Purple urine bag syndrome (PUBS)

Purple urine bag syndrome (PUBS) is a condition in which the urine bag and tubing of chronically catheterized patients turn purple.

• first medical description of PUBS was 1978, by Barlow and Dickson (1)

Prevalence of PUBS is variable, depending on patients population and bacterial epidemiology

• occurs in around 10-15% of patients with long term indwelling catheter (2)

Pathophysiology:

• a sequence of reactions beginning with dietary intake of tryptophan
  • tryptophan deamination to indole, hepatic conjugation to indoxyl sulphate, bacterial enzyme action to produce indoxyl and further substrate oxidation in the urinary tract results in the production of indigo and indirubin pigments
    • pigments combine, causing striking purple staining of the PVC lining of the urinary catheter bag (3)
      
      
  • production of the pigments arises from the action of an enzyme, the indoxyl sulphatase, procuced by a spectrum of bacteria like Escherichia Coli and Klebsiella Pneumoniae, upon the indowyl sulphate
    • pigments adhere to the catheter and the bag, and urine is discolored from red to blue to become purple
      • urine may be differently discolored between the catheter and the urine bag
    • it's important to mention that the urine itself isn't discolored (2)
    • urine bacteriological sampling is usually dark brown and turpid.
    • purple aspect concern urine contained in the catheter and its collecting bag (2)

Risk factors (4):

• risk factors include:
  • constipation
  • female gender
  • high bacterial load in the urinary tract
  • an alkaline urine environment - alkaline urine facilitate pigments precipitation in the synthetic materials of the urine catheter and bag, even though some reports described PUBS in acidic urines.
    
  • a diet rich in tryptophan
  • polyvinyl chloride urine bags
    
    
• increased incidence of PUBS in patients on haemodialysis with chronic kidney disease
  • as indoxyl sulphate is bound to albumin with a limited removal during dialysis and an increase of its serum concentration
    
    

Management (5):

• clinician's choice whether to give antibiotic treatment for resolution - no guidelines re: management exist (5)
  • indications for antibiotic therapy include symptomatic UTI, sepsis and signs of contiguous areas of infection or if the PUBS persist or occurs in an immunosuppressed patient
• in all PUBS medical management includes the treatment of underlying constipation and good catheter care including exchange in order to not only to prevent PUBS but also bring about its resolution

Notes:

• a similar phenomenon has been described in infants born with a genetic metabolic disorder called Drummond's Syndrome or blue diaper syndrome
  • a rare inborn error metabolism characterized by the incomplete intestinal breakdown and absorption of tryptophan that is then metabolized to indoles, absorbed and then excreted in the urine, which becomes stained in blue on infant's diapers (indoluria)

Reference:

• Barlow G, Dickson J. Purple urine bags. Lancet. 1978;28:220-221.
• Karray O et al. Purple urine bag syndrome, a disturbing urine discoloration.Urol Case Rep. 2018 Jun 28;20:57-59
• Shiao CC, Weng CY, Chuang JC, Huang MS, Chen ZY. Purple urine bag syndrome: a community-based study and literature review. Nephrology (Carlton) 2008;13:554-9.
• Dealler SF, Hawkey PM, Millar MR. Enzymatic degradation of urinary indoxyl sulfate by providencia stuartii and Klebsiella pneumonia causes the purple urine bag syndrome. J Clin Microbiol 1988;26:2152-6.
• Worku DA. Purple urine bag syndrome: An unusual but important manifestation of urinary tract infection. Case report and literature review.SAGE Open Med Case Rep. 2019