Purple urine bag syndrome (PUBS) is an intriguing phenomenon featured by an alarming purple discoloration of the urine and the urine bag because of the mixture of indigo (blue) and indirubin (red). It is a secondary phenomenon to bacterial urinary tract infection (UTI) with sulfatase/phosphatase producing bacteria. This situation is thought to arise from a series of biochemical steps involving the metabolism of tryptophan in the gut to indigo and indirubin pigment in the urine. While there are multiple factors associated with PUBS, it occurs particularly in chronically debilitated, constipated, catheterized, elderly female subjects in the presence of alkaline urine. We report a case of 78-year-old man of multiple myeloma with acute kidney injury and other comorbid conditions, who was admitted for gastrointestinal bleed and developed Escherichia coli-related UTI, followed by the development of PUBS. He responded to the treatment with antibiotics and change of catheter and urine bag. PUBS is harmless without any serious consequences but an uncomfortable or troubling issue for patients and their families. Most patients who present with PUBS are largely asymptomatic. Treating the underlying UTI, reassurance, change of the urinary catheter, and urinary sanitation are fundamental to its treatment.
Key words: Urinary catheter, urinary tract infection, tryptophan metabolism, indigo, indirubin pigment