**Core Concept**
Ischemic colitis occurs when the blood flow to the colon is reduced, leading to tissue damage and potentially life-threatening complications. The condition is most commonly seen in elderly patients with pre-existing vascular disease, and its management often requires prompt recognition and treatment.

**Why the Correct Answer is Right**
The correct answer is the sigmoid colon, which is the most common site of ischemic colitis due to its relatively long length and high oxygen demand. The sigmoid colon receives its blood supply from the sigmoid arteries, which can be more susceptible to atherosclerosis and reduced blood flow. Additionally, the sigmoid colon is more prone to mechanical compression and external pressure, which can further exacerbate ischemia.

**Why Each Wrong Option is Incorrect**
**Option A:** The transverse colon is not as commonly affected by ischemia as the sigmoid colon, although it can still be a site of ischemic colitis, especially in patients with significant vascular disease.

**Option B:** The rectum is less likely to be affected by ischemic colitis, as it receives its blood supply from the superior, middle, and inferior rectal arteries, which are generally more robust than the sigmoid arteries.

**Option C:** The cecum is not a typical site for ischemic colitis, as it receives its blood supply from the ileocolic artery, which is less prone to atherosclerosis and reduced blood flow.

**Clinical Pearl / High-Yield Fact**
Ischemic colitis is often associated with a triad of symptoms: abdominal pain, bloody diarrhea, and fever. Prompt recognition and treatment of ischemic colitis are crucial to prevent complications such as colonic perforation and peritonitis.

**Correct Answer:** C.