Purple urine bag syndrome (PUBS) is a complication of urinary tract infections (UTIs) where catheter bags and tubing turn purple. It is alarming for patients, families, and clinicians; however, it is in itself a benign phenomenon. PUBS is the result of UTIs with specific bacteria that produce sulphatases and phosphatases which lead tryptophan metabolism to produce indigo (blue) and indirubin (red) pigments, a mixture of which becomes purple. Risk factors include female gender, immobility, constipation, chronic catheterisation, and renal disease. Management involves reassurance, antibiotics, and regular changing of catheters, although there are debates regarding how aggressively to treat and no official guidelines. Prognosis is good, but PUBS is associated with high morbidity and mortality due to the backgrounds of patients. Here, we review the literature available on PUBS, present a summary of case studies from the last five years, and propose the Oxford Urine Chart as a tool to aid such diagnoses.
Purple urine bag syndrome (PUBS) is a rare phenomenon which can be highly concerning and distressing for patients and their relatives. It is a complication of urinary tract infections (UTIs) in which patients produce purple urine in their catheter tubing and bags. This is a simple spot diagnosis; however, a lack of physician awareness can result in misdiagnosis and inappropriate treatments.
Surprisingly, PUBS has been known of for a long time. King George III had blue urine during a bout of chronic constipation [
The PubMed database was searched for all case reports concerning PUBS. Studies were limited to those published in English since January 2010. The following keywords were used: purple urine bag syndrome, PUBS, and case report. The reference lists of retrieved articles were also screened. The case reports are summarized in Table
A summary of case reports of PUBS in the last 5 years.
Case | Key details |
---|---|
Su et al. [ |
81-year-old woman; PC = fever, discoloured urine; RFs = bedridden, chronic catheterisation; Ix = urine with |
Al Montasir and Al Mustaque [ |
86-year-old female; PC = abdominal pain; PMH = osteoporosis, fractured hip, neurogenic bladder; RFs = bedridden, chronic catheterisation, constipation; Ix = alkaline urine with |
Agapakis et al. [ |
83-year-old female; PC = haematuria, fever; PMH = hypothyroidism, Alzheimer’s, colon cancer; RFs = bedridden, chronic catheterisation; Ix = misdiagnosed as haematuria, alkaline urine with |
Duff [ |
57-year-old female; PC = diffuse abdominal pain; PMH = transverse myelitis, recurrent UTIs, 2 C-sections; RFs = chronic catheterisation, colostomy bag; Ix = alkaline urine with |
Bhattarai et al. [ |
87-year-old female; PC = altered mental status; PMH = dementia, hypertension, hyperlipidaemia, recurrent UTIs, left nephrostomy tube, right ureteral stent, end-stage renal disease; RFs = bedridden, kidney disease, constipated; Ix alkaline urine with Enterococci/ |
Mohamad and Chong [ |
78-year-old female; PC = fever, vomiting; PMH = hyperlipidaemia, hypertension, dementia; RFs = bedridden, chronic catherisation; Ix = urine dip unremarkable, blood cultured |
Yaqub et al. [ |
83-year-old female; PC = nausea, vomiting, reduced oral intake, constipation, purple urine; PMH = dementia; RFs = bedridden, chronic catheterisation, recurrent UTIs; Ix = alkaline urine with |
Bocrie et al. [ |
87-year-old female; PC = postfall syndrome, urinary retention, faecaloma; RFs = catheter; Ix = asymptomatic bacteriuria ( |
Keenan and Thomas [ |
97-year-old man; PC = purple urine, constipation; PMH = prostate hyperplasia, urinary retention; RFs = chronic catheterisation; Ix = urine with |
Siu and Watanabe [ |
