Relationship between Urine Ph and in Vivo Atp Release during Urodynamic Tests in Female Urinary Incontinence

Study design, materials and methods Informed consent was obtained and the study was approved by local human ethics committee. A midstream urine sample was collected for pH measurement immediately before the routine urodynamic test was performed. These samples were also tested for bacteriuria, and subjects found to have bacterial cystitis on the test day (10 7 c.f.u / L with pyuria >10 wbc / L) were excluded from the study. Urine pH measurements were promptly carried out on fresh urine samples (mean +/SEM). During the urodymamic test, sterile saline was infused into the bladder at a filling rate of 75mL/min. The volumes at first desire to void (FDV) and maximum cystometry capacity (MCC) were noted. The voided urodynamic fluid was collected for ATP determinations. Patients were characterised as DO (involuntary detrusor contractions during the filling phase which may be spontaneous or provoked), bladder oversensitivity (BO, with FDV ≤ 200mL and MCC ≤ 400mL but with stable bladder) or control (neither DO or BO, i.e. pure urodynamic stress incontinence, involuntary leakage of urine during increased abdominal pressure in the absence of detrusor contractions). Overall subject numbers (age range 28-87 years) comprised 90 DO, 24 BO and 74 controls (22 patients with bacteriuria on the test day were excluded). The urine and voided urodynamic fluid were frozen at -20 o C. ATP determinations were carried out on thawed urine and voided urodynamic fluid. ATP was measured using a bioluminescence assay (Sigma) and a luminometer (GloMax 20/20). In uninfected patients there is no difference in ATP measurement in fresh or frozen samples. The concentration of ATP (nmoles/L) in the bladder washing in each sample was calculated, and data were expressed as median (interquartile range, IQR). Correlations between two factors were tested by linear regression analysis. The three subject groups were compared using the Kruskal-Wallis test.