Urodynamic Studies

Urodynamic Studies

DEFINITION

Urodynamics is the study of the changing parameters of bladder filling, storage, and emptying, dealing with the interaction of the bladder with its urethra.

 

STEPS IN THE MICTURITION PROCESS

 

1. Voluntary relaxation of the external sphincter

2. Reduced sympathetic nervous system outflow

3. Smooth muscle relaxation with resultant funneling of the bladder neck and opening of urethra

4. Bladder contraction with evacuation of the bladder’s contents

 

URODYNAMIC EVALUATION OF THE FEMALE PATIENT

 

1. History, focusing on the following:

a. Existing systemic disorders

b. Congenital disorders

c. Psychosocial factors

d. Existing neurologic disorders

e. Disorders specific to the urologic tract

 

2. Physical examination

a. General examination

b. Evaluation of estrogen status

c. Examination of the vagina and periurethral area for signs of fistula, abscess, and diverticula

d. Examination for cystocele, rectocele, and enterocele

e. Rectal examination to assess sphincter tone and the bulbocavernosus reflex

f. Neurologic examination

(1) Mental status assessment

(2) Assessment of cranial nerves II through XII

(3) Cerebellar testing for truncal ataxia, gait ataxia, finger—nose test, heel—shin test

(a) Clinically, cerebellar lesions produce spontaneous, high-amplitude detrusor reflex contractions

(b) Poor hand coordination makes clean intermittent catheter-ization impractical

(4) Deep tendon reflexes

(a) Supranuclear lesions: hyperreflexia

(b) Cauda equina lesions: diminished or absent reflex

(c) Peripheral neuropathy: diminished or absent reflex

(5) Sensory assessment

(a) Pain and temperature awareness

(b) Position, vibration, light, and crude touch

 

3. Frequency/volume voiding diary: an investigational record of fluid intake, output, and other voiding characteristics occurring in a 24-hour period that includes the following:

a. Daily intake and output

b. Frequency of micturition

c. Time interval between voidings

d. Volume voided

e. Urgency

f. Incontinence

g. Number of continence pads used per day

 

4. Urinalysis and culture

a. Treatment for existing infections

b. Hematuria workup

 

5. Radiographic evaluation

a. Plain film of abdomen: to rule out bony abnormalities of the vertebral column and pelvis

b. IVP to assess the following:

(1) Upper tract anatomy and anomalies

(2) Ureters: ureteral ectopy and duplication

(3) Bladder configuration and abnormalities of contour and position

(4) Postvoid residual

(5) Vesicovaginal fistula

c. Video cystourethrography combines voiding cystourethrography (VCUG), fluroscopy, and pressure recordings of the bladder and abdomen along with urinary flow rates

 

6. Urethroscopy

a. Under direct visualization, the urethra is examined using a 0-degree, 5-degree, or 30-degree lens.

b. Gas urethroscopy allows measurement of urethral opening pressure, which in a normal patient is between 70 and 90 cm of water.

c. Water urethroscopy does not allow for urethral opening pressures.

d. The interior of the urethra is examined for any obstructing lesions, discharge from periurethral glands, diverticuli, or an ectopic ureter. The normal urethra has a pink epithelium.

e. The bladder is entered, and the urethrovesical junction is examined during bladder filling. The urethrovesical junction is normally described as round and symmetric. The trigone, located on the floor of the bladder, is pale pink. The ureteral orifices appear as slitlike openings on the floor of the bladder and should be observed for expulsion of urine.

f. The following changes are seen with bladder filling:

(1) The urethrovesical junction closes.

(2) The periurethral striated muscles tighten (Table 1).

 

7. Residual urine

a. Integrates the activity of the bladder and outlet during the emptying phase of micturition3

b. Defined as the volume of fluid remaining in the bladder immediately following the completion of micturition

c. Estimated by using the following:

(1) Catheter

(2) Cystoscopy

(3) IVP

(4) VCUG

(5) Radioisotope studies

d. Findings

(1) Increased residual (>100 cc): failure to empty. Possible causes include the following:

(a) Anxiety (if suspected, repeat test)

(b) Increased outlet resistance

(c) Decreased bladder contractility

(d) Combination of all of the above

(2) No residual of significance (<100 cc). Possible causes include the following:

(a) Normal function

(b) Increased bladder contractility

(c) Incompetent sphincter

 

Table 1 Urethroscopy of Normal and Abnormal Patients
Dynamic Function
of the Urethrovesical Genuine Stress
Junction Normal Incontinence Unstable Bladder
Empty bladder Closed Closed Closed
Partially filled bladder Closed Slowly opens Closed if no vesical contraction
Full bladder Closed Slowly opens Closed if no vesical contraction
Holding Closes Sluggish closure Closes
Straining Remains closed Opens Remains closed if no vesical contraction
Coughing Remains closed Opens Remains closed if no vesical contraction
Vesical contraction Opens, then closes, Opens and remains open due to inability to suppress
with suppression
Ability to suppress Present Present Absent
a vesical contraction
Modified from Robertson JR: Dynamic urethroscopy. In Ostergard DR, Bent AE, editors: Urogynecology and urodynamics—theory and practice, Baltimore,
1991, Williams & Wilkins.

 

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