Anatomic basis for delayed diagnosis of appendicitis.

Gangrene or perforation of the appendix is often caused by failure to make an early diagnosis of appendicitis. Variability in the anatomic location of the appendix can be responsible for atypical manifestations of appendicitis and diagnostic errors. Over a 52-month period, 125 appendectomies were done for suspected appendicitis at a military hospital. After excluding cases in which the location of the appendix was not provided, 106 cases were available for review. Fifteen patients (14%) did not have appendicitis. The appendix was found in the true pelvis, was behind the ileum or ileocolic mesentery, or was both retrocolic and retroperitoneal in 11 of 16 patients (69%) with gangrenous or perforative appendicitis. In contrast, the appendix was in one of these three sites in only four of 75 patients (5%) with simple appendicitis (P less than .001). Both physicians and patients were responsible for diagnostic delays, but the paucity of symptoms and signs in patients with a "hidden" appendix was the most likely cause of failure to diagnose appendicitis before perforation.