Microscopic colitis: a review for the surgical endoscopist.

Microscopic colitis (MC) is an inflammatory condition of the colon distinct from Crohn disease or ulcerative colitis that can cause chronic diarrhea as well as cramping and bloating. Although it was first described 30 years ago, awareness of this entity as a cause of diarrhea has only become more widespread recently. Up to 20% of adults with chronic diarrhea who have an endoscopically normal colonoscopy may have MC. Endoscopic and radiological examinations are usually normal, but histology reveals increased lymphocytes in the colonic mucosa, which typically cause watery nonbloody diarrhea. Treatment is initially supportive but can include corticosteroids and immunomodulatory therapy for resistant cases. Since surgeons perform a large number of colonoscopies and sigmoidoscopies to assess diarrhea, it is important to be aware of this disease and to look for it with mucosal biopsy in appropriate patients.