Purple urine bag syndrome (PUBS)


Purple urine bag syndrome is a medical syndrome where purple discoloration of urine occurs in people with urinary catheters and co-existent urinary tract infection.

History: first reported in 1978

Etiology and biochemistry:

Associated with alkaline urine and certain types of bacterial urinary tract infections that produce sulphatase/phosphatase.

Indigo (blue) and indirubin (red) pigments are produced and mix to becomes shades of purple. The presence of these pigments in the urine can also stain the foley catheter tubing and its collection bag shades of blue or purple giving rise to the syndrome’s descriptive name.

The reagents begin with tryptophan from the food chain being metabolized by gut bacteria. This metabolic process produces indole, which is absorbed into portal circulation and converted into indoxyl sulphate in the liver, after a series of detoxification transformations.

Indoxyl sulphate is excessively excreted in the urine and is digested into indoxyl by the enzyme sulphatase/phosphatase produced by certain bacteria such as Pseudomonas aeruginosaProteus mirabilisMorganella morganiiEscherichia coli, and so on. Indoxyl then changes into indigo and indirubin in alkaline urine.
Treatment, management and prognosis:
PUB syndrome is considered to be harmless, does not influence the outcome of patients and disappears after treatment of the urinary tract infection. No special investigations should be undertaken.

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