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.