If your condition is not easily diagnosed by a physical exam and a discussion of your symptoms, or if previous treatments have not improved your symptoms of incontinence, your doctor may suggest urodynamic testing, a series of specialized tests that help evaluate your urinary system in action. Many doctors who diagnose patients with urinary problems have a urodynamic testing lab outfitted with a special chair and computer equipment that can help obtain measurements of urinary pressure and flow.
Urodynamic testing is available for both men and women. For women, the testing may be done by a physician who is a urogynecologist, a doctor certified in this board-certified subspecialty. A technician in the doctor’s office may also perform the testing. Men should consult a urologist, another board-certified specialist.
The usefulness of urodynamic testing depends on the experience of the tester, the choice of tests, and the type of incontinence. For example, urodynamic tests are very sensitive in detecting stress incontinence, but asking patients about their symptoms is almost as good, and is even more effective when supplemented with a bladder diary.
Urodynamic testing will likely be recommended if your symptoms point toward more than one type of incontinence, if you have had previous surgery on your bladder or sphincters, if surgery is planned, or if you do not improve after standard treatments.
Your urodynamic test is likely to include one or more of the following procedures.
Figure 4: Detecting bladder problems
Before you begin urodynamic testing, your doctor will ask you to describe your symptoms and your personal health history. Once you are in the urodynamic testing lab (above), you’ll sit in a specially designed chair equipped with sensitive catheters that feed information from your bladder to a computer that records bladder volume, pressure, rate of flow, and leakage.
Photo courtesy of May M. Wakamatsu, M.D.
For this test, you start with a full bladder and urinate into a funnel at a special urinal or commode that automatically measures the amount you produce and the rate of the flow. A slow flow might indicate an obstruction in the urethra or a weak bladder muscle. This test is quick and noninvasive.
Post-void residual volume
This test measures the amount of urine left in your bladder after you urinate. Two techniques are used to measure this. The physician may insert a flexible tube (called a catheter) through your urethra into the bladder to draw off the remaining fluid (which also provides an uncontaminated sample for urine culture and prepares you for further tests). Being catheterized usually causes only mild discomfort. Alternatively, the amount of urine in your bladder can be visualized using a specialized ultrasound machine called a bladder scanner. This is quicker and more comfortable, and it avoids the possibility that inserting a catheter could cause an infection or traumatize the lining of the urethra. However, it can be less accurate.
Measuring residual urine volume is particularly valuable if you are troubled by repeated urinary tract infections, if you have a neurological disorder, or if your doctor suspects that a blockage is preventing your bladder from emptying properly.
This test 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 (see Figure 5).
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.
In women, urogynecologists often perform a test called a urethral pressure profile. The bladder/urethral catheter is drawn through the urethra very slowly, and the urethral pressure is measured. If the pressure is low, that indicates your urethral sphincter is weak, which causes stress incontinence.
Figure 5: Pressure test (Cystometry)
For men or women, a cystometry test measures the pressure in the bladder, urethra, and abdomen. A catheter in the bladder fills the bladder with fluid and measures pressure in centimeters of water. Another catheter, placed in the vagina for women or the rectum for men, reflects the pressure in the abdomen. Cystometry can reveal detrusor overactivity, stress incontinence from sphincter weakness, or weak pelvic floor muscles.
In this test, small electrode patches are placed in the crotch area to pick up electrical current that is created when the pelvic floor muscles contract. Called a surface EMG, this test may help determine whether the activities of the bladder and urethra are coordinated with each other.
If your doctor suspects that the nerves to your urinary sphincter are seriously damaged, or that the sphincter muscle is responding inappropriately to nerve signals, he or she may insert a thin needle electrode into the muscle of the urethra to perform a more accurate EMG. This test may also be performed by a neurologist. Because most people find the EMG causes some pain, it is not done routinely.
A cystogram, or voiding cystourethrogram, is an x-ray test. The test itself may be performed during cystometry or uroflowmetry, or both, but a fluid visible on x-ray is substituted for the sterile water. At various points in the process, x-rays are taken as you cough or bear down and as you urinate. This test can pinpoint the location of a blockage or reveal an abnormally open urethra.
Using highly specialized equipment, this technique combines cystometry, uroflowmetry, and cystography into a single computerized test. This equipment can simultaneously measure urine flow and pressure in the bladder and rectum. The test may provide useful information about your bladder and urethral function, especially if you have problems voiding (such as being able to begin urinating only in a certain position). The equipment for video-urodynamic testing is expensive and not widely used.
After urodynamic testing
You might have mild discomfort or soreness for a few hours after these tests. Drinking two large glasses of water each hour for two hours may help ease your symptoms. Ask your doctor whether you can take a warm bath. If not, you may be able to hold a warm, damp washcloth over the urethral opening to relieve the discomfort. Your doctor may give you an antibiotic to take for one to two days to prevent an infection. If you have signs of infection, fever, chills, or pain, call your doctor.
Results: For some of the more simple tests, you may get answers as the test is being done or right after it’s done. For others, it will take a few days.
Other evaluation procedures
Depending on your symptoms, other tests may be performed at the same visit as your urodynamic testing.
Using a lighted telescope at the end of a thin tube called a cystoscope, your doctor can inspect the inside of your urethra and bladder for signs of infection, abnormal growths, bladder stones, scarring, or improperly placed stitches from previous surgeries. This test is used in both men and women, but it is easier for women to undergo comfortably because the urethra is shorter.
For the test, you lie on your back. A numbing jelly is placed into your urethra, and the cystoscope is inserted until the end is inside your bladder. Sterile water is passed through the thin tube to fill your bladder and optimize the picture. You may feel some discomfort and the need to urinate when your bladder is filled. After about three to five minutes, the cystoscope is removed, and you can use the toilet.
Ultrasound uses sound waves rather than x-rays to create an image of internal organs. You may undergo an abdominal or transvaginal ultrasound exam to look at the structure and position of your kidneys, bladder, and prostate; to visualize leakage in stress incontinence; to detect abnormalities such as tumors, kidney stones, or fibroids; or to evaluate treatment with bulking agents (see “Injection of bulking agents”). An ultrasound exam takes about half an hour and is painless.
Intravenous pyelogram or urogram
This test creates a picture of your kidneys and ureters. A dye is injected into your bloodstream through your arm. The dye is excreted through the kidneys and collects in urine, allowing an x-ray to reveal the structure of the kidneys and ureters and any areas where fluid may be escaping or is blocked.