Purple Urine in the Catheter Bag
A 79-year-old female, symptom-free dialysis patient who was a resident in a nursing home drew attention due to purple urine in her catheter bag (Figure a). Purple urine bag syndrome (PUBS) is a rare discoloration of urine. Tryptophan is converted by bacteria in the gastrointestinal tract into indole. In the liver, conversion to 3-hydroxy-indole (CYP2E1) and sulfonation to indoxyl sulfate takes place (renal elimination). If catheter material is colonized, especially with gram-negative bacteria, indoxyl sulfate is converted into the dyes indigo and indorubin. Oxidation causes the urine to turn violet in color. In contrast to the very high overall incidence of bacteriuria in long-term urinary catheter users (daily incidence of 3–8%), PUBS is extremely rare. PUBS risk factors include female gender, alkaline urine, constipation, immobilization, residency in a care home, and chronic renal failure. Differential diagnoses comprise hematuria, porphyria, and medications. Treatment options include antibiogram-based infection therapy, elimination of constipation, and catheter replacement. Since a mixed culture of gram-negative bacteria was identified, antibiotic treatment was not performed, but instead only catheter replacement. Urine color normalized thereafter (Figure b).
Uta Hillebrand, Prof. Dr. med. Roland Schmitt, Medizinische Hochschule Hannover, Klinik für Nieren- und Hochdruckerkrankungen, email@example.com
Conflict of interest statement: The authors declare that no conflict of interest exists.
Translated from the original German by Christine Rye.
Cite this as: Hillebrand U, Schmitt R: Purple urine in the catheter bag. Dtsch Arztebl Int 2022; 119: 764. DOI: 10.3238/arztebl.m2022.0197