Collagenous colitis (CC) is a well-known cause of chronic non-bloody diarrhea, especially in elderly women. CC is characterized histopathologically by an increase in the thickness of the subepithelial collagen layer to at least 10 mum, epithelial damage, and chronic inflammation of the lamina propria. Generally, the colonic mucosa in CC is macroscopically normal, although minor, non-specific abnormalities may be found. Due to the recent advancement of endoscopic and diagnostic technologies, however, microscopic mucosal abnormalities and specific longitudinal linear lacerations of the mucosa characteristic of CC have been identified. The association of CC with non-steroidal anti-inflammatory drugs and proton pump inhibitors has also been reported. Since definitive diagnosis of CC has to rely on pathologically documented collagen bands and mononuclear infiltration, the efficiency and precision of colonic biopsy need to be improved. Of the 29 CC patients that we have encountered at our institution, it was in 15 of 29 cases that the endoscopic finding that we performed a biopsy on was apparent. Our comparison of the endoscopic and histopathological findings of CC in the 15 patients showed that the mucosa frequently appeared coarse and nodular on the surface of the mucosa, which was also significantly thicker in collagen bands, demonstrating a strong correlation between collagen band formation and CC. Also, the coarse and nodular surface of the mucosa was most frequently seen affecting the proximal colon. The results suggest that endoscopic observation and biopsy of the proximal colon, where a coarse and nodular surface of the mucosa is often found, may be useful for confirmation of the diagnosis in patients with suspected CC.
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