A 27-year-old man is brought to the emergency department by his wife after finding him collapsed in their garage. His wife says he was recently fired from his job as an insurance claims adjuster and has been struggling to find work for the past month. He has no history of serious illness or hospitalizations. He does not take any medications. His temperature is 98.6°F (37.0°C), pulse is 90/min, respirations are 9/min, blood pressure is 130/80 mm Hg. Physical examination shows a stuporous man with depressed respirations and needle track marks on his left arm.
Which of the following is the most likely cause of the patient’s abnormal laboratory values?
B) Breakdown of muscle tissue
This patient presents with altered mental status, respiratory depression, and track marks on his arm, increasing suspicion of intravenous drug use. Drugs like opioids can cause significant central nervous system depression, which may lead to prolonged immobilization after falling unconscious. Rhabdomyolysis is an important consequence of drug intoxication and prolonged tissue compression. The breakdown of muscle tissue can cause the laboratory derangements seen in this patient which include hyperkalemia and increased creatinine and BUN, which are all due to cell lysis and subsequent acute kidney injury. The blood noted on urine dipstick testing is due to myoglobinuria rather than the presence of red blood cells in the urine, which is why urine microscopy does not demonstrate the presence of red blood cells.
Answer choice A: Acute gastrointestinal bleeding, is incorrect. GI bleeding may cause altered mentation and tachycardia especially if there is an active significant bleed and may thus cause ischemia-associated acute kidney injury. However, the patient does not have any risk factors for GI bleeding, and his hemoglobin is normal. Moreover, his clinical history and physical examination point more toward drug use and prolonged immobilization.
Answer choice C: Decreased fluid intake, is incorrect. Loss of consciousness for long durations can lead to decreased fluid intake and thus cause ischemia-associated acute kidney injury. However, hypovolemia will not explain the presence blood on urine dipstick.
Answer choice D: Hemorrhagic stroke, is incorrect. Although hemorrhagic stroke may present acutely and cause altered mentation, it does not adequately explain the patient’s hyperkalemia, acute kidney injury, and blood in the urine.
Answer choice E: Urinary tract infection, is incorrect. Urinary tract infection may show positive blood on the urinalysis. However, the patient’s clinical picture and the lack of evidence of bacteriuria make it less likely.
Key Learning Point
Rhabdomyolysis can result from prolonged immobilization and compression of muscle tissue. Laboratory findings will show hyperkalemia, increased BUN and creatinine, and positive blood on urine dipstick with few RBCs on urine microscopy.
