Purple Urine Bag Syndrome (PUBS): a thread.

This week, I was called to see a patient on the Stroke ward as the nurses had reported purple urine in her catheter bag.

When I got there, it was purple alright...Twinkly Winky purple.

The patient was fairly well with it though, so I decided to do what all good doctors do...google it.

Turns out this is an actual thing! Purple Urine Bag Syndrome.

It is most frequently seen in elderly catheterised ladies and is associated with gram negative UTI. That being said, it can occur in anyone with a catheter.

Dietary tryptophan (found in chocolate and dairy and lots of other tasty stuff) is converted to Indole by intestinal bacteria, which is then absorbed and conjugated in the liver to form Indole Sulphate.

Indole Sulphate is excreted in urine and bacteria can convert this to Indoxyl, which, in alkaline environments, is oxidised to Indigo and Indirubin compounds.

Here’s a screenshot I stole.

These compounds react with the catheter bag to make it purple.

An important risk factor is constipation which is thought to promote intestinal bacterial overgrowth and hence lead to increased Indole Sulphate excretion.

Bacteria known to cause PUBS include Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterococcus species, Pseudomonas aeruginosa, Citrobacter species, amongst others.

So if you see purple urine in a catheter bag, think about constipation, which can often be missed.

Treatment should include antibiotic cover for UTI and consider a change of catheter.

I also enjoyed writing “Impression: PUBS” in the notes like I knew about this all along.