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Aetiology There is no unifying hypothesis regarding the aetiology of acute appendicitis. Decreased dietary fibre and increased consumption of refined carbohydrates may be important. As with colonic diverticulitis, the incidence of appendicitis is lowest in soc...

Appendicitis in pregnancy Appendicitis appears to be less common in pregnant than in non-pregnant females; however, it is the most common extrauterine acute abdominal condition in pregnancy , with an incidence of 0.5–1 per 1000 pregnancies. Appendicitis is sl...

Differential diagnosis Although acute appendicitis is the most common abdominal surgical emergency , the diagnosis can be extremely di ffi cult at times. There are a number of common conditions that it is wise to consider carefully and, if possible, exclude. T...

Epithelial tumours of the appendix Epithelial neoplasms are found in 0.6% of appendicectomy specimens. Numerous classification systems have been proposed, leading to much confusion and di ffi culty when comparing treatment modalities and outcomes. Following a mo...

FURTHER READING Ansari N, Chandrakumaran K, Dayal S et al . Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in 1000 patients with perforated appendiceal epithelial tumours. Eur J Surg Oncol 2016; 42 : 1035–41. Carr NJ, Cecil TD, Mohamed F e...

Goblet cell carcinoma Goblet cell carcinomas (GCCs) of the appendix are a rare vari ant, accounting for less than 5% of appendix tumours. They display both neuroendocrine and glandular di ff erentiation and are not considered true NETs. They ma y be classified...

Gross anatomy The position of the base of the appendix is constant, being found at the confluence of the three taeniae coli of the caecum, which fuse to form the outer longitudinal muscle coat of the appendix. At operation, use can be made of this to find ...

High-grade and invasive neoplasms Appendiceal mucinous tumours displaying high-grade dysplasia are classified as high-grade appendiceal mucinous neoplasm (HAMN). Mucinous tumours with infiltrative inva - sion are classified as mucinous adenocarcinoma and may be w...

INTRODUCTION The importance of the vermiform appendix in surgery arises primarily from its propensity for inflammation, which results in the clinical syndrome known as acute appendicitis. Acute appendicitis is the most common cause of an ‘acute abdomen’ in yo...

Investigation The diagnosis of acute appendicitis is essentially clinical; however, a decision to operate based on clinical suspicion alone can lead to the removal of a normal appendix in 15–30% of cases. The premise that it is better to remove a normal appe...

Investigations The investigation of a patient with PMP should include a high-resolution CT scan of the abdomen and pelvis with oral and intravenous contrast. A full colonoscopy should be performed to exclude a primary colorectal cancer. Laparos copy may prov...

Learning objectives To understand: The aetiology and surgical anatomy of acute appendicitis • The clinical signs and differential diagnoses of • appendicitis The investigation of suspected appendicitis •

Low-grade neoplasms Most epithelial tumours of the appendix are classified as LAMNs. These lesions demonstrate minimal cytological Laura H Tang , contemporary , pathologist, Memorial Sloan Kettering Hospital, New Y ork, NY , USA. atypia and are characterised b...

Management of an incidental or

Microscopic anatomy The appendix varies considerably in length and circumference. The average length is between 7.5 and 10 /uni00A0 cm. The lumen is irregular, being encroached on by multiple longitudinal folds of mucous membrane lined by columnar cell intesti...

NEOPLASMS OF THE APPENDIX AND PSEUDOMYXOMA PERITONEI Tumours of the appendix may occur in up to 0.97 per 100 /uni00A0 000 of the population. NETs account for approximately 30% of appendix neoplasms while epithelial tumours account for most other cases. Epith...

Neuroendocrine tumours of the appendix NETs of the appendix are slightly more common in females and have an overall incidence of 0.15–0.6 per 100 /uni00A0 000 per year. They arise in subepithelial neuroendocrine cells ( Figure 76.16 and the majority (70%) are...

Pathology Obstruction of the appendiceal lumen seems to be essential for appendiceal perforation. However, in many cases of early appendicitis, the appendix lumen is patent despite the presence - of mucosal inflammation and lymphoid hyperplasia. Occa - siona...