PA with Urodynamics Equipment Urodynamics is the study of bladder function as it relates to control (continence) and urination or voiding. This evaluation can be performed on both men and women through the use of small catheters and electrodes. Sometimes, x-rays are taken during this study (video urodynamics). The equipment used by this practice is manufactured by Life-Tech, Inc.
	CMG
	The CYSTOMETROGRAM is basically performed to evaluate the COMPLIANCE and STABILITY of the detrusor muscle. 85% of all incontinence occurs in women, and 75% of that is stress incontinence (i.e., LEAKAGE IN THE ABSENCE OF OVERACTIVITY). COMPLIANCE is simply the elastic property of the DETRUSOR muscles. An evaluation of COMPLIANCE is an evaluation of the ability of the bladder to "stretch" to "normal" capacity while maintaining low pressures. STABILITY is evaluated by observing the DETRUSOR while filling the bladder to normal capacity. The evaluation determines the presence or absence of DETRUSOR OVERACTIVITY (or INSTABILITY). A CMG evaluation routinely involves two pressure measurements and 1 subtracted pressure, with which detrusor activity is evaluated. Urethral pressure a subtracted urethral closure pressure may also be added for certain specialized studies. *SUBTRACTED PRESSURES are calculated in an effort to evaluate the pressures generated by specified structures. VESICAL PRESSURE (pves) is the pressure that is measured inside the bladder, with a catheter that was specifically designed for pressure monitoring in the urinary tract. The pressure information obtained is a combination of the pressure being exerted on the bladder by the abdominal contents, the weight or pressure of any urine in the bladder and the force that the detrusor muscle is exerting on that fluid. The pressure in an empty bladder is usually called RESTING PRESSURE. Resting pressure changes with position. The normal bladder resting pressures may vary between 8 and 40 cmH2O, depending upon the particular patient and position during study. ABDOMINAL PRESSURE (pabd) is measured by placing a special catheter either in the rectum or the vagina. Abdominal pressure information is significant because the bladder is contained in the floor of the abdominal cavity and it is important to isolate pressures and activities occurring in the bladder itself. The DETRUSOR PRESSURE is a subtracted pressure that is calculated by subtracting the abdominal pressure from the vesical pressure. A detrusor pressure channel will display a waveform tracing that represents the actual activities taking place in the bladder during the CMG. Artifact from abdominal straining, gas and the weight of the abdominal contents are removed from the information being processed from the catheter in the bladder. The ability to provide this calculated information is one of the many benefits of using digital urodynamic equipment. The dynamics of the urinary tract structures are readily illustrated when looking at the pressures in the various "chambers." This is particularly important in the female patient because relaxation of the pelvic floor and subsequent displacement of the bladder and urethra is the leading cause of stress incontinence. Illustrated below are the dynamics of the intra-abdominal cavity during a cough in a patient with a normal pelvic floor and then a relaxed pelvic floor. When the bladder is properly positioned in the abdominal cavity, both it and the bladder neck are above the pelvic floor. As illustrated below, during a valsalva (either abdominal straining or cough), the intra-abdominal pressure rises. This rise is reflected into the vesical pressure. If the bladder is properly suspended, the increased intra-abdominal pressure is also reflected in the urethra. For a patient to remain dry, the pressures in the urethra must remain greater than the pressure in the bladder, during filling. The average URETHRAL CLOSURE PRESSURE for a female is 60 cmH20 and for a male it is 80 cmH20. With aging, or after childbearing, the female pelvic floor can relax, causing the base of the bladder and the bladder neck to fall below the pelvic floor. A valsalva will usually lead to pressures in the bladder being higher than in the urethra. The result of this is stress incontinence, which is illustrated to the left. Surgical procedures can be used to raise the bladder and urethra. These suspensory procedures are typically successful, however, occasionally result in complications. Those include a permanently open bladder neck with complete incontinence or worsened incontinence in the event that the problem was DETRUSOR INSTABILITY. Instability is readily controlled by medication. The COMPLIANCE and STABILITY of the DETRUSOR muscle are most easily visualized on a subtracted, DETRUSOR channel.. A bladder with NORMAL COMPLIANCE will demonstrate NO GREATER than 15cm H2O increase in DETRUSOR pressure as it progresses from empty to capacity during a CMG. A bladder with LOW COMPLIANCE will demonstrate an INCREASE in DETRUSOR pressure GREATER than 15cm H2O as it progresses from empty to capacity during a CMG. A poorly compliant bladder typically has a low capacity. INSTABILITY should not be confused with LOW COMPLIANCE. incontinence. A bladder with HIGH COMPLIANCE will demonstrate a MINIMAL INCREASE in DETRUSOR pressure with a capacity above normal limits. NORMAL COMPLIANCE <15cm H20 pressure increase to capacity NORMAL COMPLIANCE w/DETRUSOR OVERACTIVITY as capacity is reached NORMAL COMPLIANCE w/ DETRUSOR OVERACTIVITY Stress (cough) induced LOW COMPLIANCE pdet > 15cm H20 w/ low capacity LOW COMPLIANCE w/ DETRUSOR OVERACTIVITY Unstable contractions at capacity (~ 100cc) due to muscle hypertrophy (radiation tx) LOW COMPLIANCE Bladder does not distend normally to accommodate filling. This can be due to an infusion rate that is too fast HIGH COMPLIANCE w/ DETRUSOR OVERACTIVITY High capacity bladder w/terminal overactivity. Probably neurogenic HIGH COMPLIANCE Stable w/ large capacity HIGH INTRAVESICAL PRESSURE Associated w/ stress incontinence & obesity