A case-control study of purple urine bag syndrome in geriatric wards.

The clinical background of purple urine bag syndrome (PUBS) has not yet been well characterized. In previous reports, clinical, biochemical, or bacteriological analyses were carried out using urine or bacteria from a limited number of patients. Other than one report, we are not aware of any case-control studies that compared the clinical, biochemical, or bacteriological background between patients with and without PUBS. To examine the risk of PUBS, we carried out a case-control study. Twenty-six patients, in three long-term care wards, who had been catheterized for more than 3 months with the same types of balloon catheters and who had the same type of disposable plastic urine bags were enrolled as the PUBS-positive case group (14 patients; 2 men and 12 women), and as the PUBS-negative control group (12 patients; 4 men and 8 women) were enrolled. The data for urine tests (pH, sugar, protein, leukocyte counts, and bacterial yields and species) were compared for the two groups. A relatively higher prevalence of PUBS was observed in female and alkaline-urine-producing patients. Bacteriological studies, using fresh urine collected through the catheter, showed that the bacterial counts were significantly higher, by 1 to 2 logs, in most samples from the case group than those from the control group (P = 0.012). Although a total of 66 bacterial strains, belonging to 12 separate species, were isolated from the urine accumulated in bags, no causative relationship between bacterial species and PUBS was observed. These data suggest that a higher bacterial yield in urine acts as the most important factor in PUBS, in combination with other facilitating factors, such as female-specific ones and the alkaline condition of urine.