Why Is This Foley Bag Purple?

A 79-year-old male with a past medical history of paroxysmal atrial fibrillation and insulin-dependent diabetes presented to the emergency department with generalized weakness. He was found to be hypothermic at 34.2 Celcius rectally, tachycardic at 140 bpm and in atrial fibrillation. He had a stable blood pressure and respiratory status.

The patient had a urinary catheter placed two weeks prior due to acute urinary retention while on vacation in India. During the last two weeks, he became progressively weaker, with poor food intake. Purple urine bag syndrome (PUBS) is a purple discoloration of urine within the catheter bag and can occur over the span of hours to days. It is found in patients with indwelling urinary catheters, poor gastrointestinal motility, and alkaline urine.1 The pathophysiology occurs with digestion of tryptophan by gut bacteria to indole to indoxyl sulphate by the liver and excretion via urine. Commonly Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, or Proteus mirabilis in the urine will convert the indoxyl sulphate to indigo (blue) and indirubin (red color) resulting in the purple hue. Treatment involves urinary catheter exchange, antibiotics for urinary tract infection (as warranted), and treating for associated conditions, such as constipation.2

The patient received fluid resuscitation, external rewarming and piperacillin-tazobactam with improvement in the patient’s vital signs. His initial urinalysis was nitrite and leukocyte esterase positive with a pH of 8.5. The urine culture grew ESBL E.coli and Proteus. He was admitted and additionally diagnosed with diabetic gastroparesis, continued piperacillin-tazobactam for treatment of uninary tract infection, and discharged home on hospital day number five.


Dr. Koo is faculty and an emergency physician at MedStar Washington Hospital Center in Washington, D.C., and St. Mary’s Hospital in Leonardtown, Maryland.

  1. Al-Sardar H, Haroon D. Purple urinary bag syndrome. Am J Med.2009;122(10):e1-e2.
  2. Johnson JR. Purple urine bag syndrome. JAMA. 2012;307(18):1913.