Examkin

Question

Difficulty: EasyNephrology

Match each classic urinalysis sediment finding with the renal pathology it most strongly indicates.

  • Muddy brown granular castsAcute tubular necrosis
  • Red blood cell (RBC) castsAcute glomerulonephritis
  • White blood cell (WBC) castsAcute pyelonephritis
  • Fatty casts and oval fat bodiesNephrotic syndrome

Answer

Muddy brown casts match with acute tubular necrosis; RBC casts with acute glomerulonephritis; WBC casts with acute pyelonephritis; and fatty casts with nephrotic syndrome.
Each specific cellular cast is highly specific to the pathophysiology of the underlying renal disease. RBCs passing through a damaged glomerulus form RBC casts. WBCs entering tubules during infection form WBC casts. Sloughed necrotic cells form muddy brown casts. Heavy lipiduria leads to fatty casts.

Step-by-Step Solution

1
Evaluate the clinical significance of muddy brown granular casts.
Matches with acute tubular necrosis.
These casts are formed by necrotic tubular epithelial cells that slough off into the tubular lumen during ischemic or toxic insults to the kidneys.
2
Evaluate the clinical significance of red blood cell (RBC) casts.
Matches with acute glomerulonephritis.
RBC casts form when red blood cells traverse a damaged glomerular basement membrane and aggregate in the tubules, indicating nephritic conditions.
3
Evaluate the clinical significance of white blood cell (WBC) casts.
Matches with acute pyelonephritis.
WBC casts indicate inflammation in the renal interstitium and tubules, strongly pointing towards pyelonephritis rather than a simple lower urinary tract infection.
4
Evaluate the clinical significance of fatty casts and oval fat bodies.
Matches with nephrotic syndrome.
Severe proteinuria in nephrotic syndrome is accompanied by lipiduria. Macrophages and tubular cells engulf the lipids, forming oval fat bodies.

Key Concept

Specific cellular and acellular casts in urinalysis sediment provide essential diagnostic clues for localizing the mechanism and site of acute or chronic renal injury.
Rate this question

Topics

Nephrology

More questions from this topic