Question

Normal-sized to enlarged kidneys in a patient with chronic renal failure is indicative of

• A. Benign nephrosclerosis
• B. Chronic glomerulonephritis
• C. Chronic interstitial nephritis
• D. Primary amyloidosis

Hint:

Think of a disease that deposits material inside the kidney rather than scarring it down.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks which cause of chronic renal failure keeps the kidneys normal in size or even enlarges them, when most causes of chronic renal failure classically shrink the kidneys.

Step 2: Key Concept or Approach:
Chronically failing kidneys usually undergo progressive scarring and shrink over time. A small subset of diseases instead infiltrate or deposit material within the kidney, which can preserve or increase kidney size even as function declines, and recognising this exception helps narrow the differential when imaging shows normal-to-large kidneys despite renal failure.

Step 3: Working Through the Options:
Benign nephrosclerosis, from long-standing hypertension, causes gradual ischaemic scarring and shrinkage of both kidneys. Chronic glomerulonephritis leads to progressive glomerular scarring with contracted, often granular, small kidneys. Chronic interstitial nephritis similarly produces tubulointerstitial scarring with small, irregularly scarred kidneys over time. Primary amyloidosis, however, is an infiltrative disease; amyloid protein deposits expand the renal interstitium and glomeruli, which can keep the kidneys normal-sized or actually enlarged even as renal failure progresses, in the same way diabetic nephropathy, HIV nephropathy, and polycystic kidney disease behave.

Step 4: Conclusion:
The correct answer is primary amyloidosis, since deposition of amyloid within the kidney preserves or increases its size despite chronic renal failure.