Case Control Study to Investigate the Use of Urethral Pressure Profile Measurement in Children

Rationale Bladder problems in children are common resulting in incontinence and social distress.

The bladder performs two functions: storage and emptying. It has two components that act synchronously with each other and allow it to achieve this: the detrusor and the sphincter complex. The detrusor is the muscle in the wall of the bladder. The sphincter complex is a group of muscles that act on the urethra, which is the outlet of the bladder. During storage the detrusor muscle is relaxed while the sphincter complex is closed. During bladder emptying the detrusor muscle contracts while the sphincter relaxes. Abnormal function of either component will result in abnormal bladder function including lower urinary tract symptoms (including frequency urgency, incontinence, difficulty voiding) and danger to the kidneys. Specifically, abnormality of the sphincter will result in either incontinence during storage, or obstructive problems during voiding.

Establishing a bladder diagnosis in children is helped by performing a test of bladder function. In the majority of children this can be done with non-invasive assessments that include bladder diary, flow rates, flow patterns residual volume measurements and electromyogram (EMG) using skin electrodes. However, in some children non-invasive testing is not able to provide enough information and so videocystometry (VCMG), or urodynamics, are performed. These are more invasive tests. Catheters are inserted into the bladder and abdomen (usually the rectum) to measure pressures generated by the detrusor. The flow rate is measured during emptying. Combining this with x-ray fluoroscopy provides additional anatomical information. VCMG provides direct information about the detrusor. Standard VCMG in children do not currently provide direct information about the tone of the sphincter. Information about sphincter function is provided indirectly by measuring the pressures during leaking, or during voiding from analysis of flow, pressure and X-ray imaging.

The investigators believe that there is a need to develop a direct diagnostic test of sphincter function in children. The investigators have a practice where children are seen with both sphincter underactivity and overactivity. Sphincter under- activity is most commonly seen in children with abnormal bladder function as a result of neurological disease (neuropathic bladder). Sphincter incompetence can be difficult to treat in children . A diagnostic test that can better define the condition may allow better targeted treatments. Sphincter overactivity will result in a poorly emptying bladder. However poor bladder emptying can also result from detrusor underactivity. In patients with incomplete bladder emptying it can be difficult to distinguish whether the condition is as a result of underactive detrusor or overactive sphincter (e.g. dysfunctional voiding or high-tone non-relaxing sphincter type conditions). The distinction is important because the two conditions require very different treatments.

There are tests of sphincter function: