A patient with purple discoloration of urine bag and concomitant COVID-19 infection

1. Discussion

Purple discoloration of the urine bag (purple urine bag syndrome) is a rare phenomenon due to urinary tract infections (UTI) by a variety of bacteria including Escherichia coli (E. coli), Proteus mirabilis, Klebsiella pneumonie or Providencia bacteria in patients with chronic indwelling catheters. The bacteria produce substances (sulphatase and/or phosphatase) that act on tryptophan, steroidal or bile-acid conjugates in the urine to produce indigo (blue) and indirubin (red) pigments which combine to give the purple color.^{1 , 2} It is seen most commonly in female patients or those with chronic constipation, chronic kidney disease (CKD), and alkaline urine.^{1 , 2} All cases of purple urine bag syndrome are patients with chronic indwelling urinary catheters.^{1 , 3}

This unusual occurrence can be very concerning and distressing for patients, their relatives, and care providers as it may resemble bleeding or tainting of the urine. The urinary bag discoloration may develop over a few hours or days.³

2. Visual case discussion

We describe a case report of a 77-year-old male patient with a history of a chronic indwelling urinary catheter, chronic constipation, Type 2 diabetes mellitus (on insulin and oral sitagliptin), hypertension, ischemic heart disease with coronary artery bypass grafting, chronic kidney disease (CKD), and bladder cancer for which he had radical cystectomy with bladder reconstruction. He presented to our Emergency Department (ED) with dull, non-radiating diffuse abdominal pain and mild upper respiratory symptoms and was found to have purple discoloration of his Foley's catheter urine bag. His urinary catheter was changed six days before the presentation.

The examination did not elicit any abnormality except a mild lower abdominal tenderness without signs of peritonitis. Point of care abdominal ultrasound was unremarkable.

ED investigations revealed a normal complete blood count and electrolytes. His renal function was unchanged from his baseline CKD. COVID-19 polymerase chain reaction test (PCR) was positive. A urine analysis had a pH of 9, was positive for Leucocyte esterase, Protein (3+) and negative for nitrates. VBG: pH 7.26 (7.35–7.45), HCO₃ 23 mmol/L (22–29 mmol/L), PCO₂ 6.8 kPa (5.3–6.6 kPa).

Due to a previous urinary tract infection with extended-spectrum beta-lactamase (ESBL) E. coli, the patient was given intravenous meropenem. The urinary catheter and the urine bag were changed, and the patient was discharged home on oral Nitrofurantoin and home isolation for 14 days. Subsequently, his urine culture grew Proteus Mirabilis which was sensitive to the oral antibiotic given. Purple urine bag syndrome has been established as rare phenomenon and commonly found in patients with chronic indwelling urinary catheters.

3. Questions and answers

• A
  color of urine in patients with purple urine bag discoloration is purple?

  • i
    True
  • ii
    False
• B
  What are the bacteria associated with the UTI in patients with purple discoloration of the urine bag?

  • I
    E. coli
  • II
    Proteus Mirabilis
  • III
    Klebsiella
  • IV
    Proteus
  • V
    All of the above

Answer A: False

The color of the urine in a patient with purple discoloration of the urine bag is not purple. While the infected urine sits in the bag for a while, chemical reactions with various metabolites including the tryptophan steroid and/or bile acids, leave a purple color on the urine bag and catheter.

Answer B: All of the above

The cases of purple urine bag discoloration have been reported with all of the above and several additional urinary pathogens. It is not related to a specific bacterial pathogen. However, every patient with this condition has a UTI with a chronic indwelling urinary catheter and a urine bag. (Figs. 1 and 2 )

Fig. 1.

The picture shows discoloration of the urine bag with some urine at the bottom of the bag and sediments in the tubing.

Fig. 2.

The urine container is on the right while the left container is filled with water for comparison.

Funding

None.

Declaration of Competing Interest

None.