Renovascular Hypertension (Answer: D)
Renovascular hypertension typically does NOT present with enlarged kidneys; in fact, kidneys in renovascular disease are usually normal-sized or may show unilateral atrophy in severe cases.
Kidney Size in Chronic Renal Failure: Key Distinctions
The critical concept here is understanding which conditions cause kidney enlargement versus those that cause normal or small kidneys:
Conditions That Present With Enlarged Kidneys:
Polycystic Kidney Disease (A): Characterized by progressive development of multiple fluid-filled cysts causing marked bilateral kidney enlargement 1, 2. This is the most common inherited kidney disease and kidneys can become massively enlarged.
Obstructive Nephropathy (B): Acute or chronic obstruction causes hydronephrosis with kidney enlargement. Ultrasound shows >90% sensitivity for detecting hydronephrosis and bladder distension 3.
Diabetic Glomerulosclerosis (C): In early diabetic nephropathy, kidneys are typically normal-sized or even enlarged due to hyperfiltration and glomerular hypertrophy. Small kidneys only develop in advanced end-stage disease 4.
Multiple Myeloma (E): Can present with enlarged kidneys due to light chain deposition, tubular obstruction from cast formation, and infiltrative processes 5, 6. The kidneys may show normal or increased size, particularly in acute presentations.
The Exception - Renovascular Hypertension:
Renovascular hypertension results from renal artery stenosis (90% atherosclerotic, 10% fibromuscular dysplasia) causing decreased renal perfusion 7, 8. The pathophysiology involves:
- Reduced blood flow activating the renin-angiotensin-aldosterone system
- Progressive ischemic changes without cyst formation or infiltration
- Potential for unilateral kidney atrophy in severe stenosis
- Kidneys remain normal-sized or become atrophic, NOT enlarged 9, 10
Clinical Pearls:
The ACR Appropriateness Criteria emphasize that imaging in renovascular hypertension focuses on detecting arterial stenosis, not kidney enlargement 7. Duplex ultrasound, the primary screening tool, assesses renal artery velocities and resistive indices—not kidney size as a diagnostic feature 3.
Common pitfall: Don't confuse the hypertension caused by renovascular disease with the kidney size. While the blood pressure is severely elevated, the kidneys themselves are ischemic and shrinking, not enlarging.