Appendicitis and beyond: a pictorial review of various appendiceal abnormalities

Acute appendicitis is the most common disease of the appendix. However, the differential diagnosis for an abnormal appendix includes other conditions that often present with symptoms and imaging features that overlap with acute appendicitis. In this pictorial essay, we review the normal anatomy of the appendix and outline the pathogenesis, clinical manifestations, and imaging findings that are characteristic of acute appendicitis and other less common appendiceal abnormalities. Inflammatory/non-neoplastic processes including appendiceal diverticulitis, stump appendicitis, foreign body appendicitis, Crohn's appendicitis, and appendiceal hernias are discussed. Neoplastic considerations include appendiceal neuroendocrine tumors, mucinous and non-mucinous (colonic type) epithelial neoplasms, and lymphoma. It is important for the radiologist to be able to differentiate these alternative diagnoses for the purpose of directing appropriate patient management.