A Reliable Indicator of Urinary Dysfunction

By Helen Carcio, NP

Millions of men and women in the United States experience bladder dysfunction. Epidemiologic studies suggest that 15% to 30% of all adults in this country have some degree of incontinence.¹ The actual frequency is probably much higher considering the significant underreporting of the problem by patients reluctant to discuss such a private subject.

The pathophysiology of stress urinary incontinence, overactive bladder and interstitial cystitis remains unclear, and an evaluation of symptoms alone may be misleading because they are based on the patient's observations. Clinical evaluation of bladder dysfunction is necessary to correctly diagnose and treat these prevalent conditions. This is increasingly and appropriately becoming the responsibility of NPs in a variety of settings, including gerontology, gynecology, urology and primary care.

Urodynamic testing is emerging as a reliable indicator of overactive bladder and urinary incontinence and as a way to rule out the presence of interstitial cystitis. Additionally, it is useful in determining when surgical intervention is necessary and when neurological function is altered, and in assessing the nature of urinary retention.

Why Urodynamics?

Urodynamic testing is a valuable step in the evaluation and management of bladder dysfunction. It does not exist in isolation but as an integral part of a bladder health center or program. The establishment of a bladder health center is an exciting and challenging adventure for the entrepreneurial nurse practitioner. (Editor's note: For a full discussion of how to establish a continence care center, see Carcio H. Comprehensive continence care. The nurse practitioner's role. ADVANCE for Nurse Practitioners. 2003; 11[10]:26-36.)

There is a critical lack of services available to treat the growing number of men and women with bladder disorders. The considerations and components of a comprehensive bladder health program include diagnosis of the type of bladder dysfunction, behavior modification, assessment and treatment of vaginal atrophy, pelvic floor rehabilitation, pharmacologic therapy, and use of vaginal pessaries. Urodynamic evaluation is an important first step in the diagnosis of bladder dysfunction.

Urodynamic equipment is pricey (around $15,000), but the reimbursement level averages around $1,000 for a complete urodynamic assessment. The equipment is complex but user-friendly, and manufacturers provide ample training and follow-up.

Function of the Bladder

The bladder and urethra form a functioning unit that comprises the lower urinary tract system (LUTS). Simply put, their function is to store urine in the bladder and to empty the bladder through the urethra when appropriate. To accomplish this, coordination between the detrusor muscle of the bladder and the urethral sphincteric mechanism is necessary.

The bladder is a unique organ comprising a smooth muscle sphincter (involuntary) and a skeletal muscle sphincter (voluntary). During normal voiding, the detrusor muscle contracts, causing a rise in bladder pressure. Concomitantly, the sphincter relaxes and urine is released. In other words, the detrusor is passive when it is filling and active when it is emptying or undergoing unstable contraction. The urethra is active when it is filling — under constant innervation from the neurological system – and passive when it is emptying (Figure 1). Storage occurs when the pressure within the bladder is lower than the pressure within the urethral sphincter.

The urethra is all that stands between the bladder and outside world. Continence depends on several active and passive properties of the detrusor and urethra. The urethra is a highly distensible muscular tube. During bladder filling, it forms a watertight seal.

The most common bladder problems are the result of a failure to store or retain urine (incontinence), failure to empty (retention), or a combination of both. For a patient to remain dry, the pressure in the urethra must be greater than the pressure in the bladder during filling.

The Pelvic Floor

The bladder and urethra are supported by a flat group of muscles known as the pelvic floor. When the bladder is properly positioned in the abdominal cavity, both it and the bladder neck are above the pelvic floor muscles. These underlying muscles act as a backboard or trampoline to support the organs in the lower pelvis. There are no side wall supports. Some of these muscles form a u-shaped sling that attaches to the pubic bone in front and the coccyx in back, at the base of the spine. This creates a hammock-type structure to support the bladder in its proper place (Figure 2). As the sling stretches with conditions such as pregnancy, the support provided by the bladder decreases, and the base of the bladder and bladder neck fall below the pelvic floor, causing change in the relationship of the bladder and urethra to their surrounding structures. Bladder problems result.

