Flow time: time over which measurable flow occurs
Time to maximum flow: time elapsed from the onset of flow to maximum rate
Maximum flow rate: the maximal rate of flow
Voided volume: the total volume expelled by way of the urethra
Average flow rate: the voided volume divided by flow time
Voiding time: the total duration of micturition, including interruptions
Flow pattern: may be continuous, interrupted, or specifically described
8. Uroflow studies: defined as the volume of fluid expelled from the urethra per unit time expressed in mL/s.3 It expresses the combined activity of the detrusor and urethra. Box 4*2 lists the terminology of the International Continence Society relating to the urodynamic description of urinary flow. The flow pattern in Figure 4-1 is normal. Minimum acceptable urine flow rates are listed in Table 4-3. Volumes under 150 cc should be interpreted with caution.
9. Urethral pressure profile
a. Allows for the measurement of the active and passive tone of the urethra.1
b. Measures urethral pressure with the patient lying down, the bladder at rest, and the urethra closed.
Terminology of the International Continence Society as it applies to a normal flow pattern.
Data from Abrams P: The urethral pressure profile measurement.
c. Uses a specially designed catheter with multiple side holes and an occluded tip. (Fluid infused along the catheter escapes through the side holes and the urethral pressure profile measures the resistance of the urethral walls to distension by the escaping
d. Nomenclature for the urethral pressure profile.
(1) Maximum urethral pressure: the maximum pressure of the profile
(2) Maximum urethral closing pressure: the difference between the maximum urethral pressure and bladder pressure
(3) Functional profile length: the length of the urethra along which the pressure exceeds bladder pressure
(4) Total urethral length: functional length plus the additional length to reach atmospheric pressure
e. Types of urethral pressure profile.
(1) Static: measures urethral pressure with the patient lying down, the bladder at rest, and the urethra closed.
(2) Perfusion: using saline or gas perfusion through a motorized syringe pump.
(3) Stress: while the catheter is withdrawn from the bladder through the urethra at a rate of 0.1 cm/s, the patient is asked to cough. In patients with genuine stress urinary incontinence, there is a failure of pressure transmission to the proximal two thirds of the urethra. Normal patients demonstrate intraabdominal pressure transmission to the proximal two thirds of the urethra.
(4) Dynamic: shows variation in sphincteric closure pressure under various physiologic events, various stresses, and various commands (Table 4-4). It uses the membrane catheter or microtransducer technique.
f. Figure 4-2 shows a normal perfusion urethral pressure profile.