48-year-old man; PC = ischaemic encephalopathy after cardiac arrest; PMH = type 2 diabetes, coronary artery disease/bypass; RFs = recurrent UTIs, chronic catheterisation; Ix = alkaline urine with |
PUBS is a consequence of UTIs with bacteria which metabolise products of tryptophan to produce red and blue pigments. This is summarised in Figure
The aetiology of purple urine bag syndrome [
There are several bacteria, mostly Gram negative, which have been associated with PUBS. These include
There are several risk factors associated with PUBS. The main factors, summarised in Table
Risk factors for purple urine bag syndrome [
Risk factor | Mechanism |
---|---|
Female gender | Anatomy predisposed to UTIs |
Increased dietary tryptophan | Increased substrate for conversion |
Increased urine alkalinity | Facilitates indoxyl oxidation |
Severe constipation | Increased time and substrate for bacteria |
Chronic catheterisation | Increased UTI risk |
High urinary bacterial load | Bacterial sulphatase/phosphatase availability |
Renal failure | Impaired indoxyl sulphate clearance |
While PUBS can be made as a spot diagnosis, a clinician unaware of this phenomenon may misdiagnose it. There are several causes of altered colouration of urine, including haematuria, haemoglobinuria, myoglobinuria, nephrolithiasis, UTIs, food dyes, drugs, poisons, porphyria, and allkaptonuria. Every one of these conditions has significantly different causes and treatments to PUBS, and so, there is a risk of inappropriate management of patients or worse, administration of drugs with several side effects [
It is important to understand the wide variety of diagnoses that can be made from different colours of urine as this underlies any potential misdiagnosis. Anything from transparent- or straw-coloured urine to amber urine can indicate that patients are well hydrated or dehydrated, respectively. Foam in or fizzing of urine can indicate proteinuria which may be due to renal disease or excessive protein intake. If a patient’s urine is orange, there are a number of possible causes, such as dehydration, UTI, liver disease, biliary disease, food dye, isoniazid, sulfasalazine, and riboflavin. Red urine is assumed to be haematuria but can have a multitude of causes. Serious causes include UTI, pyelonephritis, nephrolithiasis, menstruation, malignancy, BPH, trauma, renal disease, catheterisation, iatrogenic, ibuprofen, rifampicin, warfarin, haemolytic anaemia, sickle cell, thalassaemia, TTP, ITP, transfusion reaction, porphyria, and haemoglobinuria; however, it can be caused by things as harmless as beets, carrots, and blackberries. Brown urine may indicate severe dehydration, paracetamol overdose, metronidazole, nitrofurantoin, haemolytic anaemia, porphyria, or melanoma. There are a number of causes for even darker, that is, black urine: iron, laxatives (cascara/senna), rhabdomyolysis, alpha-methyldopa, cresol, L-dopa, metronidazole, nitrofurantoin, methocarbamol, sorbitol, alcaptonuria, porphyria, and metastatic melanoma. Urine can even go blue-green due to pseudomonas UTIs, methylene blue, food dye, amitriptyline, breath mints, propofol, metoclopramide, promethazine, cimetidine, flupirtine, indomethacin, methocarbamol, tetrahydronaphthalene, zaleplon, biliverdin, blue diaper syndrome, herbicide, and again porphyria. White urine is caused by proteinuria, pyuria from UTI, chyluria, filariasis, lymphatic fistula, schistosomiasis, lipiduria, propofol infusion, urinary TB, hypercalciuria, hyperoxaluria, phosphaturia, lead, and mercury [
Given the variety of urinary colours and related causes, there is a risk of misdiagnosis; therefore, we have developed the “Oxford Urine Chart” (Figure
Oxford Urine Chart.
