The gastrointestinal tract bacterial flora



An 83-year-old white male with past medical history of cerebrovascular

accident, urinary incontinence with indwelling Foley catheter, atrial

fibrillation, hyperlipidemia, systolic cardiomyopathy was brought by

family for purple discoloration of Foley tubing and urinary bag for last 2

days (Figure 1). Patient complained of malaise and mild constipation. He

had no history of trauma to the catheter. He denied fever, chills or dysuria.

Physical examination was unremarkable with no suprapubic tenderness


Change of Foley catheter and treatment of underlying urinary tract infection form the mainstay of treatment of Purple Urine Bag Syndrome (PUBS). It is an interesting but unusual presentation of UTI [1,2]. Proposed risk factors include old age, chronic indwelling Foley catheter, high bacterial load in the urinary tract, an alkaline urine environment, constipation, female gender, renal failure and a diet rich in tryptophan. The gastrointestinal tract bacterial flora deaminates dietary tryptophan to produce indole. Indole undergoes hepatic conjugation to indoxyl sulphate. This is secreted into urine where bacterial enzymes convert it to indoxyl. In alkaline urine, indoxyl is oxidized to indigo (a blue pigment) and indirubin (a red pigment). These pigments combine causing striking purple staining of the catheter tubing and urinary bag [1]

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