Brown urine discoloration can stem from numerous causes of red urine. Old clot sediment can appear brown when suspended in urine of a certain concentration. Likewise, myoglobinuria and hemoglobinuria often appear brown in color. Medical renal disease can also produce brown urine discoloration. One classic example is the "muddy brown urine" observed in acute tubular necrosis. Highly concentrated urine in dehydration can give the appearance of dark or brownish urine. Merely becoming rehydrated with fluids is usually diagnostic and curative.
The commonly used antibiotics nitrofurantoin and metronidazole can lead to brown urine discoloration. Chloroquine and primaquine have also been implicated. Certain laxatives, as noted elsewhere, can also be causative. Additionally, the consumption of fava beans and aloe has been believed to cause urine to turn brown. A more serious cause of brown urine is liver failure with elevated circulating levels of bilirubin, which may first be evident in jaundice with yellowing of the skin and sclera.
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Cite this: Bradley Schwartz. Fast Five Quiz: Urine Discoloration - Medscape - Oct 22, 2021.