A 30-year-old man trapped under debris for several hours develops painful swollen thighs and dark urine. Urine dipstick is strongly positive for blood but microscopy shows fewer than 5 red cells per high power field. Serum creatinine is 4.1 mg/dL and creatine kinase is 42,000 U/L. The MOST likely cause of his acute kidney injury is:

• A Renal vein thrombosis
• B Immune complex mediated acute interstitial nephritis
• C Myoglobin cast nephropathy causing tubular injury ✓
• D Acute glomerular inflammation with haematuria

Explanation

Massive rhabdomyolysis releases myoglobin, which is freely filtered and precipitates in tubules causing pigment nephropathy, typically with muddy brown casts and a high fractional excretion of sodium. Myoglobin gives a positive dipstick reaction for blood while microscopy shows few or no red cells because there is no true haematuria. Aggressive isotonic fluid resuscitation before and after decompression is the mainstay of prevention.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.