Bowel diversion should be used with caution in stenosing anal Crohn's disease.

Proximal diversion has commonly been used for severe perianal Crohn's disease in an attempt to relieve local symptoms, whether the primary intestinal disease is in the colon or small bowel. Two patients are presented in whom diversion led to severe symptomatic disease in the previously normal defunctioned bowel. In each case the development of colonic disease was associated with increasing anal stenosis leading to retention of purulent fluid within the bowel lumen. Faecal stream diversion should be used with caution in stenosing anal Crohn's disease.