A 25 year old man presents to the emergency room with severe abdominal pain. Guaiac test on stool demonstrates occult blood. The patient is taken to exploratory laparotomy, at which a small area of infarcted small bowel is found and surgically removed. Histologic studies on the removed section of bowel demonstrate a recent thrombus occluding a small muscular aery. The adjacent vessel wall shows fibrinoid necrosis with a mixed inflammatory infiltrate containing neutrophils, eosinophils, and mononuclear cells. Which of the following is the most likely cause of the small bowel infarction?
A 25 year old man presents to the emergency room with severe abdominal pain. Guaiac test on stool demonstrates occult blood. The patient is taken to exploratory laparotomy, at which a small area of infarcted small bowel is found and surgically removed. Histologic studies on the removed section of bowel demonstrate a recent thrombus occluding a small muscular aery. The adjacent vessel wall shows fibrinoid necrosis with a mixed inflammatory infiltrate containing neutrophils, eosinophils, and mononuclear cells. Which of the following is the most likely cause of the small bowel infarction?
💡 Explanation
## Core Concept
The question tests the understanding of vasculitis and its effects on blood vessels, particularly in the context of a small bowel infarction. Vasculitis refers to inflammation of the blood vessel walls, which can lead to vessel occlusion, tissue ischemia, and infarction. The presence of fibrinoid necrosis and a mixed inflammatory infiltrate in the vessel wall is characteristic of a specific type of vasculitis.
## Why the Correct Answer is Right
The correct answer, **C. Polyarteritis nodosa (PAN)**, is a type of vasculitis that affects medium and small-sized muscular arteries. The histological findings described - recent thrombus occluding a small muscular artery, fibrinoid necrosis, and a mixed inflammatory infiltrate containing neutrophils, eosinophils, and mononuclear cells - are classic for PAN. PAN can lead to ischemia and infarction of the affected organ, in this case, the small bowel.
## Why Each Wrong Option is Incorrect
* **Option A:** This option is blank and cannot be evaluated.
* **Option B:** This option is blank and cannot be evaluated.
* **Option D:** This option is blank and cannot be evaluated.
However, common differentials for vasculitis and small bowel infarction include:
* **Option A** could potentially represent another form of vasculitis or a different cause of small bowel infarction, but without specific details, it's hard to assess its accuracy.
* **Option B** similarly lacks specificity but could represent conditions like thrombosis due to atherosclerosis or embolic events.
* **Option D** might represent other types of vasculitis, such as **Giant Cell Arteritis** or **Microscopic Polyangiitis**, which have different clinical and histological features.
## Clinical Pearl / High-Yield Fact
A key point to remember is that **Polyarteritis Nodosa (PAN)** is a medium and small vessel vasculitis that does not typically involve the arterioles, capillaries, or venules, and it is not associated with glomerulonephritis or pulmonary capillaritis, distinguishing it from other forms of vasculitis like **Microscopic Polyangiitis** and **Granulomatosis with Polyangiitis**.
## Correct Answer: C. Polyarteritis nodosa.
✓ Correct Answer: D. Polyaeritis nodosa
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