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Question

Difficulty: MediumNephrology

Match each characteristic urinalysis sediment finding with its most likely underlying renal pathology.

  • Pigmented 'muddy brown' granular casts and epithelial cell castsAcute tubular necrosis
  • Dysmorphic red blood cells and red blood cell castsAcute glomerulonephritis
  • White blood cell casts, sterile pyuria, and eosinophiluriaAcute interstitial nephritis
  • Fatty casts and oval fat bodies with a 'Maltese cross' appearance under polarized lightNephrotic syndrome

Answer

The correct pairings link muddy brown casts to acute tubular necrosis, dysmorphic red blood cells to acute glomerulonephritis, white blood cell casts with eosinophiluria to acute interstitial nephritis, and fatty casts to nephrotic syndrome.
Each urinalysis sediment pattern reflects a distinct pathophysiological process in the kidney. Granular casts form from necrotic tubular cells (ATN). RBC casts form from glomerular bleeding (nephritic syndrome). WBC casts with eosinophils reflect interstitial allergic inflammation (AIN). Fatty casts reflect severe hyperlipidemia and lipiduria secondary to profound proteinuria (nephrotic syndrome).

Step-by-Step Solution

1
Analyze the urinalysis finding of 'muddy brown' granular casts.
Matches with Acute tubular necrosis.
These casts are formed from necrotic tubular epithelial cells sloughing into the tubular lumen due to ischemic or toxic injury.
2
Analyze the finding of dysmorphic red blood cells and red blood cell casts.
Matches with Acute glomerulonephritis.
Dysmorphic RBCs and casts signify bleeding of glomerular origin, which occurs when inflammation disrupts the glomerular basement membrane.
3
Analyze the finding of white blood cell casts, sterile pyuria, and eosinophiluria.
Matches with Acute interstitial nephritis.
WBC casts indicate inflammation in the kidney itself (unlike simple cystitis), and eosinophils strongly suggest an allergic hypersensitivity reaction in the interstitium.
4
Analyze the finding of fatty casts and oval fat bodies.
Matches with Nephrotic syndrome.
Significant lipiduria occurs alongside massive proteinuria due to altered glomerular permeability and compensatory hepatic lipid synthesis.

Key Concept

Correlation of urinalysis sediment findings with specific renal pathologies
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Topics

Nephrology

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