Differential Diagnosis

To better understand why urodynamic testing is necessary, it is important to review the types of bladder problems and the factors that contribute to them. Incontinence is categorized as stress urinary incontinence (SUI), urge incontinence, overactive bladder, sensory urgency and overflow incontinence. Overflow incontinence will not be addressed here.

Stress Urinary Incontinence

Stress urinary incontinence is the involuntary leaking of urine during coughing, laughing, sneezing, heavy lifting, orgasm or strenuous activities. Although only small spurts of urine are typically lost, it is bothersome. Leaking occurs when the pressures pushing on the bladder from the abdomen are greater than the strength of the muscles of the urethra to hold urine in.

Stress incontinence can be diagnosed with a thorough history and physical examination. The exam may prompt leaking during various maneuvers. If the diagnosis is unclear, urodynamic testing is indicated to demonstrate incontinence during the filling cystometrogram. In a patient with SUI, leaking of urine can be demonstrated during a provocative maneuver such as a cough in the absence of detrusor contractions. Once the diagnosis of SUI is demonstrated, the cause can be further evaluated by performing the Valsalva leak point pressure study (VLLP) or the urethral pressure profile (UPP). These tests are detailed later in this article.

SUI is usually caused by reduced outflow resistance (inability of the urethra to remain closed under increased abdominal pressures). This is most often caused by hypermobility of the bladder neck. Less commonly, it is caused by intrinsic sphincter deficiency.

Hypermobility of the Bladder Neck

Hypermobility of the bladder neck occurs with pelvic floor muscle descent due to weakened pelvic floor muscles. It is the most common cause of SUI. This laxity can occur with aging, pregnancy or a precipitous delivery. It can also occur in young nulliparous women.

In the typical case, the backboard of the pelvic muscles absorbs the pressure from the abdomen and prevents this pressure from exceeding the pressure within the urethra. When the muscles are weak or lax, the bladder neck becomes displaced during activities that increase pressure within the abdomen (and ultimately, the bladder), forcing the urethra open.

Intrinsic Sphincteric Deficiency

Intrinsic sphincteric deficiency (ISD) occurs when the urethral sphincter does not close tightly and remains open at rest. A severe form of ISD is called a "stove-pipe" urethra that results in continuous leaking of urine with minimal exertion. ISD may be related to urethral scarring from previous incontinence surgeries, pelvic radiation, traumatic childbirth, radical prostatectomy or neurological conditions. Some experts believe all women with SUI have some degree of ISD.

Urge Incontinence

Urge incontinence is the involuntary leaking of urine usually accompanied by a strong urge to urinate. This is due to an uninhibited detrusor contraction (detrusor instability). It is of unknown etiology. Leaking is often associated with certain triggers, such as approaching a toilet, putting a key into a lock, washing dishes, or even pumping gas. The bladder contracts uncontrollably, often emptying all its contents. Urine loss can occur as drops or "gushes," depending on how much urine is in the bladder.

Overactive Bladder

Overactive bladder is characterized by a strong feeling of urgency that may be accompanied by frequency of urination and incontinence. It is caused by overactivity or uncontrollable contractions of the bladder muscle (detrusor muscle). The etiology is unknown. Two to four nighttime trips to the bathroom are common.

The detrusor instability of overactive bladder can be demonstrated during filling cystometry by noting involuntary phasic detrusor contractions that are synchronous with patient complaints of urgency. This urgency may or may not result in leakage.

Mixed Incontinence

Mixed incontinence is a combination of stress and urge incontinence that is more common as patients age. The incontinence is often described as urge dominant or stress dominant, depending on which symptoms are more prevalent.

Sensory Urgency

Sensory urgency occurs in men and women who void "just in case." This causes the detrusor muscle to become more sensitive to low volumes and may be a conditioned response.

