[Serum levels of amino acid in patients with purple urine bag syndrome].

The plastic of urinary catheter drainage bags occasionally turns purple hours or days after catheterization and the color becomes increasingly intense the longer the same drainage system is left in place. This phenomenon was first reported in 1978 as "purple urine bag syndrome", and had been known to occur with bacterial infection of the urinary tract with chronic constipation. Chronic constipation is commonly associated with bacterial overgrowth in the bowel in which tryptophan has been converted to indol and yields the high levels of indigo (blue) and indirubin (red) in urinary bags of patients with bacterial infection of the urine, because indigo-producing bacteria have indoxyl phosphatase or sulfatase that can produce indigo and indirubin. We determined the serum levels of amino acids in patients with purple urine bag syndrome. The serum level of tryptophan and valine were significantly reduced in patients with purple urine bag syndrome. This result suggests that absorption of amino acids was affected by disturbances of colonic motility and intestinal bacterial overgrowth.