How does Purple Urine Bag Syndrome relate to turkey?

Illustration for article titled How does Purple Urine Bag Syndrome relate to turkey?

Yes, this is an actual medical condition. Purple Urine Bag Syndrome is exactly what it sounds like - patients with catheters are alarmed to find that the urine in their collection bags turns a deep purple. It can last for as long as two years, and it can be set off by turkey. With the holidays coming, can you afford not to find out about this syndrome?


Few people are in a very good mood when they've got a catheter. Even fewer are in a good mood when they're constipated. But the mood provoked by seeing the tube, and then the bag attached to the catheter, turn purple, has to be the worst of all. Doctors have reported people around the world complaining that their urine turned red, blue, and dark purple in their urine collection bags. It came to be known as Purple Urine Bag Syndrome, which translates into Latin as "purpura urina sacculo," in case doctors ever want to dress it up. The two compounds responsible for this syndrome are indigo and indirubin, but they take a circuitous route to show up.

The route starts with tryptophan - yes, the kind found in milk and turkey. As it moves through the digestive system it is turned to indole, and then to indoxyl sulfate. Constipation keeps tryptophan in the intestine longer, and leaves more indoxyl sulfate going through the system. If everything were normal, indoxyl sulfate might stay as it is, and make its way out of the body in the urine. When people have Purple Urine Bag Syndrome, it has to share space with various kinds of bacteria. These bacteria, present in the urine as a result of infection, shear the indoxyl sulfate of its sulfate, leaving indoxyl. If the urine is alkaline, having a pH greater than 7, the indoxyl breaks down into indirubin and indigo. The exact ratio of these compounds decide the color of the urine. With certain bacteria, it has even turned green.


Treating Purple Urine Bag Syndrome is relatively simple in theory - just treat the bacterial infection. But people who have a catheter over a long period of time can be prone to infections, and some patients have the syndrome for two years. Worth it for turkey? You decide.

Amethyst Image: William Warby

Via NCBI, CMAJ, and Hindawi.

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Dr Emilio Lizardo

Over 20 years seeing patients and I have never seen this. You know what that means? Now I have to put someone with a catheter on a high tryptophan diet, give them constipating meds and wait for the infection to happen.