Given the wide range of differentials above, it is important to confirm PUBS diagnoses. There are several factors to consider in patient history and examination. The time course of the change in urine colour is important, especially if it occurs on exposure to air. Infections or tumours are suggested by urgency, frequency, and dysuria, though if an infection is the cause, it may be concurrent with PUBS. Colicky abdominal pains suggest renal stones. A smell of ammonia in urine points to an infection. Certain foods in patients’ diets such as blackberries, beets, and carrots may cause a urinary colour change, so it is important to quantify their intake and its time course. Prescription medications including warfarin, L-dopa, and ibuprofen as well as diagnostic dyes might be the causes, and so drug history is extremely important. Pelvic and rectal examination may be required. In terms of investigations, one should start with a urine dipstick test and if there are concerns, then consider urine microscopy, culture, and sensitivity tests and urea and electrolyte blood tests [
It is important to manage PUBS appropriately as it has a high morbidity and mortality relative to UTIs alone due to its contributing factors. One must treat the UTI (e.g., with ciprofloxacin) and any constipation as well as sanitation measures including replacing the catheter. Another approach is to use intravenous antibiotics if the PUBS persists or the patient is in an immunocompromised state [
Agapakis et al. describe an 83-year-old female patient who presented with haematuria and fever on a background of hypothyroidism, Alzheimer’s, and colon cancer. She was bedridden and had a long-term indwelling catheter. As a female with colon cancer and a long-term catheter, she was at increased risk of PUBS. Initially, her discoloured urine was misdiagnosed as haematuria, emphasising the need for a tool to prevent misdiagnosis such as the Oxford Urine Chart. Later, urine dip and cultures demonstrated alkaline urine infected with
Duff presents a case of a 57-year-old female who suffered with diffuse abdominal pain with a past medical history of transverse myelitis, recurrent UTIs, and two C-sections. She had a long-term indwelling catheter due to her transverse myelitis affecting her urinary control and had a colostomy having needed a bowel resection for bowel obstructions due to adhesions from her previous C-sections. Her gender, catheter, and colostomy all contributed to her risk of PUBS. Urinary investigations found alkaline urine with
Bhattarai et al. came across an 87-year-old female patient with altered mental status. Her vast past medical history included dementia, hypertension, hyperlipidaemia, recurrent UTIs, left nephrostomy tube, right ureteral stent, and end-stage renal disease. Her complex urological anatomy, recurrent UTIs, and poor renal function put her at risk of PUBS, not to mention she was bedridden and developed severe constipation. She was found to have alkaline urine with Enterococci and
Mohamad and Chong encountered a 78-year-old female who was feverish and vomiting with a background of hyperlipidaemia, hypertension, and dementia. Her primary risk factors for PUBS were that she was bedbound and chronically catheterised. Interestingly in this case, urine dip was unremarkable but blood cultures grew
Yaqub et al. describe an 83-year-old female with nausea, vomiting, reduced oral intake, constipation, and purple urine. She had a history of dementia, being bedridden, chronic catheterisation, and recurrent UTIs. Her risk factors include her gender, catheter, recurrent UTIs, and constipation. She had alkaline urine with
Al Montasir and Al Mustaque met an 86-year-old female with abdominal pain and a history of osteoporosis, fractured hip, and neurogenic bladder. She was bedridden, chronically catheterised, and constipated. Risk factors for PUBS in this case include neurogenic bladder, catheterisation, immobility, and constipation. This patient also had alkaline urine with
Bocrie et al. cared for an 87-year-old female with postfall syndrome and urinary retention for which she had a catheter and faecaloma, the latter two being particular risks for PUBS. Investigations yielded a diagnosis of asymptomatic bacteriuria due to
Keenan and Thompson, unlike in the other cases, dealt with a male patient with PUBS. He presented with purple urine and constipation on a background of benign prostatic hyperplasia and subsequent urinary retention. The constipation and urinary retention for which he had a long-term catheter put this gentleman at risk of PUBS. His urinary cultures grew
Su et al. were faced with an 81-year-old woman with fever and discoloured urine who was bedridden and chronically catheterised. Her catheter specimen of urine grew
Siu and Watanabe, like Keenan and Thompson, encountered a male with PUBS. This 48-year-old man presented with ischaemic encephalopathy after cardiac arrest. He was a type 2 diabetic and had a previous coronary artery bypass. He suffered from recurrent UTIs subsequent to the encephalopathy requiring chronic catheterisation, increasing his risk of PUBS. He was found to have alkaline urine with
These cases illustrate the risk factors for PUBS very well. They emphasise female gender, alkaline urine, constipation, and long-term catheterisation as key factors in increasing the risk of PUBS. In most cases, the UTI was due to
PUBS is concerning for patients, families, and clinicians. It is a complication of mixed growth UTIs whereby the causal bacteria metabolise tryptophan to produce pigments that turn catheter bags purple. It tends to occur in elderly, immobile females with long-term indwelling catheters who might be constipated or in renal failure. This is a spot diagnosis but can be confirmed by history, examination, and urinary investigations. Management involves regular catheter changes and sanitation and possible treatment of UTIs and constipation depending on patient circumstances.
The authors declare that there is no conflict of interest regarding the publication of this paper.