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Difficulty: MediumNephrology

Match each clinical presentation with its most characteristic urinalysis finding.

  • A 35-year-old man who develops fever, a maculopapular rash, and rising creatinine two weeks after initiating nafcillin therapy for a staphylococcal infection.White blood cell casts
  • A 68-year-old man who experiences a significant rise in serum creatinine 48 hours following an angiogram with iodinated contrast.Muddy brown granular casts
  • A 24-year-old woman presenting with new-onset hypertension, periorbital edema, and dark, cola-colored urine.Red blood cell casts
  • A 45-year-old man presenting with severe lower extremity edema, frothy urine, and a serum albumin of 2.2 g/dL.Fatty casts and oval fat bodies

Answer

Acute interstitial nephritis pairs with WBC casts, contrast nephropathy pairs with muddy brown casts, nephritic syndrome pairs with RBC casts, and nephrotic syndrome pairs with fatty casts.
Each clinical scenario distinctly represents a classic nephrology syndrome: Acute Interstitial Nephritis is associated with WBC casts, Acute Tubular Necrosis with muddy brown casts, Nephritic Syndrome with RBC casts, and Nephrotic Syndrome with fatty casts. Matching the underlying pathophysiology to the correct urinary sediment is essential for accurate diagnosis.

Step-by-Step Solution

1
Analyze the first clinical vignette to identify the underlying pathology.
Fever, rash, and AKI after nafcillin suggests Acute Interstitial Nephritis (AIN).
AIN is classically triggered by medications like beta-lactams and presents with a classic triad of fever, rash, and eosinophilia or eosinophiluria.
2
Identify the characteristic cast associated with Acute Interstitial Nephritis.
White blood cell casts correctly match the nafcillin-induced AIN vignette.
Tubular inflammation in AIN leads to leukocyte exudation into the tubular lumen, forming WBC casts.
3
Analyze the second vignette involving radiocontrast exposure.
AKI following iodinated contrast administration points to contrast-induced Acute Tubular Necrosis (ATN).
Contrast media causes intense renal vasoconstriction and direct tubular toxicity, leading to ischemia and necrosis.
4
Identify the characteristic cast for Acute Tubular Necrosis.
Muddy brown granular casts correctly match the contrast-induced AKI vignette.
Necrotic tubular epithelial cells slough into the lumen and degrade into muddy brown casts.
5
Evaluate the third vignette noting hypertension, edema, and cola-colored urine.
This constellation of symptoms describes a nephritic syndrome, such as postinfectious glomerulonephritis.
Glomerular inflammation leads to hematuria (cola-colored urine) and volume retention.
6
Select the appropriate cast for nephritic syndrome.
Red blood cell casts match the nephritic vignette.
Red blood cells passing through inflamed glomeruli get trapped in Tamm-Horsfall mucoprotein in the tubules, forming RBC casts.
7
Examine the final vignette noting edema, frothy urine, and hypoalbuminemia.
These findings are the hallmark of nephrotic syndrome.
Massive proteinuria causes frothy urine and hypoalbuminemia, which in turn leads to severe edema.
8
Determine the urinalysis finding for nephrotic syndrome.
Fatty casts and oval fat bodies correctly match the nephrotic vignette.
Altered lipid metabolism and lipiduria in nephrotic syndrome result in fat droplets within sloughed tubular cells, known as oval fat bodies, and fatty casts.

Key Concept

Correlation of specific urinary sediment findings with corresponding renal pathologies
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Topics

Nephrology

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