Purple urine bag syndrome is most commonly associated with which condition?

• A. Urinary tract infection in a patient with a long-term indwelling urinary catheter
• B. Dehydration
• C. Urinary retention without catheter
• D. Acute pyelonephritis

Answer: (A)

Purple urine bag syndrome happens when a person with a long-term indwelling urinary catheter develops a urinary tract infection. In this situation, certain bacteria that colonize the catheter produce enzymes (sulfatases and phosphatases) that convert tryptophan metabolites in the urine into indigo and indirubin pigments. When these pigments mix in the urine bag, the bag or urine takes on a purple color. The key factor is the combination of a chronic catheter and a urinary infection, which creates the environment for pigment formation. Other scenarios like dehydration, urinary retention without a catheter, or acute pyelonephritis do not commonly produce this pigment phenomenon in the urine bag.