Purple Rain: A Rare Spot Diagnosis

Purple rain urine

Case Presentation

A 70-year-old pleasant elderly male was brought in by his son, surprisingly complaining of purple-colored urine. The son got worried once he saw the purple urine bag and rushed his dad to the Emergency Department.

Upon further questioning, he reports a sweet elderly gentleman, known with previous cerebrovascular accidents, dysphasia and neurogenic bladder, that he has a urinary catheter inserted for. He claims that his dad has been having low appetite and passing less stool in the past week. Otherwise, he didn’t notice any other alarming symptoms. Furthermore, he denied noticing any fever, vomiting, behavioral changes indicating any pain, or recent change in his medications or diet. He had no known allergies as well. Upon full review of symptoms, chronic constipation was appreciated, otherwise, it was unremarkable.

Physical Exam

The patient was lying in bed, a bit uncomfortable, with an attached urinary catheter bag. He was afebrile and vitally stable. Proceeding with a focused physical examination, his chest was clear, and abdomen was soft, lax and nontender, furthermore, his skin had no rashes, and limbs were non-edematous. Inspecting the Urine Catheter Collection Bag, it did reveal Purple Urine Sediment.

Purple Urine in the Urinary Catheter Bag
Purple Urine in the Urinary Catheter Bag

Differential Diagnosis and Workup

Thinking of differential diagnoses of discolored urine, a purple urine bag is almost a spot diagnosis in our practice, definitely after ruling out any possible confounders if any.

We reassured the family and explained to them that we would order some blood and urine tests to confirm the diagnosis and start the appropriate treatment plan.

Case Management and Disposition

Laboratory test revealed mild leukocytosis with neutrophilia and mild elevated CRP. Otherwise, his urea, creatinine, liver function tests and electrolytes were reported normal.

Furthermore, a urine dipstick was done in the ED that reported positive for leukocytes, nitrites, and consequently sent to the lab for culture and full analysis which confirmed the diagnosis of a urinary tract infection (UTI).

We informed the son of the workup results, and a diagnosis of a UTI, given his leukocytosis, positive urine dipstick and the presence of a urinary catheter putting him at risk UTI. We reassured him about the urine color and explained the need to start antibiotics to cover the UTI, and changes the urinary catheter, which left us to explain only why was the urine purple unlike usual cases of UTI’s.

Critical Thinking and Take-home Tips

What is PUBS?

  • PUBS stands for Purple Urinary Bag Syndrome, first described in 1978.(1)
  • It is characterized by purple-colored urine collecting in urinary catheterization bags in patients known to prolonged urinary catheters. 
  • It presents asymptomatically and it is associated with urinary tract infections.
  • PUBS presents alarmingly to patients and family members, yet it is a benign phenomenon.

What causes the purplish discoloration of the urine in PUBS?

  • PUBS is associated with alkaline urine with a high bacterial load. 
  • It results due to UTI with certain bacteria producing sulphatases and phosphatases, which lead tryptophan metabolism to produce indigo (blue) and indirubin (red) pigments, a mixture of which becomes purple. (2)
  • Several bacterial species have been reported in association with PUBS including Providencia stuartii, Providencia rettgeri, Klebsiella pneumoniae, Proteus species, Escherichia coli, Enterococcus species, Morganella morganii, and Pseudomonas aeruginosa. (3)

What are the PUBS risk factors?

  • Female gender
  • Bedridden status or immobility
  • Chronic constipation leading to bacterial overgrowth
  • Renal disease
  • Prolonged urinary catheterization

What is PUBS management?

  • The reassurance of patient and family
  • Regular changing of urinary catheter
  • UTI Antibiotics coverage

What other urine colors should we be aware of?

  • Urine discoloration if a fairly common sign and indicates a certain pathology often that would need your attention as a physician.
  • Most urine discoloration is caused by food intakes, medications, dyes, or specific disease pathologies.
  • Red-colored urine is often related to hematuria, caused by multiple pathologies, including kidney stones, urinary tract injury or infection or cancer, amongst others.
  • Pink colored urine is often related to certain medications or dietary intake, i.e. beetroots and berries.
  • Brown or tea-colored urine indicates hepatobiliary disease or obstruction.
  • Green Urine can result due to medications such as Propofol.

What should I do when I encounter a discolored urine finding in my patient?

  • Remember always to have a systematic approach. 
  • Take a full history, including types or changes in medications history, diet changes, past medical history, and a full review of systems.
  • Keep in mind, some patients who are bedridden or elderly, communication and history taking might be limited; hence you will have to do your due diligence in gathering all the information you can get from family members, or available medical charts.
  • Your physical exam is a great asset as well in collecting information that can help you 

References and Further Reading

  1. Khan F, Chaudhry MA, Qureshi N, Cowley B. Purple urine bag syndrome: An Alarming Hue? A Brief Review of the Literature. Int J Nephrol 2011. 2011 419213. [PMC free article] [PubMed] [Google Scholar]
  2. Kalsi DS, Ward J, Lee R, Handa A. Purple Urine Bag Syndrome: A Rare Spot Diagnosis. Dis Markers. 2017;2017:9131872. doi:10.1155/2017/9131872
  3. Dilraj S. Kalsi, Joel Ward, Regent Lee, and Ashok Handa, “Purple Urine Bag Syndrome: A Rare Spot Diagnosis,” Disease Markers, vol. 2017, Article ID 9131872, 6 pages, 2017. https://doi.org/10.1155/2017/9131872.
  4. Al Montasir A, Al Mustaque A. Purple urine bag syndrome. J Family Med Prim Care. 2013;2(1):104–105. doi:10.4103/2249-4863.109970
  5. Traynor B P, Pomeroy E, Niall D. Purple urine bag syndrome: a case report and review of the literature. Oxford Medical Case Reports, Volume 2017, Issue 11, November 2017, omx059, https://doi.org/10.1093/omcr/omx059
  6. Lin CH, Huang HT, Chien CC, Tzeng DS, Lung FW. Purple urine bag syndrome in nursing homes: Ten elderly case reports and a literature review. Clin Interv Aging. 2008;3:729–34. [PMC free article] [PubMed] [Google Scholar]
Cite this article as: Shaza Karrar, "Purple Rain: A Rare Spot Diagnosis," in International Emergency Medicine Education Project, September 20, 2019, https://iem-student.org/2019/09/20/purple-rain-a-rare-spot-diagnosis/, date accessed: October 16, 2019

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