New method to quantify the urodynamic improvement when treating bladder outlet obstruction: the efficacy of...

A method to measure the urodynamic improvement when treating urethral obstruction is introduced and applied to patients with benign prostatic hypertrophy. The patients performed pressure-flow studies before and 3-6 months after TUR-p. The urethral resistance relation was estimated by curve fitting in the pressure flow plot. The new method quantifies the improvement in urethral resistance as the distance between the urethral resistance relation before and after treatment expressed in pressure units. The distance is measured at the flow rate equal to 75% of the maximum flow rate for the micturition with the lowest maximum flow rate and this distance is called delta-URA. The median improvement after TUR-p was 71 cm H2O (range 2-119). The improvement was strongly correlated to the resistance before treatment and the regression line indicates that the operation normalizes the resistance irrespective of its preoperative value. On the average a lowering of the urethral resistance relation with 8 cm H2O improved the maximum flow rate with 1 ml/s. The greatest advantage with the new method is that it has a high validity and is almost completely insensitive to changes in contractility.