemic shock Signi /f_i cant bleeding: inpatient colonoscopy and consider oesophagogastroduodenoscopy; if normal consider capsule endoscopy, CT angiogram, nuclear medicine scanning Minor bleeding: arrange outpatient investigations All patients: consider withholding anticoagulants and transfuse blood products as required VOLVULUS VOLVULUS A volvulus is a twist of the intestine and the mesentery that supplies it ( Figure 77.16 ). It is most commonly seen in the sigmoid colon, where elongation of the colon and mesentery with a narrow posterior attachment exists in some patients. can, however, occur in patients with a hypermobile caecum and rarely in the transverse colon. Patients with sigmoid volvulus tend to be elderly and institutionalised; however, in West African countries it is more commonly seen in younger patients. Patients presenting with a caecal volvulus are usually younger and otherwise well. Predisposing factors include adhe sions, gastric banding, pelvic masses and pregnancy .