Purple Urine Bag Syndrome- An Alarming Situation

Purple urine bag syndrome (PUBS) is an uncommon condition that occurs mainly in chronically catheterized patient and associated with urinary tract infection. It is characterised by purple discolouration of urine bag which leads to significant stress and anxiety to patient, care takers and health workers, so awareness regarding this condition is of utmost importance. In our report, an old gentleman with Benign Prostate Hyperplasia (BPH) on per urethral catheter (PUC) with past history of recurrent urinary tract infection developed burning micturition of urine with purple discoloration of urine bag. After proper antibiotic and catheter changed, discoloration subsided. In India, as life expectancy and geriatric care is improving, more patients are on PUC for various diseases. So, the incidence of PUBS will increase and awareness is required about the condition and its management.

A 76-year-old male patient with a diagnosis of benign prostate hyperplasia on per urethral catheter (PUC) came to emergency with purple discoloration of urine bag and catheter since 4 days [Table/Fig-1]. He had a history of burning micturition for 8 days but not associated with any fever, abdominal pain, constipation, vomiting or any features suggesting of systemic infection. Genitalia examination was normal. Patient had a past history of recurrent urinary tract infections.

[Table/Fig-1]:

Purple discoloration of urine bag

Urine analysis showed alkaline urine (pH-7.6) with 20-30 white blood cells/high-power-field. Patient was started on oral nitrofurantoin, empirically. PUC was changed. Urine culture report showed Escherichia coli and growth was greater than 10⁵/mL. So the antibiotic was tailored according to culture sensitivity to injection ceftriaxone 1gm intravenous twice daily. After this, the purple discolouration of urine bag disappeared and following urine culture came out be sterile. Patient and his care takers were anxious about the condition. So, counselling and reassurance about the harmless nature of discoloration was done at the time of discharge.

Purple urine bag syndrome (PUBS) is yet an unusual condition but distressing for the patient and family members. It was first reported in 1978, usually in females with long term indwelling urinary catheter where urine colour turns purple [1]. Recurrent urinary tract infections (UTI) by the bacteria containing enzymes like sulphatase and phosphatase, results in the formation of pigments, indirubin (red) and indigo (blue). The mixture of these pigments lead to discoloration of urine colour to purple [2].

PUBS are an uncommon manifestation of urinary tract infection but the prevalence is increasing now-a-days [3]. It is associated with the female gender, alkaline urine, constipation, UTI, chronic kidney disease, dementia and use of polyvinyl chloride urinary catheter and bag [4].

The common organisms responsible for UTI are stuartti, Providenci rettgeri, Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas auruginosa, Morganella, Enterococci, and Group B Streptococci. Literature has shown that purple discoloration of urine is due to mixture of indigo and indirubin which are derived after deamination of tryptophan to indole that is absorbed into portal circulation. Indole is converted to indoxyl sulphate by hepatic conjugation and indoxyl sulphate is converted into indoxyl by indoxyl sulphatase enzyme produced by gut bacteria. The oxidation of indoxyl leads to formation of indigo (blue colour) and indirubin (red colour) in the urine and mixture of these colours impart a purple discolouration of urine [5,6].

Higher bacterial load facilitates the development of PUBS. Chronic constipation is usually associated with bacterial overgrowth in the colon which increases the likelihood of conversion of tryptophan into indole. Similarly, PUC associated UTI increases the conversion of indoxyl sulphate into indoxyl. So, PUBS is likely to observe in chronically catheterized and constipated individuals [6,7].

It is worth to note that despite of common occurrence of UTI in patients with risk factors for PUBS, this entity is not frequent in all patients of UTI. It could be due to simultaneous presence of multiple factors organism producing sulphatase and phosphatase enzyme, chronically catheterised or constipated patients, intake of diet rich in tryptophan.

Studies showed that not all organisms of the same species produce the phosphatase and sulphatase enzymes [7]. Moreover, a specific concentration of the pigments may be required for discoloration to become visible.

It has been seen that PUBS had progressed to Fournier’s gangrene in immunosuppressed patients and rates of morbidity and mortality increased [8]. Moreover in patients of chronic kidney disease (CKD) with PUBS, removal of Indoxyl sulphate during dialysis is limited as it is bound to albumin and which leads to exponential increase in serum indoxyl sulphate concentration. So when treating patients of CKD with PUBS, clinicians must always keep in mind about increased serum and urinary concentration of indoxyl sulphate, and that this uremic toxin is not only involved in the progression of CKD, but also leads to cardiovascular disease [9].

In India, as life expectancy and geriatric care is improving, more patients are on PUC for various diseases and the incidence of PUBS will increase. The condition is distressing to patient, family, and health care providers due to unawareness of this phenomenon and they usually become anxious by the discolouration of urine bag. So, clinician should be well verse with the condition and its treatment and can counsel the patient and family members about the disease and how to prevent it. Moreover, clinician should have in mind about its association with significant morbidity and mortality, if PUBS is associated with chronic kidney disease or in immunosuppressed patients.

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