**Core Concept**
In acute diverticulitis, the sigmoidoscopic finding is characterized by inflammation and infection of the diverticula in the sigmoid colon. This condition is often caused by a bacterial overgrowth in the diverticula, leading to an inflammatory response.

**Why the Correct Answer is Right**
The correct answer is related to the presence of diverticula, which are small, bulging pouches in the wall of the sigmoid colon. In acute diverticulitis, these diverticula become inflamed and infected, leading to symptoms such as abdominal pain, fever, and changes in bowel habits. The inflammation and infection cause the diverticula to become tender and swollen, which can be visualized during sigmoidoscopy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe a finding that is characteristic of acute diverticulitis. Diverticula are a normal finding in many people, but they do not necessarily indicate acute diverticulitis.

**Option B:** This option is incorrect because it describes a finding that is more typical of inflammatory bowel disease, such as Crohn's disease or ulcerative colitis. In these conditions, the colon is inflamed and may have ulcers or bleeding.

**Option C:** This option is incorrect because it describes a finding that is more typical of a colonic polyp. Polyps are growths on the surface of the colon that can be benign or malignant.

**Clinical Pearl / High-Yield Fact**
In patients with acute diverticulitis, it is essential to rule out other causes of abdominal pain, such as appendicitis or inflammatory bowel disease, through a combination of clinical evaluation, laboratory tests, and imaging studies.

**Correct Answer: D.**