Discussion:
Colonic perforation is a rare complication of CC. The leading cause is iatrogenicity, such as colonoscopy, and most of these perforations occur in the right-side colon [5]. Linear ulcerations and deep mucosal tears, observed mainly on the right side of the colon, are considered to be a risk of the perforation [6, 7]. Furthermore, spontaneous perforation in the present case is rare. Mori et al. reported seven cases of spontaneous colonic perforation associated with collagenous colitis [8]. All the patients underwent colon resection and recovered well. Interestingly, these cases and the present case occurred in the descending colon, while spontaneous colon perforation unrelated to collagenous colitis commonly occurs in the sigmoid colon [9]. Therefore, it might be useful to consider the possibility of collagenous colitis if a descending colon perforation of unknown origin is observed.
Watery diarrhea is the main symptom of CC, but almost 10% of patients with CC have no typical symptoms [10]. The present case also had no history of diarrhea. The mechanism of diarrhea is associated with surface injury of the mucosal membrane due to inflammatory mediators in the luminal propria [11]. Although the present did not complain of diarrhea, histopathological examination showed an edematous appearance of the submucosa and a generalized neutrophilic infiltrate. This can lead to spontaneous colonic perforation of the colon.
The criteria for the histological diagnosis of CC are thickened subepithelial collagenous band≧10μm [12]. In the present case, a thickened sub-epithelial band was also found around the perforation site. There were no clinical findings clinical findings indicating diverticulitis, inflammatory bowel disease, or tumors. Furthermore, the present case took PPIs regularly. Therefore, we concluded that CC caused colon perforation in the present case.