A 5-year-old boy has had diarrhea for a week, averaging six low volume stools per day, which appear mucoid and sometimes blood-tinged. On physical examination, his temperature is 37.4deg C. He has mild lower abdominal tenderness, but no masses. A stool culture is positive for Shigella sonnei. Which of the following microscopic findings would most likely be seen in this child’s colon?

**Core Concept**
The child's symptoms are consistent with a bacterial infection of the colon, specifically Shigella sonnei, a common cause of dysentery in children. The pathogenesis involves invasion of the colonic epithelium by the bacteria, leading to inflammation and damage to the mucosa.

**Why the Correct Answer is Right**
Shigella sonnei causes a self-limiting bacterial dysentery characterized by inflammation of the colon (colitis). The bacteria invade the colonic epithelial cells, leading to an intense inflammatory response, which results in the production of pus and blood in the stool. The presence of blood and mucus in the stool is a hallmark of Shigella infection. The inflammation also leads to ulceration of the colonic mucosa, which would be visible on microscopic examination.

**Why Each Wrong Option is Incorrect**
* **Option A:** This would be more consistent with a viral or chemical colitis, which typically does not cause significant inflammation or ulceration of the colonic mucosa.
* **Option B:** This is not specific for Shigella infection and could be seen in a variety of conditions, including inflammatory bowel disease or ischemic colitis.
* **Option C:** This would be more consistent with a condition such as Crohn's disease or ulcerative colitis, which involves chronic inflammation and ulceration of the colon.

**Clinical Pearl / High-Yield Fact**
Shigella sonnei is a common cause of bacterial dysentery in children, and the presence of blood and mucus in the stool is a key diagnostic clue. It is essential to consider Shigella in the differential diagnosis of children with diarrhea and bloody stools.

**Correct Answer:** C. Ulceration of the colonic mucosa.

✓ Correct Answer: A. Epithelial disruption with overlying neutrophilic exudate