What is the lower urinary tract and how does it work?
The lower urinary tract includes the bladder and urethra. The bladder sits in the pelvis and is attached to other organs, muscles, and the pelvic bones, which hold it in place. The urethra is a tube at the bottom of the bladder that carries urine from the bladder to the outside of the body.
The lower urinary tract works by coordinating the muscles of the bladder wall with the sphincters, which are circular muscles that surround the area of the bladder that opens into the urethra. The muscles of the bladder wall relax as the bladder fills with urine. If the urinary tract is healthy, the bladder can hold up to 2 cups, or 16 ounces, of urine comfortably for 2 to 5 hours. The sphincters close tightly like rubber bands around the bladder to help keep urine from leaking. As the bladder fills, the need to urinate becomes stronger and stronger, until the bladder reaches its limit. Urination is the process of emptying the bladder. To urinate, the brain signals the bladder muscles to tighten, squeezing urine out of the bladder. At the same time, the brain signals the sphincters to relax. As the sphincters relax, urine exits the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs.
What is urodynamic testing?
Urodynamic testing is any procedure that looks at how well the bladder, sphincters, and urethra are storing and releasing urine. Most urodynamic tests focus on the bladder’s ability to hold urine and empty steadily and completely. Urodynamic tests can also show whether the bladder is having involuntary contractions that cause urine leakage. A health care provider may recommend urodynamic tests if symptoms suggest problems with the lower urinary tract. Lower urinary tract symptoms (LUTS) include:
- Urine leakage
- frequent urination
- Painful urination
- Sudden, strong urges to urinate
- Problems starting a urine stream
- Problems emptying the bladder completely
- Recurrent urinary tract infections
Urodynamic tests range from simple observation to precise measurements using sophisticated instruments. For simple observation, a health care provider may record the length of time it takes a person to produce a urinary stream, note the volume of urine produced, and record the ability or inability to stop the urine flow in midstream. For precise measurements, imaging equipment takes pictures of the bladder filling and emptying, pressure monitors record the pressures inside the bladder, and sensors record muscle and nerve activity. The health care provider will decide the type of urodynamic test based on the person’s health information, physical exam, and LUTS. The urodynamic test results help diagnose the cause and nature of a lower urinary tract problem.
Most urodynamic tests do not involve special preparations, though some tests may require a person to make a change in fluid intake or to stop taking certain medications. Depending on the test, a person may be instructed to arrive for testing with a full bladder.