Recognition of Microscopic Colitis at Colonoscopy

Abstract

Microscopic colitis is a common condition in Canada and is characterized by watery diarrhea with normal endoscopic mucosal appearance using conventional white-light endoscopy. Two types of microscopic colitis are recognized by histological appearance: lymphocytic colitis and collagenous colitis. Recent studies suggest that 10% to 30% of older patients who present with diarrhea and demonstrate normal mucosal appearance at endoscopy have microscopic colitis (1). Increasingly, however, with high-definition endoscopy assisted by postprocessing of images by filter techniques in combination with chromoendoscopy, subtle abnormalities of the mucosa are apparent in patients with microscopic colitis. iScan (Pentax, Japan) is a newly developed postprocessing light filter that enhances details of the mucosal surface, mucosal patterns (i-Scan p designated iScan 1) and vessel architecture (i-Scan v designated iScan 2). i-Scan is a technique designed for differentiating neoplastic from non-neoplastic lesions in the colon. This new digital modality can characterize mucosal patterns of the gastrointestinal mucosa in detail. Subtle abnormalities can, therefore, be recognized as either neoplastic or inflammatory. Hoffman et al (2) have tested the efficacy of high-definition endoscopy alone in comparison with i-Scan or chromoendoscopy with methylene blue (0.1%) in screening for colorectal cancer. They demonstrated that both i-Scan and chromoendoscopy identified more lesions compared with high-definition endoscopy alone. i-Scan was also able to predict neoplasia as precisely as chromoendoscopy, with an accuracy of 89% to 97%. Case Presentation A 50-year-old woman with persistent undiagnosed chronic watery diarrhea underwent colonoscopy, with random biopsies that were negative. Another colonoscopy was performed with iScan + chromoendoscopy with 0.2% indigo carmine to enhance mucosal surfaces and patterns, and to target biopsies in the colon. iScan 1 and iScan 2 showed irregularity of the colonic mucosal pattern, although the mucosa appeared normal with white-light endoscopy. iScan + chromoendoscopy with indigo carmine characterized, in detail, the mucosal pattern as nodularmosaic with a small honeycomb pit-pattern appearance (Figure 1). Such an appearance is characteristic of microscopic colitis. Targeted