Her urine was full of alcohol.

The 61-year-old woman, who was seeking a liver transplant, insisted she had not been drinking. Her doctors hesitated to believe her.

The liver transplant team at the first hospital she visited ushered her into an alcohol abuse treatment program, suspecting she had lied to obscure an addiction that may have contributed to her failing organ, according to a case study published Monday in the journal Annals of Internal Medicine.

“Initially, our encounters were similar, leading our clinicians to believe that she was hiding an alcohol use disorder,” wrote the study’s authors, a group of researchers at the University of Pittsburgh School of Medicine and Medical Center.

Further investigation showed a strange alternative explanation: The woman suffered from “urinary auto-brewery syndrome,” the study said, which caused her bladder to make alcohol.

Curiously, the patient didn’t show any signs of intoxication when she visited the clinic. The high alcohol concentration of her urine should have caused visible impairments if she had consumed the alcohol that ended up in her bladder.

When the doctors drew blood and tested her plasma, they did not find any trace of ethanol. They tested the woman’s urine for ethyl glucuronide and ethyl sulfate, two chemicals the body produces as it metabolizes alcohol and then expels it through the urinary tract. Neither showed up in the lab tests.

But her urine did contain sugar and yeast — the two key ingredients for fermentation.

And ferment it did. Researchers found yeast-rich urine samples became increasingly alcoholic when the sugars were allowed to ferment in the lab. The same process, they theorized, might be happening inside the woman’s body.

The doctors decided the presence of alcohol in her urine, but nowhere else, was “best explained by yeast fermenting sugar in the bladder.” The yeast inside the woman’s body, which was closely related to the “brewer’s yeast” used to make beer, was probably making the ethanol that was showing up in her urine tests, the scientists concluded.

After all of the tests and experiments, the Pittsburgh woman with alcoholic urine was allowed to apply again for a liver transplant. It’s unclear whether she will receive a new organ.

“As a result of our experiment and new appreciation for her pathophysiology, she was reconsidered for liver transplantation,” the University of Pittsburgh study said.

The woman’s bladder brewery is not the first instance of auto-brewery syndrome documented by doctors.

A 46-year-old man pulled over on suspicion of drunken driving claimed he had a similar disorder, The Washington Post reported in October. He refused a breathalyzer but was taken to a hospital, where his blood alcohol level was determined to be more than twice the legal limit to drive a car. Scientists said in a study last year that fungi in the man’s gut were brewing alcohol that made him act drunk, even though he said he had not had a drop to drink.

Not all researchers agree auto-brewery syndrome exists. A review of medical literature published in 2000 concluded “to date none of the studies published supporting the theory have withstood close scrutiny.”

In the 20 years since then, several additional case studies and news reports have documented suspected instances of the syndrome. A more recent study, in 2019, concluded auto-brewery syndrome is “probably an underdiagnosed medical condition.”