Purple urine bag syndrome in a patient on haemodialysis
Authors: John Wing Li and Kamal Sud
Published online: 16 August 2021
A 77-year-old woman with a long term urinary catheter on haemodialysis complained of suprapubic discomfort
A 77‐year‐old woman with a long term urinary catheter on haemodialysis complained of suprapubic discomfort. The urinary bag was purple (Figure). Urine investigations showed pyuria, and culture grew multiple organisms. Purple urine bag syndrome was diagnosed. This syndrome is rarely reported in dialysis populations.1 Deaminated dietary tryptophan is conjugated to indoxyl sulfate by the liver, then excreted in urine where bacterial sulfatase and phosphatase metabolise it to produce indigo (blue) and indirubin (red) pigments, staining the urinary bag purple.2 Risk factors include chronic catherisation, constipation, urinary tract infection and renal failure.2 Our patient was treated successfully by appropriate antibiotics and catheter replacement.

Competing interests
No relevant disclosures.
References
- Ting IW, Wang R, Wu VC, et al. Purple urine bag syndrome in a hemodialysis patient. Kidney Int 2007; 71: 956.
- Kalsi DS, Ward J, Lee R, Handa A. Purple urine bag syndrome: a rare spot diagnosis. Dis Markers 2017; 2017: 9131872.
Provenance: Not commissioned; externally peer reviewed.