Rectal biopsy in patients presenting to an infectious disease unit with diarrhoeal disease.

The role of sigmoidoscopy and rectal biopsy was investigated in patients referred to an infectious diseases unit with diarrhoea. Seventy-four patients were studied. Nine patients (12%) had inflammatory bowel disease, either ulcerative colitis or Crohn's disease. Thirty-six patients (48%) had infective diarrhoea. A wide variety of conditions accounted for the diarrhoea in the remaining patients. Sigmoidoscopy was abnormal in 25 patients and rectal biopsy in 56. The abnormalities in rectal mucosal histology were classified into six grades. Some patients with infective diarrhoea showed rather characteristic histological changes which may be of diagnostic value. Eight showed features which suggested a diagnosis of inflammatory bowel disease. However, repeat rectal biopsy in the convalescent period showed a striking improvement in the patients with infective diarrhoea. In contrast, the histological changes persisted in the patients with inflammatory bowel disease. Repeat rectal biopsy may be essential before making a firm diagnosis of inflammatory bowel disease in some patients who present with diarrhoea and apparently typical histological changes.