Pigments excreted in urine are partially absorbed by urate sediments, which consists of cell debris and sedimented urinary components formed when the acidified urine is stored below room temperature. These urate sediments looks reddish or pink due to the presence of a main pigment first introduced by Simons in 1842 as uroerythrin,
From early clinical observations it is known that uroerythrin is present in every urine and increased amounts are observed in pathological states, e.g.metabolic disorders with high fever or tissue degradation.