Dr. Donald J. Fleischli: This 47-year-old woman entered the hospital complaining of intermittent cramps and diarrhea during the past year. A typical attack lasted three to four days and consisted of five to ten episodes of severe lower-abdominal cramps and urgency, relieved promptly by defecation, which often produced only small amounts of loose watery stool containing mucus but no blood. Between attacks she was asymptomatic for periods of two to three weeks. She had been in Mexico nine months prior to admission and in Puerto Rico one week prior to admission, however her complaints antedated these trips.
Results of physical examination were normal. There was no abdominal tenderness. White blood cell count, hemoglobin level, and urinalysis findings were normal. The erythrocyte sedimentation rate was elevated. Sigmoidoscopy revealed several 5mm discrete shallow ulcers near the rectosigmoid junction. Several stool examinations gave negative results for blood, ova, and parasites. A later specimen