The prognostic value of bladder contractility in transurethral resection of the prostate.

The contractility of the bladder as quantified by a parameter of approximated power per bladder surface area based on the Hill equation (Wmax) was calculated for 29 patients before and 3 months after transurethral resection of the prostate. There was no significant change in this parameter as a result of the operation. Patients who still had a significant amount of residual urine postoperatively had decreased contractility before and after surgery so that the postoperative condition could have been predicted preoperatively. In many patients a fading contraction was observed, that is detrusor contractility decreased during voiding, which gave rise to a significantly increased volume of residual urine. In most patients this pattern was restored to normal after relief of the obstruction, indicating that it was not related to structural changes in the detrusor muscle. A preoperative fading contraction had no predictive value towards the outcome of the operation.