A 70-year-old patient presents with sudden onset abdominal pain and bloody diarrhea. The attending physician suspects ischemic colitis and decides to perform imaging studies and possibly a colonoscopy to confirm the diagnosis and identify the affected area.
Which of the following is the most common site of ischemic colitis?
A. Splenic flexure
B. Transverse colon
C.Hepatic flexure
D. ileocaecal junction
Correct Answer: A. Splenic flexure
Explanation:
Ischemic colitis occurs when there is a reduction in blood flow to a part of the colon, leading to inflammation and injury of the colon wall. The splenic flexure is the most common site for ischemic colitis due to its unique blood supply. Here’s why:
1. Splenic Flexure (A):
– The splenic flexure, located at the junction of the transverse and descending colon, is a watershed area with a dual blood supply from the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).
– Watershed areas are regions of the colon that receive blood supply from the most distal branches of two major arteries, making them particularly vulnerable to ischemia during episodes of decreased blood flow (e.g., hypotension, arterial blockage).
2. Transverse Colon (B):
– The transverse colon receives its blood supply primarily from the middle colic artery, a branch of the SMA.
– While the transverse colon can be affected by ischemia, it is generally not considered a watershed area, making it less vulnerable than the splenic flexure.
– Ischemic colitis in the transverse colon is less common unless there is a generalized or severe reduction in blood flow affecting the SMA territory broadly.
3. Hepatic Flexure (C):
– The hepatic flexure is located at the junction of the ascending and transverse colon, receiving blood from the right colic artery (a branch of the SMA) and sometimes from collateral branches.
– Like the transverse colon, it is not a typical watershed area, making it less prone to ischemic colitis under normal conditions.
– Ischemic colitis in the hepatic flexure can occur but is not as common as in the splenic flexure.
4. Ileocecal Junction (D):
– The ileocecal junction is where the small intestine (ileum) meets the large intestine (cecum).
– It receives its blood supply from the ileocolic artery, a branch of the SMA.
– Ischemic events in this area are relatively rare compared to other regions of the colon. When the ileocecal region is affected by ischemia, it is often part of a broader pattern of ischemia affecting the small intestine or entire right side of the colon.