Origin of fistulas in Crohn's disease.

In 236 resection specimens of Crohn's disease (127 first excisions and 109 reexcisions) there were 60 specimens with fistulas (excluding anal fistulas): 44 in first excisions and 16 in reexcisions. In primary excisions, 36 fistulas arose in the ileum, three in the colon and five in the ileocecal valve. The majority were located either at the proximal end of a stricture (62%) or within a stricture (31%); four cases (7%) were not associated with strictures. In reexcision specimens, ten fistulas arose at the bowel anastomosis, four arose in the ileum in association with strictures, and two were of doubtful origin. Only four fistulas in primary excisions drained to the skin whereas seven did so in reexcisions.