Patient Evaluation

Patient assessment begins with a medical history and examination, which may reveal abnormalities within the lower abdomen or pelvis that are contributing to the lower urinary tract symptoms. Table 1 outlines the components of the evaluation.

Voiding Diary

A voiding or bladder diary must be completed and documented before urodynamic testing and is an essential component of the assessment process. Medicare requires this documentation. Voiding diaries are important diagnostic tools that describe the patient's day-to-day bladder habits and patterns related to urination. It is best to record on 3 consecutive days, with one being a weekend. Give the form to the patient during the initial visit and instruct him or her to return it at the next visit.

The voiding diary is a simple, noninvasive tool that helps define the severity of symptoms, adding objectivity to the history. Ask the patient to document the time and amount of fluid intake (to identify bladder irritants), the time of each void, each episode of accidental leakage, and the volume of urine lost. The patient should record this information in terms of large (>¼ cup), medium (<¼ cup) or small (dribbles). A measuring "hat" and bladder diary form are available from Pfizer. The diary can be downloaded at http://www.detrolla.com/diary.asp.

A voiding diary allows patients to focus on their behavior and how it relates to overactive bladder and incontinence symptoms. Sometimes the mere keeping of the diary is therapeutic, and the continence improves once a causal relationship is established. It is also helpful for the patient to repeat the voiding diary at certain points during the treatment program to document improvement.

The Setting

Minimal space is needed to perform urodynamic evaluation. The equipment is usually compactly attached to a pole mounted on wheels (Figure 3 shows one example, the EasyPro by SRS Medical). Urodynamic testing equipment can be transported in and out of the room or stored in a corner. Ideally, a bathroom or a commode with curtain should be nearby, to allow the patient to void in privacy.

Patient Preparation

Prepare the patient by explaining the various phases of the testing procedure and showing the equipment that will be used. To avoid an inaccurate result, it is critical for the patient to be relaxed during the testing. Each patient needs to know that he or she will be asked to respond to various subjective sensations as the bladder is being filled and to report any feelings of urgency or discomfort. Additionally, each patient will be asked to cough, push or even jump during the test.

Explain that the purpose of the test is to reproduce the symptoms experienced during routine activities of daily living. Also, explain that the patient is expected to "leak" and should not to be embarrassed by it. Many patients also are self-conscious about passing gas. Reassure them that both these events are normal and expected.

Urodynamic Assessment

Urodynamic testing provides objective information about motor and sensory function of the lower urinary tract system. It evaluates and documents bladder and urethral function and provides useful information about detrusor function.²

Typical patient complaints that lead to a urodynamic evaluation include the following:

• incontinence

• nocturia

• frequency

• urgency

• pelvic pain

• slow stream

• hesitancy

• postmicturition dribble.

Urodynamic testing offers specific tests that can be tailored to each patient based on his or her presenting history and physical examination. Table 2 lists indications for urodynamic testing.

Preparation

Urinalysis must be performed before urodynamic testing to rule out urinary tract infection (UTI). The presence of leukocytes and nitrites on a Multistix reagent strip is enough to indicate infection. If hematuria is identified, consider referring for cystoscopy. If an infection is present, urodynamic testing should be delayed until the patient is appropriately treated and the culture is negative. A UTI may falsely alter the test result, causing bladder contractions related to the infection. A loss of bladder compliance may also occur.

Postvoid Residual

The amount of postvoid residual is the integral result of bladder contractility and urethral resistance testing. A high residual may indicate an inability to contract against an increase in urethral pressure or a hypotonic bladder. Measurement is more accurately recorded with a catheter than ultrasound. A postvoid residual of 25% or less of voided volume is acceptable. If a patient voids 400 cc and the postvoid residual is 60 cc, would the residual be considered normal? Yes it would, because 25% of 400 cc is 100 cc, and the postvoid was less than that (60 cc).

