A 30-year-old man is admitted to the hospital due to seizures. The repeated, prolonged tonic-clonic seizures were terminated with intravenous lorazepam in the emergency department. Medical history is significant for amphetamine abuse. The patient develops decreased urine output 24 hours after hospital admission. Temperature is 37.1 C (98.8 F), blood pressure is 140/90 mm Hg, pulse is 88/min, and respirations are 18/min. Examination shows bibasilar lung crackles and mild edema of the lower extremities. Laboratory results are as follows: Which of the following is the most likely cause of this patient's kidney injury?

Question

A 30-year-old man is admitted to the hospital due to seizures.  The repeated, prolonged tonic-clonic seizures were terminated with intravenous lorazepam in the emergency department.  Medical history is significant for amphetamine abuse.  The patient develops decreased urine output 24 hours after hospital admission.  Temperature is 37.1 C (98.8 F), blood pressure is 140/90 mm Hg, pulse is 88/min, and respirations are 18/min.  Examination shows bibasilar lung crackles and mild edema of the lower extremities.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's kidney injury?

Quizplus · Accepted Answer

11ec160b_3a50_86de_9249_f59fa1ed1410_MD0001_00 This patient with acute kidney injury, hyperkalemia, and urinalysis with 3+ blood but no red blood cells has rhabdomyolysis, likely induced by his prolonged seizure. Rhabdomyolysis is characterized by myocyte injury with the release of intracellular muscle contents (ie, myoglobin, electrolytes) into the circulation. It is common in crush injuries, prolonged muscle activity (eg, seizure), or drug use. Positive blood on urine dipstick (a reaction that detects the heme pigment in both hemoglobin and myoglobin) in the absence of red blood cells on microscopic urinalysis suggests myoglobinuria. Renal injury in rhabdomyolysis results from myoglobin filtration and degradation within the glomeruli. Heme pigment is released, which causes acute tubular necrosis by direct cytotoxicity and renal vasoconstriction. Hyperkalemia, hyperphosphatemia, and hyperuricemia also occur due to myocyte lysis. (Choice A) Immune complex-mediated glomerular injury is seen in a variety of diseases (eg, IgA nephropathy, poststreptococcal glomerulonephritis), but these diseases do not cause myoglobinuria. Urinary cast formation or severe proteinuria are more common manifestations. (Choice B) Acute interstitial nephritis, an inflammatory reaction of the tubular interstitium, is typically associated with a medication exposure (eg, antibiotics) and presents with some combination of fever, eosinophilia, and rash. Urinalysis shows white blood cell casts, not myoglobinuria. (Choice C) Renal infarctions can be due to thromboembolic or atheroembolic disease and typically occur in older patients with established atherosclerosis or hypercoagulability. Hematuria with red cells would be expected on urinalysis. (Choice D) Multiple myeloma causes renal injury due to light chain-complex deposition in the renal tubules. This malignancy occurs in older patients and presents with hypercalcemia, anemia, and bone pain. It causes proteinuria (ie, Bence Jones protein), not myoglobinuria. (Choice E) Tubular injury due to released hemoglobin can also cause a heme pigment-induced kidney injury and may occur with hemolytic diseases (eg, paroxysmal nocturnal hemoglobinuria) or incompatible blood transfusion. However, renal failure after a prolonged seizure is more suggestive of rhabdomyolysis. Educational objective: Rhabdomyolysis is characterized by the release of intracellular muscle contents (eg, myoglobin, electrolytes) due to myocyte injury; it is common with crush injuries, seizures, or drug use (eg, statins). Heme pigment (released from myoglobin after degradation in the kidney) is toxic to tubular cells and can cause acute tubular necrosis. Positive blood on urine dipstick in the absence of red blood cells on microscopic urinalysis suggests myoglobinuria.

A 30-Year-Old Man Is Admitted to the Hospital Due to Seizures