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Urodynamic testing is a medical test used to observe the function of the urinary system during urination. It is used to help diagnose conditions affecting normal urination, helping the doctor pinpoint the physical cause of the problem. The test may simply involve a device to measure urine flow, or it may be more complex, involving medical imaging technology to help visualize the urinary tract.
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Background: The Urinary Tract
In the urinary tract, urine is produced in the kidneys, then flows through tubes (one for each kidney) called ureters to the urinary bladder. The bladder collects and temporarily stores urine, preventing healthy people from needing to urinate small amounts constantly. During urination, a muscle called a sphincter relaxes, causing the urine to pass through a tube called the urethra out of the body. The urethra is significantly longer in males than in females because in males, it passes along the entire length of the penis.
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Symptoms Indicating the Need For the Test
Urodynamic testing may be used to help pinpoint the cause of any of the following symptoms:
- Urinary incontinence
- Trouble starting to urinate
- Frequent urination
- Sudden, overwhelming urges to urinate
- Pain during urination
- Recurrent urinary tract infections (UTIs)
- Inability to completely void the bladder
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Types of Testing
Uroflowmetry uses a device called a uroflowmeter to measure, from moment to moment, the amount of flow in the urine stream.
A postvoid residual involves a catheter inserted into the bladder after urination to drain and measure the remaining urine. Up to an ounce or two of residual urine is considered within the normal range, but more than three ounces may indicate a problem.
Cystometry is used to determine bladder volume, and how full the bladder must be (in terms of both volume and pressure) before the patient feels the urge to urinate. It involves filling an empty bladder with measured amounts of saline solution while measuring bladder pressure with a device inserted via the rectum. Sudden leakage during this test helps doctors diagnose problems with the sphincter muscle; measurement of leak point pressure provides this important information. The cystometry test may be followed by a pressure flow study to help diagnose blockages in the urethra, which is especially common in men with enlarged prostates.
Video urodynamics uses x-ray or ultrasound imaging to visualize the process of urination.
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After the Test
Some discomfort may be experienced after the testing is completed. Drinking plenty of water to cause increased urination may help, as may a warm bath, if approved by the doctor. Because the use of urinary catheters is associated with urinary tract infections, an antibiotic may be used as prophylaxis.
A possible side effect of urodynamic testing, especially tests requiring catheterization of the bladder, is an acute urinary tract infection. Symptoms include painful urination, cloudy urine, fever, and chills. Anyone experiencing these symptoms should seek medical attention right away.
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"Urodynamic Testing." National Kidney and Urologic Disease Information Clearinghouse (U.S. National Institutes of Health).