What is a cystometry test?

Jill Rabin
OBGYN (Obstetrics & Gynecology)

Cystometry is the measurement of the pressure and volume of the bladder both when full and when emptying. The cystometer, the machine that performs this urodynamic test, produces a graph called a cystometrogram.

Cystometry is used to determine whether incontinence is the result of involuntary bladder contractions (urge incontinence or detrusor instability), weak pelvic muscles or urethral sphincter (stress incontinence), or both (mixed incontinence) and whether there is pain or discomfort when the bladder fills or empties.

A video urodynamic test, or VUDS (cystometry used in conjunction with X-ray imaging to evaluate and examine the position of the bladder neck when leakage occurs during exertion) is very helpful for women who have undergone surgery or who have complicated problems. While it may be the most precise method for determining and classifying stress urinary incontinence, it requires X-ray equipment and facilities with lead-lined rooms. These are not always readily available.

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Cystometry, which can be part of urodynamic testing for urinary problems, monitors how the pressure builds up in your bladder as it fills with urine, how much urine your bladder can hold, and at what point you feel the urge to urinate.

During cystometry, a very narrow catheter is placed in your bladder to measure pressure. Through the catheter, the technician slowly fills your bladder with sterile water. The catheter measures the pressure inside your bladder and can measure the pressure inside the urethra; an additional small pressure catheter may also be inserted into your rectum (for men) or vaginal canal (for women). You tell the physician when you first feel the urge to urinate, when the urge becomes strong, and other sensations (pain, temperature changes, and the symptoms that brought you to the doctor).

This test detects abnormal contractions or spasms of your detrusor muscle during filling, indicating incontinence caused by an overactive bladder (either alone or along with stress incontinence). At several points during the filling, you may be asked to cough or bear down so the doctor can see whether fluid comes out of the urethra. This measurement is sometimes called leak point pressure.

A low leak point pressure is a sign of stress incontinence. If it is extremely low (you start to leak as soon as you begin bearing down), it may mean that age-related changes or scar tissue is preventing your urethra from closing well enough to prevent urine leakage, resulting in the type of stress incontinence called intrinsic sphincter deficiency.

Once your bladder is filled to the point where you have a strong urge, you will urinate, and the pressure and volume are measured. By monitoring pressure while you urinate, this test can distinguish whether a low flow is due to weak bladder contractions or something blocking the flow. Portions of the test may be repeated while you are in a standing position, which makes stress incontinence more apparent.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.