Background: Work in voiding (WIV) of the bladder may be used to evaluate bladder status throughout urination, not just at a single time point. Few studies, however, have assessed WIV due to the complexity of the calculations. We have developed a method of calculating work capacity of the bladder while voiding and analyzed the associations of bladder work parameters with bladder contractile function and bladder outlet obstruction (BOO).
Methods: The study retrospectively evaluated 160 males, aged >40 years and with a detrusor pressure at maximal flow rate (PdetQmax) of ≥40 cmH2O, who underwent urodynamic testing. WIV was calculated using the bladder power integration method; WIV per second (WIV/t) and WIV per liter urine voided (WIV/v) were also calculated. The relationships between these work capacity parameters and PdetQmax and AG number were determined using linear-by-linear association tests, and relationships between work capacity parameters and BOO grade were investigated using Spearman’s association test.
Results: Mean WIV was 1.15±0.78 J, mean WIV/t was 22.95±14.45 milliWatt, and mean WIV/v was 5.59±2.32 J/L. WIV/v showed significant positive associations with PdetQmax (r=0.845, P=0.000), AG number (r=0.814, P=0.000), and Schafer class (r=0.726, P=0.000). Conversely, WIV and WIV/t showed no associations with PdetQmax or AG number. In patients with BOO (Schafer class > II), WIV/v correlated positively with increasing BOO grade.
Conclusions: WIV can be calculated from simple urodynamic parameters using the bladder power integration method. WIV/v may be a marker of both bladder contractile function and BOO.
