Purple Urine Bag Syndrome and Associated Urinary Tract Infections
Summary
Purple Urine Bag Syndrome (PUBS) is a striking clinical phenomenon in which long-term indwelling urinary catheters develop a violet hue. This discolouration arises when tryptophan-derived indoxyl sulphate is metabolised by bacterial sulphatases and phosphatases to form indigo and indirubin pigments, which together impart a purple tint to urine collection systems. Predominantly observed in elderly, frail and catheterised patients—often with concurrent constipation, alkaline urine or renal impairment—PUBS is typically a marker of underlying urinary tract infection rather than a primary disease. While the condition itself is benign, it signals the presence of multi-species bacterial colonisation and can provoke considerable alarm among patients and caregivers. Management strategies centre on antimicrobial therapy tailored to culture results, catheter replacement and optimisation of hygiene and bowel function. Despite its rarity, PUBS emphasises the need for heightened surveillance of catheter-associated infections and underlines the broader interplay between host metabolism, microbiota and medical devices.
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Purple Urine Bag Syndrome and Associated Urinary Tract Infections publication trend
The graph below shows the total number of articles in purple urine bag syndrome and associated urinary tract infections across all publications each year (not limited to Nature Index journals).
Technical terms
Purple Urine Bag Syndrome: A condition in which urine and catheter bags turn violet due to bacterial conversion of metabolic precursors into coloured pigments.
Indoxyl sulphate: A metabolite derived from dietary tryptophan that acts as a substrate for pigment-producing bacterial enzymes.
Sulphatase: An enzyme produced by certain bacteria that removes sulphate groups from indoxyl sulphate, facilitating pigment formation.
Phosphatase: An enzyme produced by certain bacteria that removes phosphate groups from indoxyl sulphate, also aiding pigment production.
Indigo and indirubin: Blue and red oxidation products of indoxyl that combine to yield a purple hue in urinary catheters.
References
- Purple Urine Bag Syndrome: An Alarming Hue? A Brief Review of the Literature. International Journal of Nephrology (2011).
- Purple Urine Bag Syndrome: A Rare Spot Diagnosis. Disease Markers (2017).
- Purple Urine Bag Syndrome: A Peculiar Presentation of a Urinary Tract Infection. Cureus (2023).
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