42-year-old man has dark urine

One day after a 10-km race, a previously healthy 42-year-old man has dark urine. Which of the following is the most likely cause of these findings?

Option Acute glomerulonephritis
Renal infarct
Renal vein thrombosis

Correct answer

correct answer: E

Rhabdomyolysis (Choice E) occurs when muscle fibers break down, often due to stress (such as running a race), releasing myoglobin into the bloodstream, which can then damage the kidneys. The recent history of a race, as well as the urinalysis which is positive for blood on dipstick but negative for RBCs supports this diagnosis.
Acute glomerulonephritis (Choice A) usually results in red blood cells in the urine and is unlikely with no history of infection or other symptoms.

Hypovolemia (Choice B) can lead to acute renal failure by prerenal mechanism but would not cause a positive dipstick for blood. Renal infarct (Choice C) would present with severe pain and renal failure, as would renal vein thrombosis (Choice D).