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Difficulty: MediumNephrology

Match the following classic urinalysis sediment findings with the most appropriate renal pathology or clinical syndrome.

  • Muddy brown granular castsAcute tubular necrosis (ATN)
  • Red blood cell (RBC) castsNephritic syndrome
  • White blood cell (WBC) castsAcute interstitial nephritis or pyelonephritis
  • Fatty casts with 'Maltese cross' appearanceNephrotic syndrome
  • Broad waxy castsChronic kidney disease (CKD)

Answer

Muddy brown granular casts match with acute tubular necrosis; RBC casts match with nephritic syndrome; WBC casts match with acute interstitial nephritis or pyelonephritis; fatty casts match with nephrotic syndrome; and broad waxy casts match with chronic kidney disease.
Each type of urinary cast provides specific clues about the anatomical site and mechanism of renal injury. Muddy brown casts reflect tubular cell death (ATN). RBC casts reflect glomerular bleeding (nephritic syndrome). WBC casts reflect interstitial inflammation (AIN or pyelonephritis). Fatty casts reflect lipiduria due to hyperlipidemia from severe proteinuria (nephrotic syndrome). Broad waxy casts reflect stasis in enlarged tubules of failing kidneys (CKD).

Step-by-Step Solution

1
Analyze the urinalysis finding of muddy brown granular casts.
Matches with acute tubular necrosis (ATN).
These casts represent necrotic tubular epithelial cells that have sloughed off into the tubular lumen due to toxic or ischemic injury.
2
Analyze the finding of red blood cell (RBC) casts.
Matches with nephritic syndrome.
RBC casts form when red blood cells pass through an inflamed and damaged glomerular basement membrane into the tubules.
3
Analyze the finding of white blood cell (WBC) casts.
Matches with acute interstitial nephritis or pyelonephritis.
WBC casts indicate inflammation in the tubulointerstitium (infection or allergic reaction) rather than the glomerulus.
4
Analyze the finding of fatty casts with a 'Maltese cross' appearance.
Matches with nephrotic syndrome.
Nephrotic syndrome is characterized by heavy proteinuria, leading to compensatory hyperlipidemia and subsequent lipiduria.
5
Analyze the finding of broad waxy casts.
Matches with chronic kidney disease.
Broad waxy casts form in dilated, hypertrophic tubules that have reduced flow in the setting of advanced and chronic renal disease.

Key Concept

Urinalysis cast patterns and associated renal pathologies
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Topics

Nephrology

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