Purple urine bags: a geriatric presentation of lower urinary tract infection.

Abstract

To the Editor: Unusually colored urine, primarily red urine, may be associated with a disease (e.g., hematuria, myoglobinuria, porphyria) or it may be secondary to drugs side effects (e.g., Rifampin, Metronidazole). Purple colored urine in patients with indwelling urinary catheters is uncommon and has been called Purple Urine Bag Syndrome (PUBS).1 This clinical condition is a result of impaired tryptophan metabolism. We report here three new cases of PUBS and discuss the relationship between PUBS and lower urinary tract infection. In three patients catheterized because of difficulty voiding urine, purple colored urine occurred suddenly in both the catheter and the drainage bag (MONO-FLO®-Kendall Laboratory). Urinary sediment analysis showed pyuria and isolated pathogen microorganisms (Table 1). Symptoms resolved promptly after the catheter and drainage bag were removed and, in one patient, a short course of antibiotics. The PUBS diagnosis in these observations seems probable for several reasons: Purple discoloration of the urine and the plastic urinary drainage device occurred without any metabolic cause or drugs consumption such as methylene blue, Mitoxantrone, Amrinone, or Propofol Urinary discoloration, alkaline urine, and urinary tract infection — all conditions that have previously been reported in this syndrome — were associated with these patients Symptoms resolved fully after the removal of the urinary catheter and treatment for infection in one patient, These cases are similar to previously reported observations1–5 Purple discoloration of the urine is a result of (1) intestinal indole production from bacterial tryptophan catabolism absorbed into the portal circulation; (2) conjugation of indole by the liver into indoxyl-sulfate, which is excreted secondarily into urine; (3) transformation of urinary indoxyl- sulfate to indoxyl by bacterial enzymes produced by bacteria such as enterobacteria; and (4) production of indigo (blue) or indirubin (purple) pigments as a result of the oxidation of two free indoxyl molecules in the alkaline environment of the collecting bag. Clinical conditions associated with PUBS are a result of either tryptophan metabolism impairment (isolated tryptophan malabsorption or Blue Diaper Syndrome,6 Hartnup's disease7) or, more often, from lower urinary infection, as observed in our cases. Many bacteria (e.g., Providencia stuartii, Klebsiella pneumoniae, Enterobacter agglomerans) can result in indigo from indoxyl-sulfate in an alkaline environment. Alkaline urine may occur during urinary infection because of bacteria urease production.4 Thus, PUBS is found frequently in older people because of the prevalence of urinary infection and indwelling urinary catheters in this population. The frequency of PUBS after 1 month of indwelling catheterization may reach 10%.5 Clinicians should be aware of the different signs or symptoms that may reveal lower urinary tract infection in older people. PUBS should be added to the list of uncommon clinical conditions for this population.