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A case of purple urine

Nicola Mumoli, Marco Cei
DOI: http://dx.doi.org/10.1093/qjmed/hcn108 147 First published online: 4 September 2008

An 88-year-old woman with a 10-year history of dementia presented because of severe dehydratation with hypernatremia. Two liters of fluid with electrolytes was administered intravenously and a urinary catheter was placed.

Three days later, the urine bag and the drainage system presented with an intense purple discoloration with normal color of the urine entering the catheter (Figure 1A).

Figure 1.

(A) showing purple discoloration of the urine bag and the drainage system with normal color of the urine. (B) Blue discoloration of the urine bag and the drainage system with normal color of the urine.

The results of urinalysis showed a pH of 9.0 with urine culture contained more than 100 000 colony-forming units of Klebsiella pneumoniae.

Levofloxacin was prescribed and 5 days later the urine gradually became yellow and clear.

Three months after discharge the patient returned because of abdominal pain and hypokalemia; a diagnosis of colonic pseudo-obstruction was made and with correction of the hypokalemia, the patient's abdominal pain rapidly resolved. Furthermore, 5 days after the new insertion of a urinary catheter, the plastic disposable urinary catheter bag turned blue (Figure 1B). The urine was alkaline and urine culture showed more than 100 000 colony-forming units of Proteus mirabilis.

Purple urine-bag syndrome (PUBS) is a uncommon phenomenon in which the contents of urine bags turn purple or blue following patient catheterization.

PUBS was more likely associated with the female gender and the presence of alkaline urine, constipation, institutionalization, the use of a plastic urinary catheter and certain bacteria such as Escherichia coli, P. mirabilis, Morganella morganii, K. pnemoniae and Providencia stuarti.

PUBS can occur in alkaline urine as a result of the degradation of indican, a metabolite of dietary tryptophan, into indigo (which is blue) and indirubin (which is red) by above Gram-negative bacteria. The clinical course is benign, and the urine typically clears with resolution of the bacteriuria and acidification of the urine.1

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