A cystometry test measures how well the bladder stores and releases urine. This specialized diagnostic procedure provides healthcare providers with a detailed, objective view of bladder function, focusing on the relationship between bladder volume and pressure. As a fundamental part of urodynamic testing, it helps identify the physical and neurological causes of lower urinary tract symptoms. The information gathered is crucial for determining the most effective treatment plan for various bladder issues.
When a Cystometry Test Is Needed
A physician recommends cystometry when a patient has symptoms of poor bladder function that have not responded to initial treatments. The test distinguishes between underlying issues, such as a problem with the bladder muscle versus a blockage in the urinary tract. Common indications include urinary incontinence, such as stress incontinence and urge incontinence.
Patients experiencing frequent urination, difficulty starting a stream, or the feeling of incomplete emptying may also undergo this test. Cystometry is also used to assess neurogenic bladder dysfunction, which is often seen in individuals with conditions affecting the nervous system, such as multiple sclerosis, spinal cord injury, or diabetes-related nerve damage. By quantifying bladder capacity, muscle activity, and pressure, the test offers insights into the control of urination.
How to Prepare for the Test
Preparation for a cystometry test is straightforward but requires following specific instructions to ensure accurate results. You may be asked to arrive with a partially full or comfortably full bladder, as the initial step involves measuring your ability to empty your bladder naturally. Fasting or adjusting your normal diet before the procedure is generally not necessary.
You must discuss all current medications, including over-the-counter drugs and supplements, with your healthcare provider, as some may need to be temporarily stopped if they affect bladder function. If a urinary tract infection (UTI) is suspected, the test cannot be performed, and you may be asked to take a preventative antibiotic beforehand. Wearing comfortable, two-piece clothing is recommended, as you may need to remove clothing from the waist down and put on a gown.
The Cystometry Procedure Explained
The cystometry procedure begins after you have performed an initial voiding into a specialized toilet, which measures the rate and volume of urine flow. You will then lie down on an examination table, and a thin, flexible catheter is inserted through the urethra into the bladder. This catheter measures the amount of urine remaining in the bladder after emptying.
A second, smaller catheter or pressure probe is placed into the rectum or vagina to monitor abdominal pressure. The pressure inside the bladder is the intravesical pressure, and the pressure in the abdomen is the intra-abdominal pressure. Subtracting the abdominal pressure from the bladder pressure calculates the detrusor pressure, which is the true pressure generated by the bladder muscle.
The bladder is then slowly filled with a warm, sterile fluid, usually saline, through the catheter at a controlled rate. Monitoring equipment continuously records pressure changes as the bladder fills. During this filling phase, you report specific sensations, such as the first urge to urinate, a normal urge, and when you can no longer comfortably hold the fluid. You may also be asked to cough or strain at various volumes to check for involuntary urine leakage.
What the Results Reveal About Bladder Function
The interpretation of cystometry results focuses on how the pressure and volume graphs correlate with your reported sensations. The rate at which detrusor pressure rises during filling determines bladder compliance, which measures the bladder wall’s elasticity and ability to accommodate increasing volumes. A healthy bladder maintains a low, stable pressure as it fills.
A rapid increase in detrusor pressure during the filling phase is a sign of detrusor overactivity, a common cause of urge incontinence. The test also determines the bladder’s functional capacity, which is the maximum volume it can hold before the strong urge to void occurs. Additionally, the results help diagnose bladder outlet obstruction, indicated by a high detrusor pressure needed to achieve a low urinary flow rate during the final voiding phase.
After the catheters are removed, you may experience a mild burning sensation or a temporary increase in urinary frequency. To minimize the risk of a urinary tract infection, you are encouraged to drink extra fluids over the next 24 hours. The data collected provides the physician with the information needed to accurately diagnose the cause of your symptoms and formulate an appropriate treatment strategy.