Purple Urine Bag Syndrome, A Striking And Alarming Medical Phenomenon

Posted by Harshal Deshpande on Sun, Jan 13, 2019  
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Purple urine bag syndrome (PUBS), a rare medical phenomenon is rarely observed in clinical practice. The condition is characterized by purple discoloration of the urine due to recurrent urinary tract infections. The present article highlights the significance of this medcial uncommon entity

PUBS  typically develops after recurrent urinary tract infections due to gram-negative bacteria containing sulphatase and phosphatase enzymes. The purple discoloration of the catheter tubing is a major concern for the patients as well as for the physician. This results in the formation of pigments; indirubin (red) and indigo (blue), the mixture of which turns the urine purple. PUBS by itself appears to be asymptomatic or harmless.


The first report of PUBS was reported in 1978. Being a rare condition, the prevalence of PUBS has been documented unevenly in different series ranging from as low as 8.3% to as high as 42.1% in patients with long-term indwelling urinary catheter use. 

Risk factors

•    Increased tryptophan dietary content  

•    Increased alkalinity of the urine

•    Severe constipation 

•    Chronic indwelling urinary catheterization  

•    High urinary bacterial load  


The abnormal color of the urine has always been an alarming hue for the physicians in PUBS. The pathogenesis of PUBS has been associated with multiple bacterial urinary tract infections namely Providencia stuartti, Proteus mirabilis, Pseudomonas auruginosa, Klebsiella pneumoniae, Escherichia coli, Morganella, and Citrobacter species and Enterococci.

Actual biochemistry behind PUBS

A series of biochemical conversion reactions starting from deamination of tryptophan to indole, pyruvic acid and ammonia are involved behind the color change of the urine. These reactions are followed by conjugation of indole to indoxyl sulfate (indican). Indican is then metabolized to indoxyl,  which undergoes oxidation in the presence of alkaline urine and produces two main pigments-indigo (blue) and indirubin (red) which reacts with plastic Polyvinyl chloride (PVC) of the catheter tubing of the urine bag. This ultimately results in purple discoloration. The urine itself is not discolored to purple color but the infected urine usually has a dirty brown color.

Probable susceptibility

The probability for the PUBS syndrome is usually witnessed in elderly women patients with recurring urinary tract infections. Patients with chronic debilitation in spinal cord injuries are more prone to development of PUBS. .  Case reports have been reported in PUBS  patients assosciated with haemodialysis dependent chronic renal failure.


Apart from the urine discoloration, PUBS is almost similar to those experienced in a urinary tract infection which includes:

•    Increased spasms

•    A headache and nausea

•    Mild low back pain

•    Fever or chills

•    Presence of blood or deposits in the urine

•    Foul odor to the urine


Since PUBS is a benign process, family, friends and healthcare workers who are unaware of this medical entity tend to become alarmed because of the sudden baffling discoloration. However, physicians should be aware of the fact that this syndrome signals overlying recurrent Urinary Tract Infections (UTIs), because of improper care of the urinary catheters and improper sanitation.


Though purple urine bag syndrome seems harmless, treatment underlying UTI is directed. Medical management of purple urine bag syndrome does not require any special treatment apart from changing the catheter and control of constipation. Control of constipation and good urologic sanitation is recommended.  Appropriate antibiotic treatment of ciprofloxacin is sometimes helpful. Few cases of  PUBS owing to increased urine alkalinity and PVC containing urinary bags have been reported. However, definitive studies are required to further elucidate morbidity and mortality implications, to successfully combat this unusual phenomenon.

Thus, if your urine turns blue or purple, visit your doctor immediately. Since the exact cause of this phenomenon is still unclear, seeking medical help will certainly help to conclude the line of treatment. 

Keywords: Purple urine, discoloration, catheters, rare, antibiotic, UTIs, indigo


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