A 74-year-old woman (with a history of urinary retention due to cerebral palsy) presented with aspiration pneumonia at our emergency department. During her stay in a nursing home, a bladder catheter was placed for an extended period.On admission, a urine bag with purple discolouration was found (Figure 1). We diagnosed the patient with purple urine bag syndrome (PUBS), which is a rare manifestation of urinary tract infection. Figure 1. Purple discoloration of the empty urinary bag and tube, with the proximal tube showing predominant bluish discoloration Bacteria such as Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Morganella morganii,and Enterobacter species produce an enzyme called indoxyl sulphatase/phosphatase that transforms urinary indoxyl sulphate, a residual product of metabolised dietary tryptophan to indigo (blue) and indirubin (red), which appear purple when combined.1 In PUBS, a purple discoloration is observed in the urine bag and on the indwelling catheter; however, the urine itself often does not markedly turn purple.2 PUBS occurs predominantly in chronically catheterised, constipated women and patients with chronic diseases, such as dementia, diabetic nephropathy, and those bedridden for long periods.3 The female urethra is more prone to bacterial infections because of its short length and proximity to the anus. Chronic constipation causes bacterial overgrowth in the intestine, and this enhances the metabolism of tryptophan to indole and results in high levels of indigo and indirubin in the urine.4Therefore, PUBS is predominantly observed in chronically constipated women. PUBS treatment should be aimed at the underlying medical problem rather than the bag coloration. Purple colour can disappear spontaneously or after treatment of infection. Examination of the urine bag should draw attention to a urinary tract infection, and the phenomenon should be explained to patients. In our case, urine cultures were positive for the species Escherichia coli and Proteus mirabilis(>100,000 colonies/mL). Following treatment with ciprofloxacin for pneumonia, the patients urine bag returned to a normal colour.

A 74-year-old woman (with a history of urinary retention due to cerebral palsy) presented with aspiration pneumonia at our emergency department. During her stay in a nursing home, a bladder catheter was placed for an extended period.On admission, a urine bag with purple discolouration was found (Figure 1). We diagnosed the patient with purple urine bag syndrome (PUBS), which is a rare manifestation of urinary tract infection. Figure 1. Purple discoloration of the empty urinary bag and tube, with the proximal tube showing predominant bluish discoloration Bacteria such as Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Morganella morganii,and Enterobacter species produce an enzyme called indoxyl sulphatase/phosphatase that transforms urinary indoxyl sulphate, a residual product of metabolised dietary tryptophan to indigo (blue) and indirubin (red), which appear purple when combined.1 In PUBS, a purple discoloration is observed in the urine bag and on the indwelling catheter; however, the urine itself often does not markedly turn purple.2 PUBS occurs predominantly in chronically catheterised, constipated women and patients with chronic diseases, such as dementia, diabetic nephropathy, and those bedridden for long periods.3 The female urethra is more prone to bacterial infections because of its short length and proximity to the anus. Chronic constipation causes bacterial overgrowth in the intestine, and this enhances the metabolism of tryptophan to indole and results in high levels of indigo and indirubin in the urine.4Therefore, PUBS is predominantly observed in chronically constipated women. PUBS treatment should be aimed at the underlying medical problem rather than the bag coloration. Purple colour can disappear spontaneously or after treatment of infection. Examination of the urine bag should draw attention to a urinary tract infection, and the phenomenon should be explained to patients. In our case, urine cultures were positive for the species Escherichia coli and Proteus mirabilis(>100,000 colonies/mL). Following treatment with ciprofloxacin for pneumonia, the patients urine bag returned to a normal colour.