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Collagenous colitis (CC) is widely recognised as a cause of chronic diarrhoea. CC is sometimes diagnosed with cat scratch sign found during colonoscopy.1 On the other hand, no abnormality is observed in more than 80% of cases; hence, the diagnosis of CC cannot be made without biopsy. We report a case of a patient with mucosal tears occurring during colonic endoscopy, who was successfully diagnosed with CC by histopathological analysis.
A 70-year-old man who had been taking lansoprazole for gastro-oesophageal reflux disease visited our outpatient department, complaining of chronic watery diarrhoea that had lasted for more than a month. Colonoscopy was performed to diagnose the cause of symptoms. Although the colonic mucosa appeared normal, several longitudinal mucosal tears suddenly occurred in the left colon (figure 1). The patient had no abdominal symptoms. The mucosal tears were speculated to be cat scratch sign. Biopsies of these lesions revealed chronic inflammation in the lamina propria on staining with haematoxylin-eosin and thickening of the subepithelial collagen bands on staining with Masson’s trichrome (figure 2). The patient was therefore diagnosed with CC.
CC occurs due to the ingestion of drugs such as proton pump inhibitors and non-steroidal anti-inflammatory drugs; also its prevalence is increasing.2 3 CC, in this case, was considered to be triggered by lansoprazole and the mucosal tears by the intestinal pressure increase due to air supply during colonoscopy. Procedure-related perforation was reported in CC; so cautious air insufflation is necessary.4 In terms of location, both right and left biopsies were frequently positive in CC.5 The patient’s symptoms of diarrhoea resolved soon after he discontinued lansoprazole.
Cautious air insufflation at a time of colonoscopy is necessary in patients with macroscopic findings and suspected CC.
We experienced mucosal tears occurring just during colonic endoscopy.
Mucosal tears are findings that lead to endoscopic diagnosis of collagenous colitis.
For patients with macroscopic findings at the time of colonoscopy, there is slightly increased risk of colonic perforation.
Contributors YS performed the colonic endoscopy. YS and KF managed the patient and wrote this article.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Obtained.