Woman's Urine Turned Purple After Stroke

A French woman's urine turned purple after a stroke that saw her hospitalized, doctors have said.

In a case study published in The New England Journal of Medicine, Léo Plaçais and Christian Denier from the Hôpital de Bicêtre in Paris, France, said a 70-year-old woman had been admitted after an acute stroke. She was suffering from aphasia and hemiplegia—where brain damage causes a person to struggle with speech and moving the left side of their body. Because of her condition, a catheter had been inserted.

Ten days later, her physicians noticed her urine had turned purple. The team carried out tests on her urine and found the pH level was eight. This is higher than the average range for urine, which is around six. The lower the pH of urine, the more acidic it is. The higher, the more alkaline.

Further tests indicated the presence of Klebsiella pneumoniae—a common gut bacteria that can cause a range of health conditions, including pneumonia and meningitis. "The purple discoloration is thought to occur as a result of a chemical reaction facilitated by certain bacteria in alkaline environments," the case study said.

purple urine
Photo showing the woman's catheter. Doctors noticed the change to her urine color 10 days after she was admitted to hospital. New England Journal of Medicine 2019

It is thought that ingested tryptophan, an amino acid, was converted into indole, an organic compound, in the gut. This was then later metabolized by the liver, where it formed indoxyl sulfate.

"When excreted in the urine, indoxyl sulfate can be broken down by bacterial enzymes to form indigo and indirubin, which are blue and red, respectively, creating the color purple when combined," the doctors wrote.

They said several other bacteria are known to result in this reaction. Because the woman had no symptoms indicating infection from the bacteria, she was not treated with antibiotics. After about four days, her urine turned back to a normal color and the pH level dropped back down.

Cases of purple urine bag syndrome are relatively rare. However, in 2018 doctors in India reported the condition in a 70-year-old man. Published in BMJ Case Reports, the team explained that the man—who had had a catheter for six months—was alarmed when he noticed his urine had turned purple. Tests showed the bacteria Escherichia coli and he was treated with antibiotics.