Purple urine

Abstract

20-year-old G1P0 patient with a gestation of 35 weeks and sickle cell anemia. She was hospitalized for pain associated with vaso-occlusive crisis and community-acquired pneumonia. During your stay in the semi-intensive care unit, you have purple urine. Subsequent urine culture confirms urinary tract infection by Proteus mirabilis.
Purple urine is a rare condition that tends to affect the elderly population and in association with prolonged bladder catheterization, although it can occur in patients with debilitating chronic pathologies, immobility, and symptoms of constipation or intestinal obstruction.
It is produced by the presence, in alkaline urine, of high concentrations of bacteria with indoxylsulfatase / phosphatase activity, including the genera Proteus, Pseudomonas, Morganella and Citrobacter. The purple color is a consequence of the conversion of indoxyl sulfate (a metabolite of the natural excretion of tryptophan) into indoxyl, under the effect of bacterial enzymes of the sulfatase / phosphatase type. Indoxil converts to indigo (blue) and indirubin (red) upon oxidation, a process that can take several hours. This urine tends to have a normal color initially and then, when combining the aforementioned colors, it takes on the characteristic purple tone.