Urodynamic studies (UDS) are tests that evaluate bladder, urethral, and sphincter function; identify abnormal voiding patterns; and check status of neuroanatomic connectives between brain, spinal cord, and bladder. Types of UDS include the cystometrogram (CMG), anal sphincter EMG, urethral pressure profile (UPP), and voiding cystourethrogram (VCUG).

A CMG helps determine the size of the bladder and how it functions by measuring how much urine the bladder holds, how full it is when the urge to void occurs, and the pressure of urinary flow. A UPP is a test that records the resistance of the urethra to fluid flow. An anal sphincter EMG assesses pelvic floor tonicity. The combined measurement of the CMG and the anal sphincter EMG provides information about how the bladder adapts to being filled as well as how it reacts to the filling itself. A VCUG is imaging using fluoroscopy to evaluate urethra and bladder size by instilling contrast into the bladder via a catheter and obtaining x-rays while voiding. It can be used to assess reflux and stress incontinence in women and to identify posttraumatic urine extravasation.

UDS are indicated in an incontinent person and when there is evidence of neurologic disease (neurogenic bladder), spinal cord injury, dysuria, enuresis, infection, or specific neuropathies such as those found in multiple sclerosis, diabetes, and tabes dorsalis (degeneration of the sensory neurons to the brain).

Procedures

1. CMG:

   1. Have the patient void and record urine flow rate, voiding pressure, and amount of urine voided.

   2. Insert a nonlatex double-lumen catheter into the bladder. Place adhesive patch electrodes parallel on each side of the anus and attach a ground to the thigh. Measure the residual urine. Connect the catheter to the cystometer. (A cystometer evaluates the neuromuscular mechanism of the bladder by measuring bladder capacity and pressure.) The bladder is gradually filled with sterile saline or sterile water or carbon dioxide gas in predetermined increments, and pressure readings are taken at these increments. Water or saline offers a more physiologic result and is less irritating.

   3. Make observations during the CMG about the patient's perception of heat and cold, bladder fullness, urge to void, and ability to inhibit voiding when bladder contractions occur.

   4. Remove the catheter and patch electrodes when the bladder is completely emptied of fluid.

   5. Inject cholinergic or anticholinergic drugs to determine their effects on bladder function (after CMG procedure).

   6. Perform the cystometric study as a control, followed by repeat study 20-30 minutes after injection of the drugs.

   7. Be aware that a change in posture from supine to standing or walking may be required during the examination.

   8. Remember that sleep studies may be performed in conjunction with an EEG to evaluate persons having nocturnal incontinence.

   9. Pediatric CMG: The bladder is filled until the pressures reach 40-60 cm of water, the child voids around the catheter, or the child seems very uncomfortable. For older children, ask questions about bladder fullness, when they would normally void, and ask them to hold urine until extreme urgency ensues. Patients may void on the table with the catheter in place, or they may void in a special container that measures urine flow, voiding pressure, and length of time to void. These pressures are depicted on a graph.

2. UPP:

   1. Use a specially designed catheter, coupled to a transducer, to record pressures along the urethra as it is slowly withdrawn.

   2. Pediatric UPP: This profile assesses the functional urethral length as well as general competency of the urethra and sphincter. The same double-lumen catheter is used, which has premarked lines on it for both the CMG and the UPP. Slowly withdraw the catheter and note the pressures at the premarked spots.

3. Anal sphincter EMG:

   1. Apply electrodes next to the anus, and attach a ground to the thigh, or introduce a needle electrode into the periurethral striated muscle. These electrodes record electromyographic activity during voiding and produce a simultaneous recording of urine flow rate.

   2. Pediatric anal sphincter EMG: Patch electrodes record the coordination of the external sphincter and the pelvic floor muscle response to filling and the ability to inhibit bladder contractions. If the child voids on the table, the sphincter relaxes during voiding (which is normal).

4. VCUG:

   1. Instill an x-ray contrast medium into the bladder through a catheter until the bladder fills. Clamp the catheter and take x-rays with the patient assuming several different positions.

   2. Remove the catheter and take more x-rays as the patient voids and the contrast material passes through the urethra.

   3. Pediatric VCUG: Rarely are VCUGs done at the same time as EMGs. VCUGs are done in children to assess vesicourethral reflux, to identify structural abnormalities, and to evaluate for voiding dysfunction, and they are usually done as part of the workup before considering EMG.

5. See Chapter 1 guidelines for safe, effective, informed intratest care for all procedures.

Abnormal results reveal motor and sensory defects, altered pressures or bladder capacity, and inappropriate or absent contractions of the pelvic floor muscles and internal sphincter during voiding.

1. Bladder noncomplian During filling, the bladder is stiff, does not stretch as expected, and can possibly compromise kidney function over time. A large-capacity, low-pressure bladder (high compliance) may indicate chronic overdistention from infrequent voiding habits or disturbed muscle coordination.

2. Bladder instability (hyperreflexia): During filling, the bladder contracts involuntarily; this occurs when the pressures go up and down in a wavelike pattern during filling due to overactivity of involuntary contractions. The unstable bladder may have no symptoms; many times, no contractions are felt, but commonly, patients have frequency, urgency, and incontinence.

3. Vesicle-sphincter dyssynergia (disturbance of muscular coordination) is the most common cause of incontinence. This dyssynergia is thought to be responsible for incomplete emptying of the bladder, inappropriate voiding, perineal dampness, and predisposition to urinary tract infections.

4. Detrusor hyperreflexia: The patient cannot suppress voiding on command owing to upper or lower motor neuron lesions, as in cerebrovascular aneurysm, Parkinson disease, multiple sclerosis, cervical spondylosis, and spinal cord injury above the conus medullaris.

5. Detrusor areflexia occurs when the detrusor reflex cannot be evoked because the peripheral innervation of the detrusor muscle has been interrupted, resulting in difficulty in initiating voiding without a residual volume being present in the bladder. The cause may be associated with trauma, spinal arachnoiditis, spinal cord birth defects, diabetic neuropathy, or anticholinergic effects of phenothiazines. In postmenopausal women, the UPP may be altered because the mucosal sphincter is deprived of estrogen.

6. Urethrovesical hyperreflexia is caused by benign prostatic hypertrophy and stress urge incontinence.

Pretest Patient Care

1. Explain the purpose and procedure of the bladder function test, often done before and after certain types of spinal surgery. Be aware of the patient's potential anxiety or modesty concerns. Record signs and symptoms of incontinence and voiding problems.

2. Ensure that the patient is relaxed and cooperative for accurate results. For children, provide a favorite toy or book. Sedation is not given because patient participation is necessary to verify sensations and perceptions. However, the patient must avoid movement during the examination unless instructed otherwise.

3. Allow the test and filling of the bladder to continue until the patient either leaks or voids around the catheter.

4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Disorientation or inability of the patient to cooperate affects the test results.

Normal

• Normal bladder sensations of fullness, heat, and cold

• Adult: Normal bladder capacity of 400-500 mL; residual urine <30 mL; desire to void is at 175-250 mL; sensation of fullness felt at 350-450 mL; stream is strong and uninterrupted

• Normal voiding pressures and muscle coordination

• Normal rectal EMG readings; UPP readings normal

• Pediatric: Bladder capacity varies with age. Compliant bladder: Stretches to capacity without pressure increase. Bladder stability: No involuntary contractions