Incidence and sonographic diagnosis of bacterial ileocaecitis masquerading as appendicitis

533 consecutive patients with suspected acute appendicitis or appendiceal mass were examined by ultrasonography to distinguish acute appendicitis from bacterial enteritis. In 61 (11.4%) ultrasonography revealed the characteristic picture associated with bacterial enteritis of the ileocaecal region--enlarged mesenteric lymph nodes and mural thickening of the terminal ileum and caecum--but no image of the appendix. In 41 of these a bacterial infection was confirmed: infection due to Yersinia enterocolitica in 21, Campylobacter jejuni in 15, Salmonella B in 3, Salmonella C in 1, and Yersinia pseudotuberculosis in 1. In the other 20 bacteriological tests were negative (10) or not done (10). Oral barium studies, done in 15 patients, showed thickening of the terminal ileum in all of them. Only 22 of the 61 patients had diarrhoea. Yersinia enteritis clinically simulated an appendiceal mass in 17 of 22 patients, 6 of the 61 patients underwent surgery, and in all of them the appendix removed was normal. The other 55 patients recovered with conservative treatment. In 26 a planned appendicectomy was cancelled because of the sonographic findings. Bacterial enteritis limited to the ileocaecal region (bacterial ileocaecitis) seems to be responsible for an appreciable number of unnecessary appendicetomies. It has characteristic sonographic features that distinguish it from appendicitis.