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A Case of Purple Urine Bag Syndrome in an Elderly Woman
Affiliations: Department of Internal Medicine, Lutheran Medical Center, Brooklyn, NY
Abstract: Purple urine bag syndrome (PUBS) is a rare condition characterized by intense purple discoloration of the urine. Although typically benign, purple urine is not only alarming to patients but can signal the presence of a urinary tract infection. This article presents the case of an elderly nursing home resident whose urine became purple after insertion of an indwelling catheter. The case report is followed by a brief discussion of PUBS, including its documented risk factors, the chemical chain reaction involved in producing purple urine, and how healthcare providers should treat patients when PUBS is encountered.
Key words: Purple urine bag syndrome, urinary tract infections, chronic catheterization.
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Urine discoloration is commonly seen in persons of all ages and is frequently attributed to many causes, including diet, medications, and underlying medical illness. Although many cases of discolored urine are nonthreatening and easily resolved, its presence in older adults, especially in elderly nursing home patients, should prompt an investigation into an underlying medical etiology. Purple urine bag syndrome (PUBS) is an infrequent condition usually signifying a urinary tract infection (UTI) in patients with long-term indwelling catheters. Although little is known about the etiology and prevalence of this condition, previous case reports indicate PUBS occurs predominantly in women and can signal an increase in morbidity and mortality if the underlying cause is not treated. In this article, we describe the case of this rare phenomenon presenting in a female nursing home resident without a history of previous catheterization.
Case Report
A 71-year-old woman was brought to the emergency department from a nursing home for evaluation of lethargy and shortness of breath. She was afebrile and had normal vital signs. Her medical history included hypertension, chronic kidney disease (stage 3), pulmonary hypertension, and chronic constipation. Based on her symptoms, the patient was suspected to have sepsis and was admitted to the intermediate intensive care unit for urinary output monitoring. A Foley catheter was inserted, and a urinalysis was performed immediately after catheterization.
Several hours after the patient’s catheterization, bright purple urine was observed in her catheter tubing and bag (Figure). The urinalysis results revealed a UTI and a urinary pH of less than 7.4, indicating acidic urine. A urine culture showed the presence of Escherichia coli and Proteus mirabilis. We determined at that point that the patient had sepsis and PUBS secondary to a UTI.
The patient was treated with intravenous ciprofloxacin and improved clinically. Within the first 24 hours of admission, the purple urine had resolved. She was released back to the nursing home on hospital day 4 with a prescription to take oral ciprofloxacin for 3 days. She was asymptomatic and no follow-up urinalysis or cultures were obtained.
Discussion
Discolored urine is commonly encountered in the clinical care of elderly persons. Although most cases of discolored urine are benign, its discovery can be alarming to both patients and healthcare providers and should prompt investigation into its underlying cause. Normal urine color ranges from pale yellow to amber, and it can change throughout an individual’s life depending on degree of hydration, age, sex, family history, and activity levels. Medications, certain foods, and medical conditions have been associated with abnormal urine colors, including red, orange, blue, green, dark brown, and purple.1,2 What follows is a brief discussion of the prevalence and risk factors of purple urine in elderly persons and what to do when encountering PUBS in catheterized long-term care patients.
Prevalence and Risk Factors of PUBS
The first case of PUBS was reported in 1978.3 PUBS is considered a rare event; however, most reports of PUBS have been published as individual case reports, so the exact prevalence of this entity is not known. One study reported the prevalence of PUBS as high as 9.8% in institutionalized patients with long-term urinary catheters.4 Studies show this phenomenon is most commonly associated with UTIs occurring in catheterized, institutionalized patients, typically elderly women with numerous comorbidities and constipation.5,6 Alkaline urine (pH ≥7.5) is also commonly seen in patients with PUBS.5,6
Pathogenesis of PUBS
Our patient had many risk factors for PUBS, including older age, female sex, constipation, and a UTI. It is suspected that bacterial UTIs can facilitate the development of PUBS. The bacterial species most commonly associated with PUBS are Providencia spp, E coli, Proteus spp, Pseudomonas spp, Klebsiella pneumoniae, Morganella spp, and Enterococcus spp.1,5-7 Less commonly reported species include Citrobacter spp, Staphylococcus spp, Streptococcus spp, and Methicillin-resistant S aureus. E coli and P mirabilis, two species commonly associated with PUBS, were both isolated from our patient’s urine.
