[Clinical characteristics in patients with purple urine bag syndrome]

Purple urine bag syndrome (PUBS) occurs predominantly in chronically catheterized and constipated patients. This syndrome is associated with bacterial urinary tract infections that produce sulfatase or phosphatase. Tryptophan is converted to indole and indigo-producing bacteria have indoxyl phosphatase or sulfatase that can produce indigo (blue) and/or indirubin (red) in patients with urinary tract infection. To further explore the metabolism of these amino acids, we evaluated the serum levels of amino acids in patients with PUBS. A total of 15 patients were enrolled in this case-control study (PUBS-positive case group: 5 patients, PUBS-negative control group: 10 patients). Data from urine tests (pH, sugar, protein, leukocyte counts), renal functions (BUN, creatinine), serum levels of amino acids, and performance status were compared between the two groups. No significant differences were seen between the two groups in urine sugar, protein, leukocyte counts, renal functions, and performance status. The mean urine pH was significantly higher in PUBS patients than in control patients (8.5+/-0.0 vs. 7.3+/-1.16, respectively, p=0.0321), and serum levels of alpha-aminobutyric acid were significantly higher in PUBS patients than in control patients (16.2+/-3.08 vs. 12.4+/-3.20, respectively, p=0.0275). These data suggest that strong alkaline urine acts as an important factor in PUBS, in combination with other facilitating factors.