The colonoscopy is normal but histology of the mucosal biopsy reveals an accumulation of lymphocytes in the colonic epithelium and connective tissue (lamina propria). Collagenous colitis shares this feature but additionally shows a distinctive thickening of the subepithelial collagen table.
Lymphocytic colitis
Collagenous colitis
Microscopic colitis
Cytomegalovirus colitis
Diversion colitis
Chemical colitis
Ulcerative colitis
Strongyloidiasis