Final answer:
Acute renal failure after starting an ACE inhibitor for hypertension is most commonly associated with renal artery stenosis, as this condition can be worsened by the medication's impact on renal hemodynamics.
Step-by-step explanation:
The acute renal failure after starting an ACE inhibitor for hypertension (HTN) can be caused by various conditions that lead to compromised renal function. Among the options provided:
- Henoch-Schonlein purpura
- Wegener granulomatosis
- Microscopic polyangiitis
- Renal artery stenosis
The most likely cause of acute renal failure in the context of initiating ACE inhibitor therapy is renal artery stenosis. This is because ACE inhibitors can decrease glomerular filtration rate (GFR) by reducing the constriction of efferent arterioles, which is particularly hazardous in the presence of existing renal artery stenosis. In cases where renal blood flow is already compromised, the use of ACE inhibitors can exacerbate renal ischemia, potentially leading to acute renal failure.