USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What histological findings are associated with Renal Artery Stenosis?

1. Intimal fibroplasia

2. Presence of internal elastic lamina in dilated areas

3. Medial fibroplasia

4. Presence of prominent smooth muscle cells

The correct answer is: Medial fibroplasia

Renal artery stenosis often presents with histological findings that include medial fibroplasia. This condition typically involves a focal proliferation of smooth muscle cells and extracellular matrix within the medial layer of the arterial wall, which leads to the narrowing of the artery. This is particularly common in cases of renal artery stenosis due to fibromuscular dysplasia, leading to a characteristic 'string of beads' appearance on imaging. While intimal fibroplasia can occur in other vascular conditions, it is less specifically associated with renal artery stenosis than medial fibroplasia. The presence of the internal elastic lamina in dilated areas can indicate changes related to arterial remodeling, but it does not directly relate to the pathology of renal artery stenosis itself. Similarly, the presence of prominent smooth muscle cells can be seen in various vascular diseases and does not specifically indicate the stenosis associated with renal arteries. Medial fibroplasia, however, is a hallmark finding in this condition, making it the most relevant histological association.