Significant association of strictures and internal fistula formation in Crohn's disease

Intestinal inflammation in Crohn's disease (CD) may be complicated by the o ccurrence of strictures and fistulae. The pathogenesis of fistula formation is unknown. We therefore wanted to determine whether mechanical factors mi ght contribute to the development of fistulae. Furthermore, we tried to def ine the path of internal fistulae through the muscular layer. For this purp ose, surgical resection specimens from 42 consecutive patients with CD were prospectively studied. In gross examination the whole bowel was cut into c ircumferential cross sections 0.3 cm thick. Abnormal areas were histologica lly examined. Strictures were found in 38 patients (90.5%), and fistulae we re observed in 27 (64.3%) patients. In 11 (40.7%) specimens fistulae were f ound within a stricture, in 15 (55.6%) at the proximal end, and in 1 (3.7%) no stricture was found. In 7 (25.9%) cases with fistulae, herniated mucosa was found within the muscularis propria or the subserosa. In 7 (25.9%) cas es a blood vessel was identified near a fistula traversing the muscularis p ropria. From these findings we conclude that that mechanical factors may co ntribute to fistula formation. This is further supported by the fact that f istulae appear to traverse the muscular layer along piercing vessels.