10. Cystometrogram

a. Measures changes in bladder pressure with increases in bladder volume; evaluates the bladder’s ability to fill uniformly and store

urine, by assessing detrusor activity, sensation, capacity, and compliance

b. Definitions4

(1) Intravesical pressure: the pressure within the bladder

(2) Abdominal pressure: the pressure surrounding the bladder

(3) Detrusor pressure: a measure of the passive and active forces within the bladder wall, obtained by subtracting abdominal pressure from intravesical pressure

(4) Bladder sensation: subjective; involves the following:

(a) First desire to void

(b) Normal desire to void: feeling that leads the patient to pass urine at the next convenient moment (can be delayed or postponed)

(c) Strong desire to void: persistent desire to void without fear of leakage or pain

(d) Urgency: the strong desire to void accompanied by fear of leakage and pain

11. Three phases of bladder filling.

a. The compliance phase is composed of the following:

(1) An initial rise in pressure to achieve resting bladder pressure

(2) A tonus limb that reflects the bladder’s viscoelastic response to accommodating filling

(a) Bladder compliance: the change in detrusor pressure that accompanies an increase in bladder volume during filling; not to exceed 15 cm of water. Compliance depends on the following:

(i) Rate of filling

(ii) The volume interval over which compliance is calculated

(iii) Bladder wall thickness

(iv) Mechanical bladder wall properties

(v) Shape of the bladder

(vi) Contractile and relaxant properties of the bladder wall

b. The contraction phase characterizations

(1) A rapid rise in intravesical pressure

(2) Ability of patient to suppress voluntary voiding contractions


c. The voiding phase

(1) Requires an intact neural pathway to the brainstem micturition center

(2) Coordination of the detrusor contraction with concomitant relaxation of the sphincter results in voiding

d. Gas cystometry1

(1) Clean and efficient

(2) Allows rapid filling of the bladder

(3) Impairs accommodation, producing a low-volume total capacity

(4) Irritating to the urothelium, producing discomfort and dysuria

(5) Gas compressibiliM.may mask low-amplitude phasic contractions and blunt high-pressure contractions

(6) Gas can leak

e. Other terminology

(1) Involuntary detrusor contraction: a phasic rise, uninhibited, in bladder pressure, generally provoked fey a stimulus, which signifies a lack of accommodation on the part of the bladder during filling; pressures exceed 15 cm of water

(2) Two phases of voluntary control

(a) The ability to initiate a bladder contraction

(b) The ability 8b inhibit the bladder contraction.)

(3) Maximum functional capacity: the largest amount voided at any one time over a 24-hout observation period

(4) Maximal cystometric capacity: the volume at which the patient feels micturition can no longer be delayed



Normal perfusion urethral pressure profile.

 Normal perfusion urethral pressure profile.

Table 1. Dynamic Changes Seen with Urethral Pressure Profiles: Dynamic Function of the Urethral Sphincteric Mechanism in Normal Women and in Patients with Genuine Stress Incontinence

Changes with Closure Pressure Response
Urethral Closure
Pressure Profile Stress
in Response to Normal Incontinent
the Following Patient Patient
Cough Increased Minimal to none
Valsalva Increased Minimal to none
Holding urine Increased Minimal to none
Contraction of perineal muscles Increased Minimal to none
Bladder distension*
Partially full Increase Minimal to none
Full distension Further increase Minimal to none
Sitting Increase Minimal to none
Standing Further increase Minimal to none



Normal adult cystometrogram

Normal adult cystometrogram. I, The compliance phase; II, the contraction phase; III, the voiding phase.





Various representative adult cystometrograms

Various representative adult cystometrograms. A, Normal filling curve in a patient with a bladder capacity of 450 mL, normal compliance, and no involuntary bladder contractions. Nothing can be said about bladder activity during the emptying phase of micturition from this tracing. B, Large-capacity bladder with increased compliance at medium fill rate. This type of curve is characteristic of an individual with decreased sensation and bladder decompensation. Although most individuals will in fact have no or poor detrusor contraction, that conclusion cannot be made on the basis of this curve. C, Decreased compliance. D, Small-capacity bladder secondary to hypersensitivity without decreased compliance or involuntary bladder contraction. E, Bladder contraction provoked by cough. This particular tracing represents total bladder pressure. To make this diagnosis from just this tracing would require either a very astute examiner or separate recordings of intravesical pressure and intraabdominal pressure (intrarectal pressure). F, Low-amplitude detrusor contractions. This is a subtracted bladder pressure, and this type of recording may be seen most characteristically in a patient with suprasacral neurologic disease or idiopathic detrusor instability. G, Decreased compliance and involuntary bladder contractions. H, High-amplitude early involuntary bladder contraction.

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