The detrusor muscles of a normal bladder will not contract during filling. Severe contractions at low amounts of administered fluid (less than 200 mL) indicate urge incontinence. If there is no significant increase in bladder pressure or detrusor muscle contractions during the process but the patient experiences leakage if abdominal pressure increases, such as during the Valsalva movement, then stress incontinence is suspected.
Video Cystometry. Video cystometry combines a computer reading of bladder pressures and pictures of the bladder itself. It is most useful in cases where the more standard tests have not yielded satisfactory results.
Uroflowmetry
To determine whether the bladder is obstructed, the speed of urine flow is measured electronically using a test called uroflowmetry. The test involves the following steps:
- Patients are instructed not to urinate for several hours before the test and to drink plenty of fluids so they have a full bladder and a strong urge to urinate.
- To perform this test, a patient urinates into a special toilet equipped with a uroflowmeter.
- It is important that patients remain still while urinating to help ensure accuracy, and that they urinate normally and do not exert strain to empty their bladder or attempt to retard their urine flow.
Many factors can affect urine flow (such as straining or holding back because of self-consciousness) so experts recommend that the test be repeated at least twice.
Q[max]. The rate of urine flow is calculated as milliliters of urine passed per second (mL/s). At its peak, the flow rate measurement is recorded and referred to as the Q[max]. The higher the Q[max], the better the patient's flow rate. Men with a Q[max] of less than 12 mL/s have four times the risk for urinary retention than men with a stronger urinary flow.
The Q[max] measurement is sometimes used as the basis for determining the severity of obstruction and for judging the success of treatments. It is not very accurate, however, for a number of reasons:
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