The Testing Procedures

A list of possible tests available with routine urodynamic testing appears below. The test choice should be appropriate for the overall assessment of the clinical problem.

• uroflow (urine flow) study

• cystometrogram (CMG)

• urethral pressure profiles

• Valsalva leak point pressures

• pressure or flow studies

• electromyography (EMG)

• videourodynamics (discussion is beyond the scope of this article).

Uroflow

A complex uroflow is often the first study during urodynamic testing. It is a simple, noninvasive and useful screen. Uroflow measures volume voided, flow pattern, ability of the bladder to empty, and bladder capacity. It is dependent on bladder contractility, proper relaxation and patency of the urethra.³ The flow rate is measured with a flowmeter, a device that records the amount of fluid passed over a period of time. It is an excellent screen to differentiate abnormal detrusor function from outlet obstruction caused by an enlarged prostate or a prolapse.

This test is usually performed prior to CMG testing. The patient should arrive with a comfortably full bladder (between 150 cc and 200 cc). To avoid overfilling and discomfort, don't keep the patient waiting too long.

It is important to create a private, relaxing environment conducive to voiding the way patients usually do at home. Patients should use whatever position they normally use to void, whether standing or sitting or somewhere in between. A normal flow rate is a smooth, bell-shaped curve. Normal voiding time (the time it takes to completely empty the bladder) is usually 20 to 30 seconds (Figure 4).

Complex CMG

Complex CMG is the major diagnostic portion of the urodynamic assessment. It assesses bladder function by measuring bladder filling and storage and recording the pressure volume (pressure within the bladder compared with the amount of fluid in it) relationships of the bladder.⁴

The purpose of the cystometric examination is to reproduce the patient's urinary symptoms in the clinical setting to observe events that may or may not affect bladder function. CMG documents the presence of uninhibited detrusor contractions related to overactive bladder and further documents whether any leaking is related to urge incontinence or stress incontinence.

Cystometry measures the pressure-volume relationships in the bladder during filling and storage. Four major bladder functions are assessed: stability, sensation, capacity and compliance.

Stability

Stability is related to the presence or absence of detrusor contractions. The normal bladder is stable. It should not contract during filling or storage. Abnormal detrusor contractions may be related to bladder outlet obstruction, overactive bladder, local irritation, chronic UTIs, the presence of a cystocele, or neurologic diseases involving the brain or spinal cord.

Capacity

Capacity is the total amount of fluid the bladder can hold. The normal amount for an adult is 400 cc to 500 cc. Abnormal findings of a small-capacity bladder may be associated with detrusor instability, sensory urgency, incontinence, infection or low bladder compliance (unable to easily stretch to fill). Related signs and symptoms might include urinary frequency, urgency or urge incontinence. A large-capacity bladder may be related to diminished sensation, chronic overdistension, outflow obstruction, a noncontractile or underactive detrusor, or social inhibitions.

Sensation

Sensation is the subjective response to bladder filling as communicated by the patient. Describe how the patient should interpret the different sensations by giving examples describing the various parameters for each (first sensation at 90 cc to 150 cc, second sensation at 200 cc to 300 cc, and third sensation at 400 cc to 500 cc). You might describe the second sensation in the following manner: "Picture yourself driving along the interstate and you feel a need to go to the bathroom. Tell me when you would start looking for the nearest exit that might have a bathroom." And for the third sensation, "Let me know when all thoughts of finding the nearest bathroom are gone, and you are now looking for the nearest tree."

These scenarios can be presented with humor, facilitating relaxation. Filling sensations may be heightened by any anxiety or discomfort the patient may feel during testing. Distraction and relaxation may be one of your greatest challenges during the urodynamic procedure. Ask patients to report any sensations they feel as the bladder slowly fills.

Diminished sensations may be due to chronic obstruction or overdistension, which may be related to neuropathies. Hypersensation or urgency may be caused by detrusor instability, UTIs, interstitial cystitis, bladder calculi or tumors. Signs and symptoms may include urgency, frequency or bladder pain.

