Upto 20% of patients with chronic diarrhea with a normal endoscopy will have a microscopic colitis.[1]
↑Datta, I.; Brar, SS.; Andrews, CN.; Dupre, M.; Ball, CG.; Buie, WD.; Beck, PL. (Oct 2009). "Microscopic colitis: a review for the surgical endoscopist.". Can J Surg52 (5): E167-72. PMID19865548.