What is the most common area of the colon involved in ischemic colitis?

Ischemic colitis is most commonly associated with areas of the colon that have the most tenuous blood supply, particularly the left colon. This region includes the descending colon and sigmoid colon, which are more likely to experience ischemia due to the more distal nature of their blood supply compared to other regions of the colon. The superior mesenteric artery primarily supplies the right colon and a substantial part of the transverse colon, while the blood supply to the left colon mainly comes from the inferior mesenteric artery, making it more susceptible to ischemic conditions, especially when there are systemic or localized factors like low blood volume or vascular occlusion.

The right colon, while it can be involved in ischemic conditions, is generally better perfused due to its direct supply from the superior mesenteric artery. The transverse colon's involvement is also less common because it receives blood from both the superior and inferior mesenteric arteries, providing alternative pathways for blood flow. The rectum is similarly less commonly affected since it is generally well-perfused due to its dual supply from both the inferior mesenteric artery and the internal pudendal arteries.

Understanding these vascular supply differences clarifies why the left colon is the most commonly affected area in cases of ischemic col