[Bladder wall tension with physiological bladder emptying in patients with detrusor hyperactivity and infravesical...

The range of maximum bladder smooth muscle tension in the published literature varies between 1.3 and 59 N/cm (2) depending on the experimental setup. Based on own animal trials, we attempted to determine bladder wall tension during detrusor contraction in physiological and obstructed voiding and during detrusor instabilities in our patient collective.

In 24 patients (mean age 56 +/- 8.4 years), bladder wall tension as detrusor force per cross sectional area of bladder tissue [in N/cm (2)] was calculated following urodynamic evaluation and ultrasound determination of bladder wall thickness. The patients were divided into 3 groups with 8 patients per group as follows: group I: patients with bladder outlet obstruction in accordance with the Abrams-Griffiths nomogramme; group II: patients with detrusor instabilities; group III: patients with normal bladder emptying.

Maximum bladder wall tension in group I was 9.8 +/- 3.9 N/cm (2). During bladder instabilities (group II), maximum bladder wall tension was 11.7 +/- 2.6 N/cm (2). Maximum bladder wall tension was 2.8 +/- 0.5 N/cm (2) in group III, which was significantly lower (p < 0.05, Mann-Whitney U-Test) than that of groups I and II.

We conclude that bladder wall tension is distinctly lower in patients with normal voiding than in those with obstructed micturition or detrusor instabilities. Furthermore, our results suggest that the detrusor is not fully activated during normal voiding and is thus capable of compensating for to a greater stress situation with more effective contractions.