A 91-year-old was male presented to the emergency department following a fall from a chair. He was unable to identify any significant symptoms preceding the fall. He sustained no significant injuries and basic physiological observations were within normal limits. Past medical history revealed he was known to have a long-term catheter (LTC) for benign prostate hyperplasia (BPH). The only notable finding on initial investigations was moderately elevated inflammatory markers. He was admitted under the medical team for further assessment. On re-examination his urine appeared to have a purple discoloration in the leg bag (Figure 1). His genital hygiene was poor. Microscopy, culture and sensitivity of the catheter urine sample grew heavy mixed bacterial growth.

The patient made a full recovery following empirical intravenous broad-spectrum antibiotics then focused oral antibiotics in accordance with the sensitivities. This was combined with replacement of the LTC under aseptic non-touch technique.

Purple bag syndrome (PBS), also known as purple urine bag syndrome (PUBS), is a reasonably rare syndrome [1] of urinary tract infection associated with several bacterial pathogens [2][3].

Providencia stuartii, Providencia rettgeri, Klebsiella pneumoniae, Proteus mirabilis, Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa have all been linked to purple bag syndrome. It is believed that the purple color is created through a metabolic cascade that begins with tryptophan in food reacting with gut bacteria. Through the portal circulation and interaction with alkaline urine, there is production of the red indirubin and blue indigo pigments. The two react with the polyvinyl chloride of the catheter bag and produce the purple coloration [1][2][3].

Purple bag syndrome appears alarming. It can range from being an innocuous incidental finding to representing significant urinary tract infection and even a precursor to urosepsis. Clinical correlation must be made. Treatment however is no different to other catheter associated urinary tract infections– suitable antimicrobial therapy should be administered in accordance with relevant microbiology results and the catheter replaced.

1. Su FH, Chung SY, Chen MH, et al. Case analysis of purple urine-bag syndrome at a long-term care service in a community hospital. Chang Gung Med J 2005 Sep;28(9):636–42.   [Pubmed]    
2. Dealler SF, Hawkey PM, Millar MR. Enzymatic degradation of urinary indoxyl sulfate by Providencia stuartii and Klebsiella pneumoniae causes the purple urine bag syndrome. J Clin Microbiol 1988 Oct;26(10):2152–6.   [Pubmed]    
3. Matsuo H, Ishibashi T, Araki C, et al. Report of three cases of purple urine bag syndrome which occurred with a combination of both E. coli and M. morganii. [Article in Japanese]. Kansenshogaku Zasshi 1993 May;67(5):487–90.   [CrossRef]   [Pubmed]