But it's just as alarming as it sounds. 

By Maggie O'Neill
October 30, 2019

No, you're not looking at a random pouch with grape juice in it. The picture above is actually of a hospital bag filled with purple urine—yes, really.

The jarring photo came from a case report published Wednesday in the New England Journal of Medicine, which chronicles the story of a 70-year-old woman who came to the hospital after suffering a stroke. The woman had a urinary catheter inserted—or a tube that's placed into the body, usually the bladder, to drain liquid—and 10 days later, the urine that collected in the catheter appeared purple.

The authors of the report explained that the purple discoloration was thought to be caused by a chemical reaction of certain bacteria in an alkaline environment. The woman, however, showed no clinical signs of infection, per the case report, so doctors didn't treat her with antibiotics. The woman did, however, receive intravenous hydration. 

RELATED: Gotta Go? 13 Reasons for Urine Trouble

Purple urine sounds like something that would only happen under incredibly rare circumstances, but it's actually more common than you might think—aka, that it happens at all. A condition called Purple Urine Bag Syndrome (PUBS), was first reported in the 1970s and defined as the manifestation of an infected urinary tract, according to a paper published in the Journal of Family Medicine and Primary Care. (Just FYI: The patient in the case report did test for leukocytes in her urine, which can be a sign of a urinary tract infection, though she was not diagnosed with one.)

PUBS is uncommon, but, according to the previously referenced report, it affects just shy of 10% of institutionalized patients who depend on a catheter long-term. High levels of bacteria in the urine can cause PUBS. Some doctors think that it turns purple when dietary tryptophan is metabolized (or broken down) in the body. Other bacteria that have been linked to purple urine include Pseudomonas aeruginosa, Providencia stuartii, Escherichia coli, and enterococcus species, per the case report.

RELATED: What Your Urine Color Says About Your Health

Constipation has been linked to PUBS, the research says. “PUBS is most often observed in chronically catheterized and constipated people,” the report in the Journal of Family Medicine and Primary Care says. It adds that PUBS is easily treatable, but that, “it is distressing for family, friends, and healthcare workers who are unaware of this phenomenon and tend to become unusually alarmed because of the sudden inexplicable discoloration of the urine and sometimes the urine bag.”

Thankfully, the purple urine of the patient in the New England Journal of Medicine report was resolved quickly and easily. After given intravenous fluids, the patient's purple urine cleared up after four days.

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