Acute tubular necrosis, rhabdomyolysis, contrast-material nephropathy

1. Big picture

This topic is about intrinsic acute kidney injury (AKI) due to tubular injury. The examiner wants you to recognize that:

Prolonged ischemia or toxins → tubular epithelial cell injury → tubular obstruction + back-leak + impaired concentrating ability → AKI.

The 3 core entities are connected:

Ischemia / nephrotoxins
        ↓
Acute tubular necrosis
        ↓
Intrinsic AKI pattern:
muddy brown casts + isosthenuria + FeNa usually >2%

Rhabdomyolysis and contrast-material nephropathy are special causes of toxic/ischemic tubular injury.

AKI is defined by KDIGO as an acute rise in serum creatinine ≥0.3 mg/dL within 48 hours, ≥1.5× baseline within 7 days, or urine output <0.5 mL/kg/hour for 6 hours. ([KDIGO][1])

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