Left-sided ischemic colitis is the most common form of ischemic injury to the gut. Although it is generally considered a condition of elderly persons, it can affect patients of any age. Ischemic colitis is the second or third most common cause of lower gastrointestinal bleeding. The most common medication inducing ischemic colitis is nonsteroidal anti-inflammatory agents. The endoscopic spectrum of ischemic colitis is broad, ranging from mild patchy subepithelial hemorrhage to extensive necrosis. Nevertheless, the 'pathognomonic' endoscopic appearance of ischemic colitis is a 'segmental' involvement of the left colon in the so-called 'watershed area.' This article is part of an expert video encyclopedia. © 2013 Elsevier GmbH.