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Difficulty: MediumNephrology

Match each classic urinalysis sediment finding with its most likely associated renal pathology.

  • Muddy brown granular casts and renal tubular epithelial cellsAcute tubular necrosis
  • Dysmorphic red blood cells and red blood cell (RBC) castsAcute glomerulonephritis
  • White blood cell (WBC) casts, sterile pyuria, and urinary eosinophilsAcute interstitial nephritis
  • Oval fat bodies and fatty casts with a 'Maltese cross' appearance under polarized lightNephrotic syndrome
  • Broad, waxy casts with varying degrees of proteinuriaAdvanced chronic kidney disease

Answer

Muddy brown granular casts match with Acute tubular necrosis. Dysmorphic red blood cells and RBC casts match with Acute glomerulonephritis. White blood cell casts and urinary eosinophils match with Acute interstitial nephritis. Oval fat bodies match with Nephrotic syndrome. Broad, waxy casts match with Advanced chronic kidney disease.
Each urinalysis finding is highly specific to a particular pathophysiologic state in the kidney. Recognizing these classic sediment patterns allows for rapid differentiation between prerenal, intrinsic, and postrenal causes of kidney injury, as well as distinguishing between nephritic and nephrotic syndromes.

Step-by-Step Solution

1
Evaluate the finding of muddy brown granular casts.
Matches with acute tubular necrosis.
These casts represent desquamated, necrotic tubular epithelial cells seen in ischemic or toxic renal injury.
2
Evaluate the finding of dysmorphic red blood cells and RBC casts.
Matches with acute glomerulonephritis.
Glomerular damage allows RBCs to pass into the tubules, where they become deformed (dysmorphic) and trapped in Tamm-Horsfall mucoprotein (casts).
3
Evaluate the finding of WBC casts and urinary eosinophils.
Matches with acute interstitial nephritis.
Interstitial inflammation, often drug-induced, leads to WBC exudation and cast formation in the tubules.
4
Evaluate the finding of oval fat bodies and a 'Maltese cross' appearance.
Matches with nephrotic syndrome.
Severe proteinuria is accompanied by lipiduria; macrophages engulf lipids to form oval fat bodies which exhibit the Maltese cross sign under polarized light.
5
Evaluate the finding of broad, waxy casts.
Matches with advanced chronic kidney disease.
These casts form in dilated tubules that have undergone compensatory hypertrophy due to significant loss of functioning nephrons.

Key Concept

Interpretation of urinalysis sediment is crucial for differentiating the underlying etiology of acute and chronic kidney diseases.
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Topics

Nephrology

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