The term “ Microscopic colitis” was coined by Read et al¹ to describe a group of patients with chronic diarrhea of undertermined etiology, that exhibited normal macroscopic appearance on colonscopy, but identified to have abnormal features by histologic examination of colonic biopsies. Features of microscopic colitis are divided into two groups: collagenous colitis and lymphocytic colitis, (Figures 1, 2). Clinically both disorders are characterized by chronic watery diarrhea. Some patients will exhibit weight loss, incontinence and vague abdominal pain. However fever, anemia and intestinal bleeding are NOT seen as clinical features of microscopic colitis. Currently, there are no serologic markers for microscopic colitis, but it should be emphasized that serologic antibiody tests for endomysium and/or tissue transglutaminase should be obtained in all cases of microscopic colitis since overlap with celiac disease (10%) has been reported.²

Both lymphocytic and collagenous colitis occur most commonly between the ages of 50 and 70 yrs, with a strong female predominance (especially, collagenous colitis) and frequent association with arthritis, celiac disease and autoimmune disorders. European studies have estimated that microscopic colitis is found in among 9.5 of every 100 patients with chronic watery diarrhea, with collagenous colitis comprising 25% of the cases³. A recent population based cohort study in the United States estimated the incidence for microscopic colitis to be 8.6 cases per 100,000 person years for the period of 1985 to 2001.² Of importance, the researchers identified a significant secular trend with 20 per 100,000 person years identified at the end of the observation period.³

The etiology of “microscopic colitis” remains unknown, but prominent theories include a mucosal inflammatory response triggered by environmental, medication (NSAIDs, lansoprazole), dietary and/or microbial antigens, especially among those with immunologic predisposition^4,5,6,7,8. In the past, treatment of microscopic colitis has been largely empirical. Although, a third of patients respond to anti-diarrhea agents, like loperamide and diphenoxylate with atropine, as well as bulking agents clinical response has not been shown to correlate with histological improvement. Small trials of bismuth subsalicylate (8 chewable tablets per day) and 5-aminosalicylate compounds have shown some clinical and histologic benefit^9,10,11,12. Although budesonide has been shown to be highly effective over a 6-8 week period in several RPCT in collagenous colitis,^13,14 there have been no long term studies evaluating the durability of budesonide efficacy or safety. The study by Miehlke, et al,¹⁵ provides convincing data from a well designed RPCT to indicate that budesonide is both an effective and safe treatment for Collagenous Colitis, with durable efficacy of 75% after 6 months of treatment.

Figure 1	Figure 2

References:

1. Read NW, Krejs GJ, Read MG, et al. Chronic diarrhea of unknown origin. Gastroenterology. 1980;78(2):264-71.1. <Related link>

2. Pardi DS, Loftus EV, Smyrk TC, et al. The epidemiology of microscopic colitis: a population based study in Olmsted County, Minnesota. Gut. 2007;56:504-8. <Related link>

3. Fernández-Bañares F, Esteve M, Salas A, et al. Systematic evaluation of the causes of chronic watery diarrhea with functional characteristics. Am J Gastroenterol. 2007 Nov;102(11):2520-8. <Related link>

4. Bohr J, Tysk C, Eriksson S, Abrahamsson H, Järnerot G. Collagenous colitis: a retrospective study of clinical presentation and treatment in 163 patients. Gut. 1996 Dec;39(6):846-51. <Related link>

5. Thompson RD, Lestina LS, Bensen SP et al. Lansoprazole-associated microscopic colitis: A case series. AM J Gastroenterol 2002;97:2908-13. <Related link>

6. Riddel RH, Tanaka M, Mazzoleni G. Non-steroidal anti-inflammatory drugs as a possible cause of collagenous colitis: A case control study. Gut 1992;33:683-6. <Related link>

7. Anderson T, Anderson JR, Tvede M, Franzmann MB. Collagenous colitis: Are bacterial cytotoxins responsible? AM J Gastroenterol. 1993;88:375-7. <Related link>

8. Ballinger A. Adverse effects of nonsteroidal anti-inflammatory drugs on the colon. Curr Gastroenterol Rep. 2008;10(5):485-9. <Related link>

9. Schiller LR. Diagnosis and management of microscopic colitis syndrome. J Clin Gastroenterol. 2004;38(5 Suppl):S27-30. <Related link>

10. Chatelain D, Mokrani N, Fléjou JF. Microscopic colitis: collagenous colitis and lymphocytic colitis. Ann Pathol. 2007;27(6):448-58. <Related link>

11. Madisch A, Morgner A, Stolte M, Miehlke S. Investigational treatment options in microscopic colitis. Expert Opin Investig Drugs. 2008;17(12):1829-37. <Related link>

12. Chande N, McDonald JW, MacDonald JK. Interventions for treating collagenous colitis. Cochrane Database Syst Rev. 2006 Oct 18;(4):CD003575. <Related link>

13. Baert F, Schmit A, D’Haens G, et al. Budesonide in collagenous colitis: A prospective double-blind, placebo controlled trial with histological follow up. Gastroenterology. 2002;122:20. <Related link>

14. Miehlke S, Heymer P, Bethke B, et al. Budesonide treatment for collagenous colitis: A prospective double-blind, placebo controlled, multicenter study. Gastroenterology. 2002;123:978. <Related link>

15. Miehlke S, Madisch A, Bethke B, Morgner A, et al. Oral budesonide for maintenance treatment of collagenous colitis: A randomized, double-blind, Placebo-Controlled Trial. Gastroenterology. 2008;135:1510-1516. <Related link>