Examkin

Question

Difficulty: EasyNephrology

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

  • Muddy brown granular castsAcute tubular necrosis
  • Red blood cell castsAcute glomerulonephritis
  • White blood cell castsAcute interstitial nephritis
  • Fatty casts with a 'Maltese cross' appearanceNephrotic syndrome
  • Broad, waxy castsAdvanced chronic kidney disease

Answer

Muddy brown granular casts match with Acute tubular necrosis. Red blood cell casts match with Acute glomerulonephritis. White blood cell casts match with Acute interstitial nephritis. Fatty casts match with Nephrotic syndrome. Broad, waxy casts match with Advanced chronic kidney disease.
Each type of urinary cast has a specific mechanism of formation that correlates with a distinct pathophysiology. Muddy brown casts reflect tubular necrosis. RBC casts indicate glomerular basement membrane injury. WBC casts indicate tubulointerstitial inflammation. Fatty casts indicate lipiduria from nephrotic syndrome. Broad waxy casts indicate dilated tubules in chronic kidney disease.

Step-by-Step Solution

1
Identify the etiology of muddy brown granular casts.
Associated with acute tubular necrosis (ATN).
Ischemia or nephrotoxins cause necrosis of tubular epithelial cells, which slough off and form these characteristic casts.
2
Identify the etiology of red blood cell (RBC) casts.
Associated with acute glomerulonephritis.
RBCs escape through a damaged glomerular basement membrane and get trapped in Tamm-Horsfall mucoprotein in the tubules.
3
Identify the etiology of white blood cell (WBC) casts.
Associated with acute interstitial nephritis or pyelonephritis.
Inflammation of the interstitium and tubules leads to WBC exudation and cast formation.
4
Identify the etiology of fatty casts.
Associated with nephrotic syndrome.
Massive proteinuria stimulates hepatic lipoprotein synthesis, leading to hyperlipidemia and lipiduria, forming fatty casts.
5
Identify the etiology of broad, waxy casts.
Associated with advanced chronic kidney disease.
Chronic kidney disease leads to tubular dilation and hypertrophy; slow urine flow allows casts to form and become waxy.

Key Concept

Classic urinalysis cast findings and their specific renal etiologies
Rate this question

Topics

Nephrology

More questions from this topic