Compliance

Compliance is the stretching ability of the bladder to accommodate increasing volumes. The bladder normally distends and stretches with filling, accompanied by only a slight rise in bladder pressure as maximal capacity is reached. Much like the stretching of a balloon, compliance is the elastic property of the detrusor muscles to stretch to normal capacity while maintaining low pressures.

Low compliance may be related to conditions that affect the bladder wall, such as interstitial cystitis, bladder cancer and radiation cystitis. A hypercompliant bladder has a large capacity to store fluid at very low pressures. Eventually this may lead to urinary retention as sensation and contraction become affected.

The CMG Procedure

Before CMG, patients should be mobile and alert. They should not take any medications that could alter bladder function (e.g., anticholinergics). Relaxation is imperative. A tense patient often unconsciously braces against leaking. Reassure patients that every effort will be made to make them comfortable during the procedure.

Use low lighting and a pleasing room decor to make the equipment seem less imposing. The patient's rectum should be as empty as possible (an enema is usually not necessary), and any supportive devices (pessaries) should be temporarily removed. If a prolapse, cystocele or rectocele is present, repeat a portion of the CMG with the pessary in place.

Clean the urinary meatus and catheterize the patient. Document any postvoid residual. If the patient's history or bladder diary indicates a suspected large residual, use a larger red rubber catheter rather than the urodynamic catheter. The larger the lumen, the more readily the urine will drain. Note that you cannot bill for performing a postvoid residual when it is part of a urodynamic study.

This first catheter inserted into the bladder measures the vesical pressure, which is the pressure inside the bladder. It 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 the detrusor muscle is exerting on that fluid. The pressure in an empty bladder is usually called resting pressure, and it changes with position. Normal bladder resting pressures vary between 8 cm and 40 cm of water, depending on the particular patient and position during study

Liquid or gas may be used to fill the bladder. Liquid is preferred because it is more physiologic and less irritating to the bladder. The fluid should be room temperature. Fill the bladder using a slow, constant infusion rate while you record and monitor changes in pressures.

Place a second catheter (abdominal) in the vagina, except in cases of severe prolapse. This catheter records pressure in the abdominal or pelvic area. In men, place the catheter in the rectum. Rectal placement is considered more invasive in women, particularly those who are older, and may not be as accurate in the presence of stool or hyperperistalsis of the bowel. Secure both catheters to the thigh (Figure 5).

The use of a second catheter to measure intra-abdominal pressures should be a routine part of urodynamic study. Use of the second catheter constitutes a complex or multichannel CMG. Abdominal pressure information is significant to note, since the bladder is contained in the floor of the abdominal cavity. It is important to isolate the extrinsic pressures emanating from the abdomen from the intrinsic activities occurring in the bladder. A major purpose of the CMG is to document detrusor contractions by noting any rise in detrusor pressure within the bladder. The abdominal catheter documents the presence of abdominal artifacts such as gas, straining or weight of the abdominal contents, which are subtracted from the recorded bladder pressure to arrive at the "true" pressure within the bladder. For example, if a patient coughs, pressures transmitted to the bladder will rise due to the increased pressure from the abdomen caused by the cough. The detrusor pressure does not change. The urodynamic equipment automatically subtracts any abdominal pressure (Pabd) from those recorded within the bladder (Pves) to arrive at the "true" detrusor pressure (Pdet). Conversely, if a detrusor contraction increases the bladder pressure, only the bladder catheter is affected. The abdominal catheter remains stable.

These pressures are recorded and printed out as the Pves, Pabd and Pdet and are shortened versions of the function they perform (Table 3).

Testing may be performed with the patient standing, sitting or supine, depending on his or her mobility and the required testing parameters. Reproduce the symptoms noted during the patient's normal activities of daily living. Standing will more accurately reproduce leaking associated with stress incontinence.

