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Difficulty: EasyNephrology

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

  • Muddy brown granular castsAcute tubular necrosis
  • Red blood cell (RBC) castsGlomerulonephritis
  • White blood cell (WBC) castsAcute pyelonephritis
  • Fatty casts and oval fat bodiesNephrotic syndrome
  • Broad waxy castsAdvanced chronic kidney disease

Answer

Muddy brown granular casts match with Acute tubular necrosis; RBC casts match with Glomerulonephritis; WBC casts match with Acute pyelonephritis; Fatty casts match with Nephrotic syndrome; Broad waxy casts match with Advanced chronic kidney disease.
Urinalysis sediment provides crucial diagnostic information in nephrology. Casts take the shape of the distal tubules and collecting ducts where they form. Their composition directly reflects the underlying renal pathology: necrotic cells (muddy brown) in ATN, red blood cells in glomerulonephritis, white blood cells in tubulointerstitial inflammation, lipids in nephrotic syndrome, and dense, degenerated material (broad waxy) in dilated tubules of chronic kidney disease.

Step-by-Step Solution

1
Identify the cellular composition of the muddy brown granular cast.
Recognize that it contains necrotic tubular cells, pointing to Acute tubular necrosis.
Ischemia or nephrotoxins cause death of tubular cells which slough into the lumen and form casts.
2
Evaluate the significance of RBC casts.
Link RBC casts to Glomerulonephritis.
RBCs entering the tubules through a disrupted glomerular basement membrane get trapped in Tamm-Horsfall mucoprotein, forming casts.
3
Determine the origin of WBC casts.
Associate WBC casts with Acute pyelonephritis.
WBC casts confirm that the inflammation/infection is located within the kidney (tubulointerstitium) rather than the lower urinary tract.
4
Connect fatty casts to their pathophysiologic state.
Match fatty casts with Nephrotic syndrome.
Heavy proteinuria is accompanied by hyperlipidemia and lipiduria, leading to lipid droplets and oval fat bodies in the urine.
5
Understand the formation of broad waxy casts.
Link broad waxy casts to Advanced chronic kidney disease.
Decreased urine flow through dilated tubules in end-stage renal disease allows time for casts to become dense, waxy, and unusually broad.

Key Concept

Urinalysis Sediment Pathologies
Estimated Time:1m 0s
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Topics

Nephrology

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