USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What area is involved in the ischemic area of the colon?

1. Facial angiofibroma

2. Splenic flexure

3. Rectum

4. Giant cell astrocytoma

The correct answer is: Splenic flexure

The splenic flexure, also known as the angle of the colon where the transverse colon transitions into the descending colon, is particularly vulnerable to ischemia due to its blood supply. It is located at the point where the blood supply from the superior mesenteric artery (SMA) and the inferior mesenteric artery (IMA) meets, creating a watershed area. This region is significant because it relies on collateral circulation that can become inadequate during episodes of decreased blood flow. When ischemia occurs, it typically affects areas of the colon that are furthest from adequate blood supply. The splenic flexure is often a prime candidate in conditions such as colonic ischemia or splenic flexure syndrome, particularly due to its positioning and the nature of its arterial supply. Understanding the vascular anatomy and the significance of watershed areas is crucial in diagnosing and managing complications arising from ischemic events in the colon. The other options do not pertain to the ischemic region of the colon in this context. Facial angiofibromas are benign tumors related to connective tissue, the rectum has a more reliable blood supply due to the inferior rectal artery, and giant cell astrocytomas are a type of tumor found in the brain, not related