Obliterative muscularization of the small bowel submucosa in Crohn disease- A possible mechanism of small bowel obstruction

Context.-The pathology of small bowel obstruction in Crohn disease has not been studied extensively. Stricture formation has been attributed mainly to fibrosis, although muscularization of the submucosa has been discussed pre viously. Objective.-To identify additional pathologic changes in Crohn disease that could be involved in the formation of strictures. Design.-We reviewed 50 ileal resections from patients with Crohn disease. T he histopathologic slides were reviewed initially without knowledge of the macroscopic or clinical findings. We identified an unusual muscular prolife ration that we refer to as obliterative muscularization of the submucosa, d efined as a thick and continuous muscle layer from the mucosal base to the muscularis propria that is at least 1 cm in length. Subsequently, histopath ologic findings were correlated with macroscopic and clinical findings. Results.-Obliterative muscularization of the submucosa was present in 14 sp ecimens, and in 11 of these 14 it was topographically restricted to strictu res. Submucosal fibrosis was observed in sections from adjacent regions. Ob literative muscularization of the submucosa, including thick-walled vessels and hyperplastic nerves but not prominent scarring, was more common in spe cimens with strictures; the difference was statistically significant (P < . 001). Conclusions.-Obliterative muscularization of the submucosa may be pathogene tically involved in the formation of strictures either directly by causing a sustained spasm, or indirectly by minimizing the vasoprotective role of t he submucosa, impairing repair and enhancing scarring.