Urine Turning Black Upon Standing
The initially normal-colored urine slowly oxidizes and turns a dark brown or black color, a hallmark sign of homogentisic aciduria.
Description
A urine sample is collected in a clear container and left to stand at room temperature or is exposed to an alkaline agent. The practitioner visually monitors the sample over time for a distinct, specific color transformation caused by the oxidation of homogentisic acid.