Pitfalls in determination of leak point pressure.

To evaluate the influence of the technical aspects of leak point pressure measurement we performed water cystometry and determined the leak point pressure in 23 patients 5 weeks to 21 years old with neurogenic bladders. We initially assessed the influence of catheter size on the leak point pressure and determined that the measured pressure varied in direct proportion to the catheter diameter. We further evaluated the effect of the method of infusion (gravity drip versus pump) and the infusion rate on pressures measured by a transducer in an in vitro setting. Using the gravity drip infusion technique pressure measurement was adversely affected by smaller catheter size and rapid infusion rate. With the pump infusion system neither catheter size nor infusion rate adversely affected pressure measurement. We conclude that the clinical measurement of the leak point pressure during water cystometry is influenced by the catheter size, and it is dependent upon the technique and rate of infusion. We believe that standardization of the technical aspects of leak point pressure determination would provide for reproducible results and facilitate comparisons of reports among different investigators.