A 53-year-old woman complains of acute diarrhea and severe abdominal pain. She was recently treated with broad-spectrum antibiotics for community-acquired pneumonia. A CBC shows a WBC count of 24,000/mL. The patient subsequently develops septic shock and dies. A portion of her colon is shown at autopsy. These findings are typical of which of the following gastrointestinal diseases?

**Core Concept**
The underlying principle being tested involves the relationship between broad-spectrum antibiotic use, disruption of normal gut flora, and the subsequent overgrowth of pathogenic bacteria. This scenario often leads to a specific, severe gastrointestinal condition. The key concept here is **antibiotic-associated diarrhea** and its potential complications, including the overgrowth of **Clostridioides difficile**.

**Why the Correct Answer is Right**
The correct answer is related to the overgrowth of **Clostridioides difficile**, a bacterium that can cause severe diarrhea and life-threatening colitis, particularly after the use of broad-spectrum antibiotics that disrupt the normal intestinal flora. The patient's recent antibiotic treatment for pneumonia, followed by acute diarrhea, abdominal pain, and a high WBC count, suggests a severe infection. The development of septic shock and the findings at autopsy are consistent with **pseudomembranous colitis**, a condition characterized by the formation of pseudomembranes in the colon due to **C. difficile** overgrowth.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because, while it may involve gastrointestinal symptoms, it does not directly relate to the overgrowth of a specific pathogen following antibiotic use.
**Option B:** This option is incorrect as it does not typically present with the severe, life-threatening complications seen in this patient.
**Option C:** This choice is incorrect because, although it involves the gastrointestinal tract, it does not specifically relate to the consequences of antibiotic-induced disruption of normal flora.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **broad-spectrum antibiotic use** can lead to **C. difficile** overgrowth, resulting in severe diarrhea and potentially life-threatening complications like pseudomembranous colitis. Early recognition and treatment are crucial to prevent severe outcomes.

**Correct Answer:** D. Pseudomembranous colitis.

✓ Correct Answer: D. Pseudomembranous colitis