S190 Complete Colonoscopy vs Flexible Sigmoidoscopy to Diagnose Microscopic Colitis

Abstract

Introduction: Microscopic colitis (MC) is a diagnosis made via biopsy, typically requiring a colonoscopy. Current European guidelines recommend performing a colonoscopy as rectal biopsies alone could miss the diagnosis. The purpose of the study is to retrospectively analyze the data on patients diagnosed with MC and determine if complete colonoscopy with right and transverse colon biopsies is needed to make a diagnosis or if flexible sigmoidoscopy with rectal and left sided biopsies would suffice Methods: We performed a retrospective review of data from 1/1/1999 to 1/12/2019 on patients with a pathologic diagnosis of MC at Gundersen Health System. This study was conducted after the approval by the Gundersen Health System institutional review board. We included 342 patients with a histological diagnosis of either collagenous, lymphocytic, or MC. No patients were excluded. We compared the frequencies of left sided versus random colonoscopy biopsy diagnosis of microscopic colitis using Kappa coefficient as a measure of interrater reliability for agreement. A p-value was calculated to evaluate for significant difference. (Table) Results: Out of 342 patients, 129 patients had positive pathologic diagnosis from left sided biopsy sites alone while 184 patients had positive biopsy results from random biopsy sites. This frequency indicates 53.8% of the diagnoses for MC could be missed by performing left sided biopsies alone. The Kappa coefficient of -0.7896 indicates no agreement between obtaining a pathologic diagnosis from left sided biopsy compared to random with a (p < .0001). None of these patients were using budesonide at the time of biopsy. Conclusion: This study highlights agreement with current European guidelines for the recommendation of doing a complete colonoscopy for the diagnosis of MC. Prior studies including Tanaka M, et al. and Offner FA, et al. have shown consistent results with 30 patients but our study included a larger patient population. Having a Kappa coefficient of -0.7896 indicates moderate disagreement between positive biopsy diagnosis from left and random biopsy sites. While this study may not change current guidelines, it adds validity to them and highlights the importance of performing a colonoscopy and not just flexible sigmoidoscopy to diagnose microscopic colitis. Table 1. - Patient Characteristics Patient Characteristics Frequency Collagenous Colitis 113 Lymphocytic Colitis 218 Microscopic Colitis 11 Tubular Adenomas 7