Escherichia coli O157 infection mimicking acute appendicitis: usefulness of computed tomography for differential diagnosis

A 19-year-old man was admitted to our hospital with acute abdominal pain in the right lower quadrant. He had had mild diarrhea, of 1 day’s duration, 2 days before admission. Although physical findings were consistent with a diagnosis of acute appendicitis, computed tomography findings showed marked wall thickening from the ascending colon to the cecum, findings which were similar to those in patients with hemorrhagic colitis due to Escherichia coli O157. Instead of emergency laparotomy, the patient was treated with antimicrobial agents, which led to rapid recovery. Diagnosis of intestinal infection due to E. coli O157 was established later, as serum antibody against lipopolysaccharide of E. coli O157 was positive. E. coli O157 infection should be included in the differential diagnosis of diseases that exhibit marked wall thickening of the right colon on CT in patients with acute abdominal pain in the right lower quadrant who have mild transient diarrhea.