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Woman’s urine turns PURPLE after rare side effect of extreme constipation and UTI

Doctors in Kentucky have detailed a rare case in which an elderly woman’s urine turned a dark purple due to a complication of a bladder infection.

The unidentified 76-year-old patient suffering from heart failure, kidney failure and bladder cancer was hospitalized and connected to a catheter to extract urine.

An infection in his urinary tract caused a biochemical reaction that produced blue and red pigments in his urine that, when oxidized in the catheter bag, turned a deep purple.

Doctors issued the rare diagnosis of purple urine bag syndrome (PUBS), which occurs in up to 42 percent of patients attached to long-term catheters.

A chemical reaction in the liver produces an indigo pigment and indirubin, a red pigment. Those pigments combine and oxidize to turn purple in the urinary sac.

Purple urine bag syndrome (PUBS) is often a complication of urinary tract infections (UTIs), as is the case with this 76-year-old woman, where the bags and catheter tubes they turn purple. Although almost always benign, the violent shade of purple can be alarming to patients, families, and doctors.

Doctors from the University of Pikeville in Kentucky revealed the case in the magazine Oxford Medical Case Reports.

Writing in the report, they said: ‘Elderly and bedridden patients with multiple comorbidities more frequently require long-term indwelling catheters which increase the risk of UTIs.

“These patients are more likely to be infected with rarer bacteria that can cause PUBS.”

The patient had a long history of serious medical problems, including congestive heart failure, chronic kidney disease, and bladder cancer.

He went to the hospital for shortness of breath related to his cardiovascular problems.

To drain her bladder, doctors hooked the woman up to a catheter and then treated her with intravenous medications to reduce inflammation related to congestive heart failure.

After four days in the hospital, the patient’s urine bag turned a violent purple hue.

Dipstick tests found her urine to be extremely alkaline with a pH of 8.5, a symptom that her kidneys were not working properly.

It also had high concentrations of the Proteus mirabilis bacterium, a common cause of complicated urinary tract infections.

PUBS was first described clinically in 1978.

The condition is almost always benign, but it can be alarming for patients and their loved ones.

In addition to age and frailty, female gender and renal failure, alkaline urine, and constipation are also primary risk factors.

The phenomenon is the result of a multi-step biological process in the intestine.

The bacteria help break down the amino acid tryptophan, which is converted to a compound called indole in the intestine, where it is then carried to the liver and converted to indoxyl sulfate.

Indoxyl sulfate is metabolized to indoxyl in the urine with the help of bacteria, which produce phosphatase and sulfatase.

Indoxyl is converted to indigo, the blue color, and indirubin, the red color, in alkaline urine, and these colors then mix to form a purple color.

Purple urine often tells doctors that the patient has a urinary tract infection, though not always.

Chronic constipation is commonly associated with bacterial overgrowth in the colon, which increases the conversion of tryptophan to indole.

Most people who experience PUBS will be fine, but immunocompromised patients are susceptible to serious illness, the doctors said. Fournier’s gangrene, for example, can arise as a result of urinary tract disease. It is a rare and life-threatening bacterial infection of the scrotum (which includes the testicles), penis, or perineum that causes death and sloughing of body tissue.

The doctors said: ‘The medical management of PUBS requires changing the catheter and giving appropriate antimicrobial therapy to treat the underlying bacterial infection.

‘Her constipation resolved and a 5-day course of antibiotics was completed. The patient was discharged to a nursing facility with recommendations for follow-up with her nephrologist and urologist as an outpatient.’


Doctors say that the bluish discoloration of urine is triggered by a series of chemical reactions in the body.

Bacteria responsible for the breakdown of tryptophan metabolites, an amino acid found in food.

This produces indole, which is converted to indoxl sulfate, which is then oxidized to blue indigo and reddish indirubin.

Doctors at King George Medical University in Lucknow, India, wrote in the British Medical Journal Case Reports last year: “The combination of indigo and indirubin gives the urine collection bag a purple hue.”

However, the discoloration is completely benign, and often the underlying UTI is considered more worrisome by clinicians.

Women face a higher risk of developing PUBS because they have a shorter urethra, which leaves them more vulnerable to getting UTIs.

Constipation can also increase the odds because it gives bacteria more time to break down tryptophan metabolites in the body.

It is not clear how common PUBS are, but it has been described as a “rare phenomenon”.