A 62-year-old woman is admitted to the emergency department with abdominal pains of uncertain origin. A CT scan reveals an aortic aneurysm affecting the origin of the superior mesenteric artery, resulting in ischemia to an abdominal organ. Which of the following organs is most likely affected?

**Core Concept**
The superior mesenteric artery (SMA) supplies blood to the midgut, a region of the gastrointestinal tract that includes the duodenum, jejunum, ileum, and a portion of the ascending colon. An aneurysm affecting the origin of the SMA can lead to ischemia in this region.

**Why the Correct Answer is Right**
The SMA arises from the abdominal aorta, just below the celiac trunk, and supplies blood to the midgut. An aneurysm at this location can lead to thrombosis or embolism of the SMA, resulting in ischemia to the organs supplied by this artery. The most likely affected organ is the duodenum, which is a part of the midgut and has a high risk of ischemia due to its proximity to the SMA origin. The duodenum is also a common site for SMA syndrome, a condition characterized by chronic mesenteric ischemia due to SMA stenosis or occlusion.

**Why Each Wrong Option is Incorrect**
**Option A:** The ascending colon is primarily supplied by the right colic artery, which branches off from the superior mesenteric artery but is not the most likely affected organ in this scenario.
**Option B:** The stomach is primarily supplied by the celiac trunk, which is a separate arterial trunk that arises from the abdominal aorta above the SMA origin.
**Option C:** The spleen is primarily supplied by the splenic artery, which branches off from the celiac trunk and is not directly affected by an aneurysm at the SMA origin.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the SMA syndrome, which can present with chronic abdominal pain, weight loss, and malabsorption. A high index of suspicion is required for early diagnosis and treatment to prevent complications such as bowel infarction.

**Correct Answer:** C. The duodenum.

✓ Correct Answer: A. Ileum