PRESENT STATUS AND ENDOSCOPIC DIAGNOSIS OF DRUG-ASSOCIATED COLLAGENOUS COLITIS

<p>Collagenous colitis (CC) is a disorder characterized by non-bloody chronic diarrhea and thickening of the subepithelial collagen band, and it is usually diagnosed by histological examination of biopsy specimens. CC and lymphocytic colitis (LC) are two subtypes of microscopic colitis (MC). In Western nations, the incidence of LC is slightly higher than that of CC. The incidence of MC increased during the 1980ʼs and 1990ʼs; however, it has become stable thereafter. Although the etiology of MC is not yet evident, it is considered to be a multifactorial disorder. Use of a nonsteroidal anti-inflammatory drug (NSAID) and/or proton pump inhibitor (PPI) has been shown to increase the risk of developing CC by case-control studies, and recently the role of PPIs has attracted attention.</p><p>In Japan, reported cases of CC increased after 2000, although the frequency is far less than that in Western nations. Most of the CC cases are associated with the use of PPI (especially lansoprazole) or NSAID. Furthermore, there are very few reported cases of LC in Japan. Concerning MC, many discrepancies exist between nations.</p><p>Originally, the endoscopic findings of patients with CC have been described as normal; however, endoscopic abnormalities have been reported to be common. Endoscopic findings of patients with CC are summarized as follows: 1) Changes in color: erythema, red spots, discoloration, etc. 2) Changes in vascular pattern: diminished vascular pattern, crowded vascular pattern, etc. 3) Changes in surface property: edema, friability, rough surface, granular surface, pseudomembranes, mucosal tears (linear ulcers/scars, “cat scratch”, crack-like grooves, etc.). 4) Other findings: loss of haustration.</p><p>In drug-associated CC cases, discontinuation of the suspected drug is usually followed by recovery from diarrhea. Our understanding of the pathophysiology of MC is still not satisfactory. The cause of the heterogeneity of MC is expected to be elucidated.</p>