Fill the bladder slowly, to replicate normal bladder filling. Once the infusion begins, monitor the screen for any changes in pressure, and correlate these changes with symptoms and subjective responses. Urodynamic equipment features markers to press in response to observed "events" demonstrated by the patient. Using a remote control, you can signal events as they occur (e.g., cough, sensation, desire to void, urgency, leaking).

Note and record any episodes of leaking as the bladder fills or the patient strains or coughs. With a good light source, directly observe the urinary meatus for any leaking. This is easy to view in men but more difficult in women. It is also embarrassing to women to have someone's eyes at the level of the vulva. An alternative method for women is to firmly press a drape sheet against the urinary meatus. Leaking is felt as wet, cool fluid escaping through the opening. The fluid is more accurately felt than seen within the folds of the vulva. An additional bonus is that the amount of leaking can be subjectively observed by the size of the circle of wetness absorbed on the drape. The equipment has an event marker labeled "leak" to press when leaking occurs.

Provocative Maneuvers

It is sometimes helpful to use provocative maneuvers to evoke a bladder contraction or an episode of leaking. Uninhibited detrusor contractions and urge incontinence may be stimulated by triggers during activities of daily living. Such triggers may be replicated in the clinic by turning on a trickle of running water or jingling car keys. Contractions or leaking may be stimulated in both detrusor instability and SUI by asking the patient to cough, change position or bounce on the heels.

Interpretation Results

Normal sensation and compliance in the absence of detrusor contraction or leaking is considered a normal study. The detrusor muscle will generate a zero or very low recording and will only increase significantly during voiding.

Any nonvolitional elevation of the Pdet, especially if associated with a strong urge, is a detrusor contraction indicating detrusor instability.⁵ In some cases, detrusor contractions do not occur despite a clear history of bladder overactivity. Continue to fill the bladder, using provocative measures such as coughing or heel bounce. Be mindful of the unnatural and uncomfortable situation the patient is in. A patient's inability to relax may contribute to a false-negative result because the pelvic floor remains tightly contracted, inhibiting any detrusor contractions.

Hypermobility vs. Sphincteric Deficiency

Identify the cause of stress incontinence that is usually associated with hypermobility of the bladder neck or, less commonly, intrinsic sphincteric deficiency. The result will determine the type of surgery required to control leaking. Hypermobility and ISD can be differentiated from each other by evaluating the leak point pressure (LLP) and the urethral pressure profile (UPP).

Valsalva Leak Point Pressure Study

The valsalva leak point pressure study (VLLP) measures and records the amount of abdominal pressure necessary to cause leaking in response to maneuvers such as straining or Valsalva. It assesses the competency of the urethral closure mechanism.

The study is best performed with the bladder comfortably full at 150 cc to 200 cc. This can be accomplished two ways: The infusion during the CMG study can be paused at the appropriate volume, or some fluid can be drained out of the bladder at the end of the test. The latter would be most appropriate if the uroflow is done at the end of the CMG study and would serve to drain the fluid to a more appropriate volume for the uroflow.

The purpose is to observe and document the time the patient leaks during the various phases of testing. Ask the patient to slowly but forcefully bear down as if straining to have a bowel movement. The leak event marker records the amount of pressure required to cause leaking at the precise moment the leaking occurs. Again, it is important to note this either by direct observation or blotting. If the patient does not leak, ask him or her to cough strongly, using repeated coughs to initiate leaking. If the patient still does not leak, restart the infusion and repeat the test at various intervals of bladder fullness.

The VLLP is measured by subtracting the resting bladder (vesical) pressure from the pressure that caused the leaking. Note whether the VLLP was recorded during a detrusor contraction. This test may be repeated again a few minutes after the first one.

A leak point pressure of 60 or less indicates the presence of ISD. For example, if a resting vesical pressure (pVes) was 25 cm H₂0 at baseline and the total bladder pressure during Valsalva was 65 cm H2O at leakage, the VLLP would be 65-25 = 40.

