| Cystometry | |
|---|---|
 Example cystometrogram. | |
| ICD-9-CM | 89.22 |
Cystometry, also known asflow cystometry, is a clinical diagnostic procedure used to evaluate bladder function. Specifically, it measures contractile force of thebladder whenvoiding. The resulting chart generated from cystometric analysis is known as acystometrogram (CMG), which plots intravesical pressure against the volume of fluid in the bladder.[1][2]
Cystometric analysis is used to evaluate the bladder's capacity to contract and expel urine. It helps determine the source of urinary problems. A normal CMG effectively rules out primary vesical dysfunction. It is used as a component for diagnosis of various disorders includingurinary tract infections,multiple sclerosis,stroke,spinal cord injury,urethral obstruction, andoveractive bladder, among others.[3]
The procedure is relatively short, ranging from fifteen minutes[4] to an hour in duration.[5] It involves the insertion of one or twocatheters into an emptied bladder through the urethra. In the two catheter method, one catheter transfers liquid while the other is amanometer (pressure sensor).[6] In the single catheter method, a specialized catheter performs both functions. An additional rectal catheter may also be placed for additional data. The bladder will then be filled withsaline and the patient's awareness of the event will be queried. The patient will often be asked to note when presence of liquid is felt, when the bladder feels full, and when the urgency to void is felt. The patient is then asked to void, and both flow and pressure are recorded.[5] These are plotted against each other to create the cystometrogram.
The primary results of cystometric analysis is the cystometrogram. Thex-axis is the volume of liquid and they-axis is the intraluminal pressure of the bladder. In normal patients, the plot is a series of spikes whose local minimums form anon-linear curve resembling anexponential growth curve. The spikes correspond to the bladder contractions associated with themicturition reflex. The curve formed by the bottom of the plot reflects the level of pressure necessary to void. In normal patients, the first couple hundredmilliliters of urine flow with minimal applied pressure. Increasing pressure is necessary to void 200 to 300 milliliters of urine. Beyond that, the pressure necessary to void additional urine rises sharply.[7]
As with any catheterization, the primary risk is of urinary tract infection. As a result, the procedure is contraindicated in any patient with an active UTI because the results may be skewed and the infection may spread[citation needed].
There is also the potential for trauma to the bladder and urethra, which may result inhematuria (blood in the urine).[3]
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