Report of a Case. A 36-year-old homosexual man with acquired immunodeficiency syndrome (AIDS) presented for evaluation of a 4-day history of diffuse colicky pain, later located in the right lower quadrant of the abdomen. Two months earlier MAC organisms had been isolated from blood cultures, and the patient was receiving clarithromycin, ethambutol hydrochloride, ciprofloxacin hydrochloride, and clofazamine. His most recent CD4 cell count had been 0.03x10⁹/L. Physical examination revealed an axillar temperature of 36.6°C (rectal temperature, 38°C), mild abdominal distention with hepatosplenomegaly, absence of bowel sounds, diffuse abdominal tenderness, and a positive psoas sign. The white blood cell count was elevated over baseline at 3.2x107L, with 0.74 neutrophils and 0.18 band cell forms. An x-ray