Review the normal anatomy and variable position of the appendix. Discuss the pathogenesis, clinical manifestations, and imaging findings characteristic of acute appendicitis and various other diseases of the appendix. Clarify important radiological differences between acute appendicitis and other appendiceal abnormalities.

Anatomy The appendix is a blind-ended, vermiform (worm-like) structure averaging 6-9cm long in adults. It arises from the cecum of the large intestine and is suspended from the terminal ileum by the mesoappendix, a triangular fold of mesentery containing lymphoid tissue and blood vessels (Figure 1). The anatomy of the appendix predisposes it to inflammation. Appendicitis Acute appendicitis is the most common disease of the appendix—the lifetime risk of developing it is 8.6% for males and 6.7% for females [1]. Acute appendicitis most frequently results...

Stump appendicitis Stump appendicitis is a post-appendectomy complication where inflammation occurs in the appendiceal remnant (Figure 5). Although the exact mechanism is unclear, stump appendicitis is thought to occur due to poor blood supply or obstruction of the lumen of the remaining stump [3]. All reported cases of stump inflammation are greater than 5mm in length, thus surgical literature generally recommends leaving a stump <5mm [1,3]. Foreign body appendicitis Foreign bodies are capable of obstructing the lumen of the appendix to cause inflammation (Figure 6)....

An array of diseases of the appendix can mimic the symptoms and/or imaging featuresthat are typical of acute appendicitis. An abnormal appendix may signifyother inflammatory or neoplastic conditions.It is important for the radiologist to be able to differentiate these abnormalities from acute appendicitis for the purpose of accurate diagnosis and appropriate management.

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