Purple Urinary Bag Syndrome

Abstract

Purple urine bag syndrome is a rare condition that was first described in the literature in 1978.1Barlow G.B. Dickson J.A.S. Purple urine bags.Lancet. 1978; 1 ([letter]): 220-221Abstract PubMed Scopus (105) Google Scholar It is characterized by the purple discoloration of a catheter bag and tubing over hours to days (Figure 1, Figure 2). This phenomenon is due to the combination of bowel stasis, a complicated breakdown of tryptophan, and the presence of a urinary tract infection.Figure 2Purple urine bag.View Large Image Figure ViewerDownload (PPT) An 82-year-old frail man with hypertension, depression, previous alcohol dependence, and a cerebrovascular event was admitted via the Accident and Emergency Department following a fall. Three days later he developed abdominal pain, distention, and constipation. A clinical examination and an abdominal radiograph revealed a large bowel obstruction originating from the caecal area. Initial treatment was instigated, including fluids, nothing by mouth, and insertion of a nasogastric tube and urinary catheter. Due to his frailty and multiple comorbidities, it was deemed inappropriate to operate on him. He was treated conservatively, and 2 days later it was noticed that his catheter bag and its tubing had a purple discoloration. Urine analysis showed positive nitrites, 3+ leukocytes, 3+ protein, 1+ ketones, and a pH of 8.0. The urine culture showed a heavy growth of mixed organisms. Purple urinary bag syndrome is an uncommon process that occurs when patients with a catheter in situ develop constipation. The urine entering the catheter is normal in color, yet purple discoloration soon appears (Figure 1, Figure 2). This is due to the development of indigo (blue in color) and indirubin (red in color) by the presence of urinary bacteria. First of all, tryptophan from food is digested and metabolized by gut bacteria to produce indole, which in turn is converted to indoxyl sulphate by the liver. The indoxyl sulphate is converted to indoxyl in the presence of urinary bacteria by the enzyme indoxyl sulphatase, and finally, to the indicans by the presence of alkaline urine (Figure 3).2Dealler S.F. Hawkey P.M. Millar M.R. Enzymatic degradation of urinary indoxyl sulfate by Providencia stuartii and Klebsiella pneumoniae causes the purple urine bag syndrome.J Clin Microbiol. 1988; 26: 2152-2156PubMed Google Scholar, 3Stott A. Khan M. Robert C. Galpin I.J. Purple urine bag syndrome.Ann Clin Biochem. 1987; 24: 185-188PubMed Google Scholar The most common bacteria responsible for this phenomenon are Pseudomonas aeruginosa, Eschericha coli, Proteus mirabilis, Providencia rettgeri, Klebsiella pneumoniae, and Proteus vulgaris.2Dealler S.F. Hawkey P.M. Millar M.R. Enzymatic degradation of urinary indoxyl sulfate by Providencia stuartii and Klebsiella pneumoniae causes the purple urine bag syndrome.J Clin Microbiol. 1988; 26: 2152-2156PubMed Google Scholar, 4Vallego-Munzur F. Mireles-Cabodevila E. Varon J. Purple urine bag syndrome.Am J Emerg Med. 2005; 23: 521-524Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar It is apparent that the indicans interact with the plastic material of the catheter bag and tubing to produce the deep purple discoloration by producing a coating layer.1Barlow G.B. Dickson J.A.S. Purple urine bags.Lancet. 1978; 1 ([letter]): 220-221Abstract PubMed Scopus (105) Google Scholar, 3Stott A. Khan M. Robert C. Galpin I.J. Purple urine bag syndrome.Ann Clin Biochem. 1987; 24: 185-188PubMed Google Scholar Interestingly, when the urine is put in contact with other sterile urine containers, no color change takes place (Figure 4). The longer the urine is left in contact with the catheter plastic, the deeper the purple color produced. Constipation prolongs the transit time of tryptophan in the bowels. This results in an increase in levels of indoxyl sulphate in urine, and in the presence of alkaline urine, it turns a purple color.3 Purple urinary bag syndrome, although benign,5Robinson J. Purple urinary bag syndrome: a harmless but alarming problem.Br J Community Nurs. 2003; 8: 263-266Crossref PubMed Scopus (18) Google Scholar is an alarming condition that does not need aggressive antibiotic treatment, as it commonly resolves with good catheter management (ie, replacement). Purple urine bag syndrome is a benign condition seen in patients who have bowel stasis, a urinary catheter in situ, and an associated urinary tract infection.