aka Unusual Urine 005
A 76-year-old male nursing home resident with dementia and end-stage renal disease who was undergoing hemodialysis was admitted to the hospital after a syncopal episode that occurred during dialysis.
When a urinary catheter was placed, purple urine was drained. The urinalysis showed a pH of 9.0 and bacteriuria but no hematuria or pyuria
What is the biochemical cause of purple urine?
- Purple discoloration can occur in alkaline urine as a result of the degradation of indoxyl sulfate (indican), a metabolite of dietary tryptophan, into indigo (which is blue) and indirubin (which is red)
- Bacteria such as Providencia stuartii, Klebsiella pneumoniae, P. aeruginosa, Escherichia coli, and enterococcus species are most commonly implicated
- The clinical course is benign, and the urine typically clears with resolution of the bacteriuria and acidification of the urine.
LITFL Further Reading