A 26-year-old woman was admitted to the hospital because of bouts of abdominal pain with vomiting, diarrhea, and hematochezia.She had received a diagnosis of the irritable bowel syndrome several years earlier. Her disorder was characterized by episodic abdominal pain in the left lower quadrant, without diarrhea, constipation, or other symptoms. Increased dietary intake of fiber and antispasmodic medication resulted in transient improvement. An abdominal and pelvic ultrasonographic examination, performed three and a half years before admission, showed no abnormalities. A barium-enema procedure, performed 12 days later, showed considerable spasm, predominantly in the right side of the transverse colon.Nineteen months before admission, pain unrelated to menses recurred in the left lower abdominal quadrant. The results of a rectal examination and a flexible sigmoidoscopic study, performed to a level of 55 cm, were normal. Six days later, a computed tomographic (CT) scan of the abdomen showed a cluster of cysts, 3 to 4 cm in diameter, in the left ovary and a small cluster in the right ovary. Ten months before admission, shortly after the patient began taking tetracycline for acne vulgaris, she had pain in the left lower quadrant with diarrhea, which lasted for one week. A test for Clostridium difficile toxin was negative. The discontinuation of tetracycline and the resumption of treatment with antispasmodic medication resulted in temporary improvement.One month before admission, the patient began to have severe lower abdominal pain, with intermittent nausea, vomiting, and diarrhea. Abdominal radiographs obtained at another hospital showed no important abnormalities. Four days later, the pain, accompanied by nausea, occasional vomiting, and hematochezia, worsened as her menses began. Examination showed mild upper abdominal tenderness; the diarrhea resolved spontaneously. Three weeks before admission, the patient went to another hospital because of increasing abdominal pain; abdominal radiographs showed no change. On the following day, she consulted her physician because of persistent abdominal pain, with intermittent rectal bleeding during the passage of solid stools. The blood count and erythrocyte sedimentation rate were normal, and a test for chorionic gonadotropin was negative. An upper gastrointestinal series with a small-bowel study (Fig.