Macroscopic findings in collagenous colitis: a multi-center, retrospective, observational cohort study.

Background Collagenous colitis (CC) is by definition a histological diagnosis. However, colonoscopy often reveals characteristic endoscopic findings. The aim of this study was to evaluate the frequency and type of endoscopic findings in patients diagnosed with CC in 4 participating centers. Methods This was a retrospective study; the databases of 2 university hospitals in Edinburgh (Scotland) and Malm (Sweden), and 2 district general hospitals in Tomelloso (Spain) and Gateshead (England) were interrogated for patients diagnosed with CC between May 2008 and August 2013. Endoscopy reports and images were retrieved and reviewed; data on lesions, sedation, bowel preparation and endoscopist experience were abstracted. Categorical data are reported as mean +/-SD. Fischer's exact, chi-square and t (unpaired) tests were used to compare datasets. A two-tailed P-value of < 0.05 was considered statistically significant. Results 607 patients (149 male, mean age 66.9 +/-12.25 years) were diagnosed with CC. A total of 108/607 (17.8%) patients had one or more suggestive endoscopy findings: i. e., mucosal erythema/edema, 91/607 (15%); linear colonic mucosal defects, 12/607 (2%); or mucosal scarring, 5/607 (0.82%). For colonic mucosa erythema, there was no difference in the odds of finding erythema with the use of different bowel preparation methods (P= 0.997). For colonic mucosal defects there was some evidence (P= 0.005) that patients colonoscoped by experienced endoscopists had 87% less odds of developing such defects. Moreover, there was evidence that analgesia reduced the odds of developing mucosal defects by 84%. Conclusion A significant minority of patients with CC have endoscopic findings in colonoscopy. The description of such findings appears to be related to the endoscopist's experience.