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Purple urine bag syndrome (PUBS) associated with strong alkaline urine

Umeki S.

Department of Medicine, Toshida-kai Kumeda Hospital.

Mechanisms for purple discoloration of the plastic urine bag in purple urine bag syndrome (PUBS) were investigated. Activities of bacterial indoxyl sulfatase catalyzing the conversion of indoxyl sulfate to indigo (or indirubin) were detected in strong alkaline liquid media but not in normal ones. These enzyme activities were particularly high in simple and combined cultures of Proteus mirabilis and/or Klebsiella pneumoniae. These results suggest that occurrence of PUBS is associated with strong alkaline urine as well as urinary tract infections induced by some species of bacteria with indoxyl sulfatase.

Purple Urine Bag Syndrome:A Case Report and Review of the Literature

Hsuan-Hwai Lin, Sheng-Jiun Li, Kao-Bin Su, and Lian-Shan Wu
Department of internal medicine, Army Forces Hualien General Hospital

Purple urine bag syndrome (PUBS) is a rare phenomenon associated with alkaline
urine as well as urinary tract infections induced by some species of bacteria with
indoxyl sulfatase/phosphatase. The purple material is found to be a mixture of
indirubin and indigo. It is most observed in chronically cathete-rized and constipated
women. We report a case of PUBS who is a man suffering diarrhea. Gender or
constipation is not the absolute criteria of PUBS. PUBS is one of catheter-associated
urinary treat infection. It is almost asymptomatic and infrequently causes bloodstream
infection. Although our patient died of sepsis, the infection did not originate from
urine. Urine culture revealed Klebsiella pneumoniae that was different from blood
culture. Most authors believed that it is unnecessary to treat patients with PUBS
aggressively. Frequent evacuation of urine bag and urological sanitation are important
in these patients. ( J Intern Med Taiwan 2002;13:209-212 )
Key Words:Purple urine bag syndrome,Indigo,Indirubin,Indican
The purple urine bag syndrome is an infrequent happening. Urinary catheterized
patient has a purple colored urine bag following urinary catheterization for hours to
days 1,2,3. This phenomenon is known to occur with alkaline urine as well as urinary
tract infection induced by some species of bacteria with indoxyl sulfatase/phosphatase.
It is most observed in chronically catheterized and constipated women 1. Several
bacterial species have been reported in association with PUBS including Providencia
stuartii, Providencia rettgeri, Klebsiella pneumoniae, Proteus mirabilis, Escherichia
coli, Morganella morganii, and Pseudomonas aeruginosa 1,3,4,6-9. Although the
definite chemical substrate is unknown, most of authors believe that it is a mixture of
indigo and indirubin 1,3,4,5,7,8. However, there were some cases who presented the
purple urine bag without indicanuria and the violet pigment may be either a steroidal
or bile acid conjugate 2,6.
Case report
A 79-year-old male was admitted to our hospital because of aspiration pneumonia
with acute re-spiratory failure. The patient had been well and was living in a nursing
home until one week before admission. After admission, urine catheterization was
performed to monitor his urine output due to sepsis. Intravenous antibiotic was
prescribed. Unfortunately his condition was unstable and ventilator-dependent. Three
months later, his urine bag turned purple (Fig.1) even though we had changed a new
one. And diarrhea was noted concurrently. Urinalysis revealed pH of 8.0, negative
nitrate test and numerous WBC. Klebsiella pneumoniae was isolated from the urine.
There was no trace of intake of medication, food co-loring, or special food items that
might alter the urine color during the hospitalization. Unfortunately, the patient died
of sepsis with multiple organ failure after the purple urine bag had presented for one
The etiology of PUBS is still a controversial issue. Most authors believe that indigo
and indirubin are the mixture of the purple color and those derived from mammalian
metabolism 1 (Fig.2). Tryptophan is metabolized at gastrointestinal tract by gut
bacteria and it produces indole that is absorbed into portal circulation. Indole is
converted into indoxyl sulphate after a series of detoxication transformations in the
liver. Indoxyl sulphate is excessively excreted into urine and is digested into indoxyl
by sulphatase/phosphatase produced by some bacteria such as Providencia stuartii,
Providencia rettgeri, Klebsiella pneumoniae, Proteus mirabilis, Escherichia coli,
Morganella morganii, Pseudomonas aeruginosa, etc. Indoxyl turned into indigo and
indirubin in alkaline urine. Indigo is blue and indirubin is red. While they mix
together, the color becomes purple.
The plastic urinary catheter drainage bags occasionally turn purple hours or days after
catheterization. The longer the same drainage system leaves in place, the more intense
the color becomes. The phenomenon was first reported in 1978 as purple urine bag
syndrome 9. It was known to occur with bacterial infection of the urinary tract with
chronic constipation. Chronic constipation is commonly associated with bacterial
overgrowth in the colon in which tryptophan has been converted to indol.
We summarized the published literatures on the purple urine bag syndrome.
Twenty-one patients were identified from eight articles selected by computer
generated searching of MEDLINE (1966 through 2001 Dec.) and CINAHL database
1-8. Twelve patients were female (12/21) and the others were not mentioned about
their gender (9/21) in these articles. No male case was presented definitely in these
eight articles. According to a prospective study of 1497 catheterized patients by
Tambyah et al.10, the incidence of catheter-associated urinary tract infection (CAUTI)
was much higher in women than in men. Their mean age was 56.0.There were 244
CAUTIs in 1497 catheterized patients (16.3%); 147 were female (66%) and 77 were
male (34%; relative risk, 1.7; 95% confidence interval, 1.6-2.0; P<0.001). So purple
urine bag syndrome that is also one of CAUTIs happened in those old age women
compares reasonable with this prospective study. Although most of authors thought
that the majority of PUBS occurred in elder, female, bedridden and constipated
patients, our case was an old man and suffered from diarrhea while the purple urine
bag was noted. So gender or constipation was not the absolute criteria of PUBS.
We analyzed those bacterial species that were isolated from the urine of purple urine
bags reported in eight articles. Five of urine bags were Providencia stuartii 1; four
were Proteus mirabilis 4; four were Pseudomonas aeruginosa 2,6; two were Klebsiella
pneumoniae 1,6; one was Providencia rettgeri 3; one was Escherichia coli 8; one was
Morganella morganii 8. Our bacterial culture of urine revealed Klebsiella pneumoniae.
Dealler SF et al.1 had designed an experiment that bacteria were tested for their
ability to produce indigo on agar containing indoxyl sulfate. Besides these species
mentioned above, there are some species of bacteria (Enterobacter agglomerans,
Yersinia enteroclitis, Providencia alcalifaciens and Staphylococcus aureus, etc.) could
produce blue colony on agar following incubation for 48 hours,
because those species also could generate sulphatase/phosphatase.
According to the reported articles, most of patients which presented PUBS were
asymptomatic. Even some authors advocated that it is unnecessary to treat patient
aggressively 4. Although our patient died ultimately, catheter-associated urinary tract
infection was not the prime cause of death because CAUTI infrequently induced
bloodstream infection 10.
In conclusion, PUBS is associated with alkaline urine as well as CAUTI induced by
some species of bacteria produced indoxyl sulfatase/phosphatase. When we deal with
this syndrome, it is unnecessary to perform tests other than microbiology and
biochemistry. PUBS is like CAUTI rarely symptomatic and infrequently causes
bloodstream infection. However, nosocomial CAUTIs comprise a huge silent
reservoir of antibiotic-resistant bacteria and yeasts 10. Thus, efforts to prevent
CAUTIs by improved catheter care and deployment of technologic advances designed
for prevention must continue to receive high priority in institutional infection control

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