Tryptophan, an essential amino acid in the diet, is metabolized by bacteria in the gastrointestinal tract to produce indole, which is later converted to indoxyl sulfate (indican) in the liver. Oxidation of indican produces indigo (blue pigment) and indirubin (red pigment), which combine to give the purple color to urine.4,8,9 Gram-negative bacteria that produce sulfatase and phosphatase are also important in the formation of pigment.1
There several possible reasons why PUBS is rarely encountered despite the common occurrence of UTIs in elderly patients. PUBS likely requires the simultaneous presence of various factors: (1) UTI caused by sulphatase- and phosphatase-producing bacteria; (2) chronic catheterization; and (3) high tryptophan in the diet for the formation of the essential pigments (high-tryptophan foods include most poultry, shrimp, dairy products, nuts, and legumes).10 Not all bacterial organisms of the same species produce the phosphatase and sulphatase enzymes that form the blue and red pigments responsible for creating purple urine.1,4,5,7 Furthermore, a certain concentration of indigo and indirubin may be required for the pigment to become evident. Alkaline urine is considered a risk factor of PUBS because it can predispose the patient to bacterial growth5,11; however, Chung and associates12 reported a rare occurrence of PUBS in a patient with acidic urine. Our patient also did not have alkaline urine, indicating PUBS can occur regardless of urinary pH. The type of materials used to make catheters has also been reported to contribute to the development of PUBS. In a study of 157 catheterized patients, Su and colleagues13 found that polyvinyl chloride plastic Foley catheters were used in 12 of the 13 PUBS-affected patients. It is interesting to note that our case patient developed PUBS while a Foley catheter was inserted and that two of the most common bacterial species associated with PUBS—E coli and P mirabilis—were identified in the urine culture; however, as PUBS is typically associated with long-term catheterization and alkaline urine, and our case patient had acidic urine and was only catheterized for a few hours before purple urine manifested, this case represents an atypical presentation. The care team did not suspect a catheter-associated UTI because the urinalysis was performed immediately following catheterization.
Treating PUBS in Elderly Patients
The presence of purple urine should alert clinicians to the possibility of an underlying recurrent UTI, which can progress to life-threatening kidney infections, sepsis, and other complications if left untreated. The literature also reveals two reports of immunocompromised patients with PUBS progressing to Fournier’s gangrene, requiring aggressive debridement.14 Although further studies are needed to support standardized treatment guidelines of this unique syndrome, treatment should generally be targeted at the underlying cause, which is typically a UTI.8 In such cases, appropriate antimicrobial therapy is warranted. In addition, healthcare providers working in long-term care and hospital settings should ensure appropriate and hygienic use of urinary catheters to prevent recurrent UTIs in at-risk patients.9,15 To reduce risk, long-term indwelling catheters should only be used when necessary, and drainage bags and catheters should be changed on a regular basis.16 For further guidance, healthcare providers should refer to the Centers for Disease Control and Prevention’s Guideline for Prevention of Catheter-Associated Urinary Tract Infections report.
Conclusion
PUBS is a rare disorder that commonly occurs in women who are chronically catheterized, constipated, and have underlying comorbidities. Although relatively harmless and easily treatable, PUBS can be associated with significant morbidity and mortality if the underlying cause is not treated. In most cases, UTI is the cause of PUBS. Until further research provides evidence-based guidelines for the treatment of PUBS, clinicians should target treatment at the patient’s underlying medical problem. In the case of UTIs, appropriate antibiotic prescribing is essential, along with steps to prevent recurrence, such as by ensuring the appropriate and hygienic use of urinary catheters.
References
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Disclosures: The authors report no relevant financial relationships.
Address correspondence to: William Nassour, MD, Department of Internal Medicine, Lutheran Medical Center, 150 55th Street, Brooklyn, NY 11220; wnassour@lmcmc.com
