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Journal of The Association of Physicians of India ■ Vol. 64 ■ June 2016
91
Purple Urine Bag Syndrome
B Barman1, M Lyngdoh1, KG Lynrah2, SB Warjri3
Abstract
The purple urine bag syndrome (PUBS) i.e. purple discolouration of urine,
is an uncommon and alarming condition in patients with long term urinary
catheterisation. Though the condition is benign, it should draw immediate
attention to the possibility of an underlying urinary tract infection. The
postulated hypothesis for this unusual event is probably a chemical reaction
involving tryptophan from food in the gut. We report a case with this unusual
and interesting phenomenon in a 65 year old female.
Introduction
P
UBS is a rare disorder causing
discolouration of urine and urine
collection bags due to the presence
of indigo and indirubin pigment
produced by tryptophan metabolism.
This condition is most commonly
associated with alkaline urine, female
gender, constipation and urinary tract
infection. 1 Although this condition
is benign, it can be distressing for
patients, family members, and health
care workers who are unaware of this
entity. We present a case with this rare
phenomenon.
Case Report
A 65 year old bed ridden female,
with a history of type 2 diabetes mellitus
and dementia with old fracture of left
femur who had an indwelling urinary
catheter in place for last 3 months,
p resented to us in t he eme r gency
department with the complaints of
nausea, vomiting, decreased oral
intake, chronic constipation and
purplish discolouration of the urine
bag and tubing (Figure 1). She was
hemody nam ically st able. P hysical
examination revealed mild palor and
features suggestive of left lower limb
deep vein thrombosis. Her urine bag
was filled with purple coloured urine
along with purplish discolouration of
the tubing and the bag. Investigation
revealed a haemoglobin of 9.8 gm/dl
and total leukocyte count of 8800/mm 3.
Her blood urea was 68 mg/dl, serum
creatinine 1.6 mg/dl, serum sodium 138
mEq/L, potassium 3.07 mEq/L, serum
protein 5.7 gm/dl with albumin 1.2 gm/
dl. Doppler study of left lower limb
was suggestive of deep vein thrombosis
(DVT). Urine microscopy revealed 4-5
leucocytes, 3-4 red blood cells and
calcium oxalate and phosphate crystals,
bacteria 3+ and albumin 2+. Urine
culture showed Escherichia coli and she
was started on injection Ceftriaxone.
Injection low molecular weight heparin
was given for DVT. She responded well
to treatment with disappearance of
purple urine colour.
Discussion
PUBS was first described by Barlow
and Dickson in 1978, 2 after purple
urine was found in a patient who had
prolonged urinary catheterization.
Interestingly, even a famous historical
figure, England’s King George III
(1738-1820) was believed to have been
affected by this syndrome or at least
a part of it. 3 The prevalence of PUBS
ranged from 8.3% to 42.1% in different
studies 4 but most of the published
data is based on case reports and
there is no data regarding prevalence
of this rare condition from Indian
The postulated hypothesis regarding
aetiopathogenesis of PUBS is believed
to be related to metabolites of dietary
tryptophan (Figure 3). 7 The normal
flora in the intestine metabolises
tryptophan to indole which is absorbed
into the portal circulation via the gut
wall. Liver conjugates indole into
indoxylsulphate which is excreted in
urine. Urinary bacteria produce an
enzyme indoxylsulphatase, breaking
down the indoxylsulphate into indoxyl.
Then indoxyl turns into indigo (blue in
colour ) and indirubin (red in colour ).
The mixture of these two substances
produces purple urine in the urinary
catheter and collection bag.
A strong association of PUBS with
constipation and intestinal obstruction
has also been described. Chronic
constipation alters gut motility and
prolonged transit time, resulting
bacterial overgrowth in the colon.
Bacterial flora containing tryptophase
converts tryptophan to indole and
indole is converted to indigo and
indirubin through a chain reaction that
gives urine purple colour. 8
Now, despite the common occurrence
of urinary tract infection with all the
risk factors of PUBS, it is interesting to
note the rarity of this syndrome. There
may be few possible explanations: PUBS
probably requires the simultaneous
presence of multiple risk factors, e.g.
Assistant Professor, 2Associate Professor, 3Senior Resident Doctor, Department of Medicine, North Eastern Indira Gandhi Regional
Institute of Health and Medical Sciences (NEIGRIHMS), Shillong, Meghalaya
Received: 28.07.2014; Revised: 20.05.2015; Accepted: 02.06.2015
1
Fig. 1: Purple colour urine
subcontinent. PUBS has been shown
to be associated with female gender,
constipation, advanced age, chronic
urinary catheterisation, urinary tract
infection and use of plastic urinary
catheter and bag. Higher bacterial load
in urine, in combination with the above
factors, facilitates the development of
PUBS. The bacteria most commonly
associated with PUBS are Escherichia
coli, Klebsiella pneumonia, Enterobacter
agglomerans, Pseudomonas aeroginosa,
Proteus spp., Provedencia species,
Enterococcus species, Streptococcus
spp., Staphylococcus spp., and even
MRSA. 5-6
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Journal of The Association of Physicians of India ■ Vol. 64 ■ June 2016
Tryptophan
Intestinal bacteria
Indole
Liver sulphation
Indoxylsulphate
Indoxyl sulphatase
Indoxyl
Indigo (blue)
Indirubin (red)
Purple –coloured urine
Fig. 3: The formation of indigo and
indirubin from tryptophan
presence of urinary tract infection
caused by sulphatase or phosphatase
producing bacteria, presence of high
tryptophan in diet, being catheterized
or constipated. Furthermore, a certain
concentration of the pigments may be
required for the precipitants to become
visible. The presence of alkaline urine
and also the type of materials used to
manufacture the urinary catheter and
bag may be important factors. PUBS
is more common following polyvinyl
chloride (PVC) plastic catheterisation;
PUBS following long term use of silicon
based catheter also has been reported
but is very rare. 5 Interestingly, PUBS
in the presence of acidic urine has also
been reported.
Most of the patients with PUBS
remain asymptomatic, its clinical
course is usually benign and therefore
only changing the urinary catheter and
urinary bag usually are enough to solve
the problem. Aggressive investigations
like urine culture or septic work up
and treatment with antibiotics are
usually not necessary. Antibiotic is
only indicated when there is concurrent
symptomatic urinary tract infection.
For asymptomatic patients, treatment
should be aimed at the underlying
medical problem rather than purple
bag itself and to reduce the likelihood
of this problem, it is important that the
drainage bags and indwelling catheters
may need to be changed on a regular
basis.
In conclusion, PUBS is a rare
manifestation of urinary tract
infection. It often occurs in chronically
catheterized and constipated patients
who have significant underlying
comorbidities. It has a relatively benign
course. Considering the known etiologic
and pathophysiologic mechanisms of
PUBS, it is surprising how rarely this
situation is observed and/or reported.
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