The test needs to be scheduled in a private room with no interruption or interference. The equipment comprises a specialized commode, the outflow of the commode directed to a beaker that rests on a flowmeter (Fig. 5.2). The most commonly used integrated systems of urodynamic equipment have the monitor, infusion pole, roller pump system, filling tube set, transducer pressure domes with stop cock and printer, all stacked in a single trolley (Fig. 5.3). Two catheters (Fig. 5.4) are needed for the multichannel cystometry test. Bladder catheter is twin channeled or a composite single lumen for filling and to measure intravesical pressure. The other catheter with a balloon is inserted into the rectum to record the intra-abdominal pressure. It may also be inserted into the vagina or a colostomy stoma. The catheters are connected to pressure transducers which are in turn connected to the computer with integrated software and printer. A peristaltic pump system helps to fill the bladder with normal saline, at a predetermined rate.

The sequence of testing in urodynamics starts with the noninvasive uroflowmetry, followed by measurement of the post-void residual urine volume and then filling and voiding cystometry.

Cystometry can be either single-channel cystometry or multichannel cystometry. In single-channel cystometry, the bladder is emptied by a transurethral catheter. A 60 ml catheter tip syringe without piston is attached to the catheter and held about 15 cm above the pubic symphysis. The patient is in sitting or standing position. The bladder is filled in 50 ml increments with sterile saline or water. The volume at which patient experiences the first sensation, first desire to void, strong desire and maximum bladder capacity is noted. The meniscus of the fluid in the syringe is observed continuously and any increase signifies detrusor contraction. Multichannel cystometry has largely replaced the single-channel technique currently.

In multichannel cystometry, the patient is requested to lie down on an examination couch and the bladder and rectal lines are inserted. Residual urine if any is noted at this time. The pressure measurement lines are connected to the transducers and flushed with normal saline. All systems are zeroed at atmospheric pressure. The reference point for external transducers is the superior edge of the symphysis pubis. The patient is asked to cough to ensure an adequate rise from baseline of both pressure lines. The pressure measurement from the bladder is termed P _ves or vesical pressure and the abdominal pressure or P _abd is recorded from the rectal line.

Filling cystometry is a measurement of the pressure/volume relationship during bladder filling. It is performed using measurements of intravesical pressure (P _ves) and intra-abdominal pressure (P _abd) to calculate the detrusor pressure (P _det = P _ves – P _abd). The key features of bladder storage function obtained with filling cystometry include bladder sensation, cystometric bladder capacity, compliance and presence of involuntary detrusor contractions or detrusor overactivity (DO). The aim is to replicate the woman’s symptoms by filling the bladder and observing pressure changes or leakage caused by provocation tests.