Urethral Pressure Profile

The urethral pressure profile (UPP) records and documents the competency of the urethral sphincter by measuring the pressures along the urethra and the resistance of the urethral walls.6 When performed in addition to the VLLP, this test helps differentiate between bladder neck hypermobility and ISD. It is usually performed at the end of the CMG when the bladder is full and before the pressure-flow study. The patient may feel somewhat uncomfortable because of the full bladder. Slowly pull the catheter through the bladder neck, urethra and sphincter. Pressure will rise as the catheter is pulled out of the bladder and into the urethra. The peak pressure is usually the external sphincter. The pressure will again fall as the catheter is further withdrawn. Try not to pull the catheter out completely, since the catheter should be withdrawn and reinserted two or three times to document a consistent pattern.

Results are automatically calculated by most types of urodynamic equipment. It can also be calculated by subtracting the resting bladder pressure (Pves) from the urethral closure pressure. Pura Ð Pves = Pcls. The maximum urethral closure pressure (MUCP) is determined by further subtracting the Pves pressure from the maximum urethral pressure (MUP), MUP Ð Pves = MUCP. The MUP is the highest pressure recorded as the catheter is pulled through the urethra.

Pressure-Flow Study

The pressure-flow study is the simultaneous measurement of bladder pressure (Pves) and urine flow during voiding. It measures the interaction between the bladder and sphincter. Most patients void by a combination of the forces within the bladder (detrusor contractions) and abdominal exertion. A pressure-flow study can diagnose voiding dysfunction such as obstruction, dyssynergia or a weak, noncontractile bladder.

A pressure-flow study is usually performed immediately after filling cystometry, since the patient's bladder is full. Ask the patient to void, with catheters in place, into a commode. This can be quite awkward, and privacy should be maintained if possible. Since many people who undergo urodynamic testing are older, it is important that they are mobile enough to sit and stand for this portion of the test.

The urethral catheter is narrow enough for voiding to occur around it, but in some instances the patient is unable to. Measurement of detrusor pressure at maximum flow is important to note. Obstruction of urine passage (high pressure, low flow) can be distinguished from a lack of tone in the detrusor muscle (low pressure, low flow). Results may be further validated by recording the EMG.

Electromyography

EMG is the study of electrical activity in the striated muscles of the sphincter to assess the activity of the pelvic floor during filling and emptying. It may be performed during urodynamic testing, particularly if sphincter dyssynergia is suspected in relation to a neurological problem. Place surface patch electrodes around the anus at the 10 o'clock and 2 o'clock positions, with the ground wire on the thigh. Typically, the sphincter relaxes during voiding to allow urine to flow out freely. In the presence of sphincter dyssynergia, the pelvic floor muscles contract simultaneously with detrusor contractions. Voiding becomes difficult as the patient tries to void against the contracted pelvic floor. This usually indicates a neurologic problem. Signs and symptoms of sphincter dyssyngeriga include urinary retention, hesitancy and frequent UTIs due to incomplete emptying. Neurological conditions must be evaluated.

Follow-Up

The results of urodynamic testing are immediately available following the test and can be printed out in table form. This allows you to quickly interpret the results and discuss the next step in management.

Patients may feel some burning with urination for the first few hours following the test. Reassure the patient that this is expected and normal since a catheter was inserted into the urethra. Slight bleeding can result from the trauma caused by the catheter against the delicate mucosa. Continued hematuria and burning after 12 to 24 hours, particularly if accompanied by frequency, fever or dysuria, requires follow-up.

Reimbursement

The various components of urodynamic evaluation are reimbursed by most insurance plans. Proper documentation of urinary dysfunction is required by most insurance companies, including Medicare. When more than one procedure is performed during a single session (usually the case), Medicare reimburses the primary procedure, cystometry, at 100%. The subsequent procedures are then reimbursed at 50%. A 51 modifier is required. All studies are 5-series codes and considered procedures by payers. Table 4 lists typical Medicare reimbursement levels and codes. Reimbursement varies within state districts but usually by no more than 10%.

