Purple urine bag syndrome is a medical syndrome

Syndrome

In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...

 where purple discoloration of urine occurs in people with urinary catheters and co-existent urinary tract infection

Urinary tract infection

A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...

. Bacteria in the urine produce the enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 indoxyl phosphatase. This converts indoxyl sulfate

Indoxyl

In chemistry, indoxyl is a nitrogenous substance with the chemical formula: C8H7NO. Indoxyl is isomeric with oxindol and is obtained as an oily liquid....

 in the urine into the red and blue colored compounds indirubin and indigo

Indigo dye

Indigo dye is an organic compound with a distinctive blue color . Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo dye produced today — several thousand tons each year — is synthetic...

. The most commonly implicated bacteria are Providencia stuartii

Providencia stuartii

Providencia stuartii , is a Gram negative bacterium that is commonly found in soil, water, and sewage. P. stuartii is the most common of the 5 species found in the genus Providencia, with Providencia rettgeri, Providencia alcalifaciens, Providencia rustigianii, P heimbachae...

, Providencia rettgeri, Klebsiella pneumoniae

Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....

, Proteus mirabilis

Proteus mirabilis

Proteus mirabilis is a Gram-negative, facultatively anaerobic, rod shaped bacterium. It shows swarming motility, and urease activity. P. mirabilis causes 90% of all Proteus infections in humans.-Diagnosis:...

, Escherichia coli

Escherichia coli

Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

, Morganella morganii

Morganella morganii

Morganella morganii is a species of Gram-negative bacillus bacteria. It is oxidase-negative and conducts anaerobic respiration. It causes a disease known as Summer Diarrhea....

, and Pseudomonas aeruginosa

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

.

Signs and symptoms

People with purple urine bag syndrome usually do not complain of any symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

s. Purple discoloration of urine is often the only finding, frequently noted by carers http://cdn2.kevinmd.com/blog/wp-content/uploads/11f1-792745.gif .

Pathophysiology

Tryptophan

Tryptophan

Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...

 in the diet is metabolized by bacteria in the gastrointestinal tract

Gastrointestinal tract

The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

 to produce indole

Indole

Indole is an aromatic heterocyclic organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. Indole is a popular component of fragrances and the precursor to many pharmaceuticals. Compounds that contain an...

. Indole is absorbed into the blood by the intestine and passes to the liver. There, indole is coverted to indoxyl sulfate. Indoxyl sulfate is excreted in the urine. In purple urine bag syndrome, bacteria that colonize the urinary catheter convert the indoxyl sulfate to indirubin and indigo.

Epidemiology

Purple urine bag syndrome is more common in female nursing home

Nursing home

A nursing home, convalescent home, skilled nursing unit , care home, rest home, or old people's home provides a type of care of residents: it is a place of residence for people who require constant nursing care and have significant deficiencies with activities of daily living...

 residents. Other risk factors include alkaline urine, constipation, and polyvinyl chloride

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

catheter use.