Investigational treatment options in microscopic colitis.

Collagenous and lymphocytic colitis are the two recognized major presentations of microscopic colitis. Both diseases present with chronic watery diarrhea and a chronic inflammatory infiltrate in the colonic mucosa without specific endoscopic abnormalities, and hence diagnosis is established by histology. Recent epidemiological studies suggest that microscopic colitis may affect as many patients as Crohn's disease or ulcerative colitis. The cause of these diseases is unknown; however, several lines of evidence support the hypothesis of mucosal injury from an unknown agent in the fecal stream. Due to the lack of disease causality, therapeutic management of microscopic colitis is now directed primarily at symptoms' resolution or improvement. Based on current evidence, oral budesonide represents an effective treatment option for patients with microscopic colitis to achieve and maintain remission. Other anti-inflammatory drugs such as mesalazine or bismuth subsalicylate are now under evaluation. The optimal long-term management strategy of microscopic colitis, however, remains an unsolved issue.