Repeat noninvasive bladder pressure measurements with an external catheter

Previously it has been shown that an objective diagnosis of infravesical obstruction can be made by combining the maximum flow rate and isovolumetric bladder pressure. We evaluate a noninvasive method to measure isovolumetric bladder pressure to help develop a noninvasive modality for diagnosing obstruction.

An external catheter consisting of an incontinence condom, tube and pressure transducer was used. Flow rate through the catheter was remotely interrupted to measure the bladder pressure in the condom. Two series of measurements were done in 11 healthy male volunteers. In the first series we determined whether voiding was affected after flow rate interruption. In the second series we analyzed repeat pressure measurements of 1 voiding to determine whether maximum isovolumetric pressure depended on bladder volume.

Flow rate was unaffected after interruption for pressure measurement. Repeat measurements of isovolumetric bladder pressure demonstrated that the pressure depended significantly on bladder volume. Average maximum isovolumetric pressure was 12.2 kPa. at a bladder volume of 251 ml.

As no inhibition of voiding was noted after a single pressure measurement, repeat noninvasive measurements can be made on voiding. With repeat measurements the dependence of isovolumetric bladder pressure on bladder volume can be considered to obtain a reliable estimate of pressure as a basis for a noninvasive diagnosis of obstruction.