A 26-year-old man has had intermittent cramping abdominal pain and low-volume diarrhea for 3 weeks. On physical examination, he is afebrile; there is mild lower abdominal tenderness but no masses and bowel sounds are present. A stool sample is positive for occult blood. The symptoms subside within 1 week. Six months later, abdominal pain recurs with perianal pain. On physical examination, there is now a perirectal fistula. Colonoscopy shows many areas of mucosal edema and ulceration and some areas that appear normal. Microscopic examination of a biopsy specimen from an ulcerated area shows a patchy acute and chronic inflammatory infiltrate crypt abscesses, and noncaseating granulomas. Which of the following underlying disease processes best explains these findings?
A 26-year-old man has had intermittent cramping abdominal pain and low-volume diarrhea for 3 weeks. On physical examination, he is afebrile; there is mild lower abdominal tenderness but no masses and bowel sounds are present. A stool sample is positive for occult blood. The symptoms subside within 1 week. Six months later, abdominal pain recurs with perianal pain. On physical examination, there is now a perirectal fistula. Colonoscopy shows many areas of mucosal edema and ulceration and some areas that appear normal. Microscopic examination of a biopsy specimen from an ulcerated area shows a patchy acute and chronic inflammatory infiltrate crypt abscesses, and noncaseating granulomas. Which of the following underlying disease processes best explains these findings?
💡 Explanation
**Core Concept**
The patient's symptoms, colonoscopy findings, and biopsy results are consistent with a chronic inflammatory bowel disease (IBD) characterized by recurring episodes of intestinal inflammation, mucosal ulceration, and granuloma formation. This condition is distinct from infectious or ischemic causes of colitis.
**Why the Correct Answer is Right**
The presence of noncaseating granulomas, mucosal edema, ulceration, and crypt abscesses in the biopsy specimen, along with the clinical presentation of recurrent abdominal pain and perianal fistula, is diagnostic of Crohn's disease (CD). This condition is a type of IBD that can affect any part of the gastrointestinal tract, from the mouth to the anus, but commonly affects the terminal ileum and colon. The chronic inflammatory infiltrate and granuloma formation are hallmarks of CD, which distinguishes it from other forms of IBD, such as ulcerative colitis (UC).
**Why Each Wrong Option is Incorrect**
* **Option A:** Ulcerative colitis (UC) typically presents with continuous inflammation of the colonic mucosa, starting from the rectum and extending proximally. The presence of noncaseating granulomas and perianal fistulae is less common in UC.
* **Option B:** Irritable bowel syndrome (IBS) is a functional disorder characterized by chronic abdominal pain, changes in bowel habits, and bloating, but it does not involve inflammation or granuloma formation.
* **Option D:** Infections, such as amoebiasis or shigellosis, can cause colitis with fever, bloody diarrhea, and abdominal pain, but the microscopic findings and clinical course of this patient do not suggest an infectious etiology.
**Clinical Pearl / High-Yield Fact**
Crohn's disease can affect any part of the gastrointestinal tract, but it commonly involves the terminal ileum and colon. The presence of noncaseating granulomas in the biopsy specimen is a key diagnostic feature of CD.
**Correct Answer:** C. Crohn's disease.
✓ Correct Answer: B. Crohn disease
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