182 Gut and Liver, Vol. 5, No. 2, June 2011 of the Intestinal Disease (KASID) designed of research on fre- quency of microscopic colitis and clinical pattern of the patient with chronic diarrhea in Korea through the prospective multi- center study. MATERIALS AND METHODS 1. Subjects It was a manifold collaboration research from March 2008 to February 2009 with the adults over 15 years old with chronic diarrhea. Chronic diarrhea is defined as watery diarrhea more than 3 times a day at least for 4 weeks. However, those cases showing inflammation in colonic mucosa such as inflammatory bowel disease and abnormal stool exam showing steatorrhea and parasite infection were excluded in the research. 2. Methods Two mucosal biopsies were taken from every segment of the colon (cecum, ascending colon, transverse colon, descending colon, and sigmoid colon) and from the rectum. The histologi- cal features of microscopic colitis are chronic inflammatory cells infiltrating the lamina propria of mucosa, increase of in- traepithelial lymphocyte (IEL) and epithelial damage, such as flattening and detachment. The number of IEL is more than 20 in 100 epithelial cells in lymphocytic colitis (LC) (Fig. 1A). The thickness of subepithelial collagen layer is more than 10 μm in collagenous colitis (CC) (Fig. 1B and C). Also we divided into Fig. 1. Pathologic finding of microscopic colitis. (A) Lymphocytic colitis (H&E stain, ×400). Note the intraepithelial lymphocytosis and mixed inflammatory infiltrate in the lamina propria, as well as the surface epithelial damage. In distinction from ulcerative colitis or Crohn’s colitis, the crypt architecture is normal. (B) Collagenous colitis (H&E stain, ×200). (C) Collagenous colitis (Masson’s trichrome stain, ×400). In addition to the inflammatory infiltrate, note the thickened subepithelial collagen band. Fig. 2. Diagnostic rate of microscopic colitis. LC, lymphocytic colitis; CC, collagenous colitis. two subgrouped, if the case shows the number of lymphocyte is 10 to 20 in 100 epithelial cells diagnosed as suspicious LC and the thickness of the collagen layer is 5 to 10 μm diagnosed as suspicious CC. 3. Statistical analysis Independent t-test was used for ages, the number of diar- rhea and the period between microscopic colitis (MC) group