Polyps relevant to the rectum

Polyps relevant to the rectum

Hyperplastic polyps These are small, pinkish, sessile polyps, 2–4 /uni00A0 mm in diameter and frequently multiple. They are usually an incidental finding, unless larger in size, when full colonoscopy is warranted to exclude hyperplastic polyposis syndrome. Tubular adenomas Tubular adenomas, or mixed tubulovillous adenomas, are the most common type of polyp. They have the potential to turn malignant, particularly if over 1 /uni00A0 cm in diameter. Villous adenomas These have a characteristic frond-like appearance. They may be very large, occupying much of the circumference of the rectum. These tumours have an increased tendency to become malignant. Rarely , the profuse mucus discharge from these tumours, which is rich in potassium, causes electrolyte and fluid losses. Serrated adenomas - These polyps are more commonly found in the right colon but may be present in the rectum. They are typically sessile lesions that have a distinct microscopic architecture and can give rise to cancers through an alternative ‘serrated’ pathway . Familial adenomatous polyposis Familial adenomatous polyposis (FAP) is an autosomal domi - nant inherited condition characterised by the development of multiple rectal and colonic adenomas around puberty . It is due to mutation in the adenomatous polyposis coli ( APC ) . gene, allowing genetic testing in the 75% of families in which a mutation can be identified. A colonoscopy and biopsy will in - ano confirm the diagnosis. As this condition is premalignant, total colectomy is usually recommended within 10 years of disease onset. This may take the form of panproctocolectomy with permanent ileostomy . Rectal preservation may be an option if the rectal polyp load is not too severe, with colectomy and ileorectal anastomosis, but continuous rectal surveillance for synchronous polyps will be required. The alternative, if resto - ration of gastrointestinal continuity is desired, is to undertake restorative proctocolectomy with ileal pouch–anal anastomosis (see Chapter 77 ). Inflammatory pseudopolyps These are oedematous islands of mucosa. They are usually associated with colitis in the UK, but most inflammatory diseases (including tropical diseases) can cause them. They are more likely to cause radiological di ffi culty , as the sigmoido - scopic appearance is usually associated with obvious signs of active or quiescent inflammation. Juvenile polyp This is a bright red, glistening pedunculated sphere (‘cherry tumour’) that is found in infants and children that may persist into adult life. It can cause bleeding or pain if it prolapses during defecation. It often separates spontaneously but can be removed easily with forceps or a snare. A solitary juvenile polyp has virtually no tendency to malignant change but should be treated if symptomatic. Histological features typically consist (a) (c) rectal cuboidal epithelium ( Figure 79.13 ). The rare autosomal dominant inherited syndrome juvenile polyposis does carry an incr eased risk of malignancy . It is characterised by multiple polyps and a positive family history .

Figure 79.13 Microscopic appearance of a juvenile polyp (courtesy of Professor Kieran Sheahan, St Vincent’s University Hospital, Dublin, Ireland). Lesion Mucosa Muscularis mucosa Submucosa Muscularis propria Figure 79.14 Endoscopic mucosal resection. The polyp is identi /f_i ed diathermy snare is passed over the raised lesion (c) to achieve complete excision