Simple CMG

Another procedure is important to learn but is not performed as part of urodynamic testing: the "simple" CMG or "eyeball" CMG. Although the complex CMG has edged it out in popularity, there is still a place for simple CMG in the evaluation of the patient with bladder dysfunction. It is a simple screen that can be done prior to the diagnostic CMG as part of the initial work-up.

Simple CMG is appropriate for patients who are not mobile enough to undergo complex CMG or for uncomplicated cases of stress or urge incontinence. Simple CMG can be performed in only 15 minutes, costs only a few dollars for equipment, and can be done by a single examiner. Medicare reimburses it at a rate of about $250. A nurse practitioner in a primary care setting who does not have access to complex CMG testing could use this valuable tool in the diagnosis of bladder problems.

Supplies required for a simple CMG are a 12- or 14-French red rubber catheter, Betadine swabs, a 50-cc to 60-cc catheter-tipped syringe without piston, a liter bottle of sterile water (room temperature), and absorbent pads.

Catheterize the patient, and record the postvoid residual. You can send the urine for culture or urinalysis at this time. Attach the syringe without the piston to the catheter, and use it as a funnel to fill the bladder. Hold the syringe 10 inches to 12 inches above the pubic bone, and slowly fill the bladder with warm, sterile water, 50 cc at a time (Figure 6). Pinch off the tube between each aliquot to prevent too much air from filling the bladder. As with the complex CMG, ask the patient to respond to sensations during filling and to report any urgency or discomfort. A major goal of the test is to note the presence or absence of involuntary bladder contractions, detected by continuous upward movements of the column of fluid. It can actually be quite dramatic. The contractions may be accompanied by leaking around the catheter or, if the contractions are strong enough, actual expulsion of the catheter. Observe for the presence of any abdominal straining, which would alter the test results. Contractions or severe urgency at relatively low bladder volumes (250 cc) suggest urge incontinence. Ask the patient to cough or strain, and document any leaking. Record the maximum bladder capacity at the end of the test.

Although simple CMG can provide useful information, more subtle abnormalities may go unobserved, or the results may be inconclusive. Consider a complex CMG next, particularly if the patient does not respond to the initial treatment plan.

A Valuable Tool

Urodynamic testing is an essential skill for the NP who is interested in caring for the generation of baby boomers and their associated bladder problems. It can be an exciting part of a nurse practitioner-managed comprehensive bladder health program and center.

References

1. Wagneer TH, Hu TW. Economic costs of urinary incontinence. (Editorial). Int Urogynecol/Pelvic Floor Dysfunction. 1998;8:127-128.

2. Chapple C, MacDiarmid SA. Urodynamics Made Easy. 2^nd ed. Edinburgh, Scotland: Churchill Livingstone; 2000: 457-463.

3. Berger Y. Outcomes and obstacles of urodynamics. Contemporary Urology. 1995;8:15-31.

4. Schaefer W. Principles and clinical application of advanced urodynamic analysis of voiding function. Urol Clin North Am. 1990;17:553-566.

5. Griffiths DL. Assessment of detrusor strength or contractility. Neurourol Urodynamics. 1991;10:1-18.

6. McGuire EJ, Fitzpatrick CC. Clinical assessment of urethral sphincter function. J Urol. 1993;150:1452-1458.

Helen Carcio is a women's health nurse practitioner at Pioneer Women's Health in Greenfield, Mass., where she specializes in the treatment of incontinence, infertility, vulvovaginitis and menopause. The National Association for Continence awarded her its Continence Care Champion Award in 2004. She created and operates two continence treatment centers, one at Pioneer Women's Health and another at Grace Urological in Brattleboro, Vt. Carcio, who is a member of the ADVANCE for Nurse Practitioners editorial advisory board, is also an adjunct graduate nursing professor at the University of Massachusetts and is nearing completion of her PhD.