eMedicine World Medical Library

Artificial Urinary Sphincter

Last Updated: September 17, 2004
Synonyms and related keywords: AUS, AMS 800, incontinence, stress incontinence, urge incontinence, overactive bladder, post-prostatectomy incontinence, stress urinary incontinence, urinary sphincter, type III stress urinary incontinence, intrinsic sphincter deficiency, ISD, incompetent urethra

  AUTHOR INFORMATION  

Author: Jong M Choe, MD, FACS, Director of Continence and Urodynamic Center, Assistant Professor, Department of Surgery; Division of Urology, University of Cincinnati

Jong M Choe, MD, FACS, is a member of the following medical societies: American Association of University Professors, American College of Surgeons, American Medical Association, American Urological Association, International Continence Society, Ohio Urological Society, and Society of University Surgeons

Editor(s): Edward David Kim, MD, Associate Professor, Department of Urology, University of Tennessee School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, Pharmacy, eMedicine; Shlomo Raz, MD, Professor, Department of Surgery, Division of Urology, University of California at Los Angeles School of Medicine; J Stuart Wolf, Jr, MD, Director of Michigan Center for Minimally Invasive Urology, Associate Professor, Department of Urology, University of Michigan Medical Center; and Stephen W Leslie, MD, FACS, Founder and Medical Director, Lorain Kidney Stone Research Center, Clinical Assistant Professor, Department of Urology, Medical College of Ohio
  INTRODUCTION  

A biological urinary sphincter prevents urinary flow by mucosal coaptation, compression, and pressure transmission. An artificial urinary sphincter (ie, AMS 800) mimics the biological urinary sphincter by providing a competent bladder outlet during urinary storage and an open unobstructed outlet to permit voluntary voiding.

An artificial urinary sphincter is the only device that most closely simulates the function of a biological urinary sphincter. Recent advances in mechanical design, applications of new technology, and lessons learned from clinical experience have inspired notable improvements.

Novel and ingenious in technical design, the AMS 800 device has restored the quality of life in thousands of patients plagued by stress urinary incontinence. The AMS 800 prosthesis is the only reliable surgical treatment that provides lasting cure rates for men who are incontinent postprostatectomy.

History of the Procedure: Scott et al introduced the first artificial urinary sphincter in 1973. Called the AS 721, it consisted of a fluid reservoir, inflation pump, deflation pump, and an inflatable cuff with 4 unidirectional valves. The fluid within the sphincter components conveyed the hydraulic pressure to the cuff. Unfortunately, it was mechanically unreliable and had high urethral erosion rates.

In 1974, a newer model (ie, AS 761) emerged. This model offered a pressure-regulating balloon that allowed automatic cuff closure. This pressure-regulating balloon provided a constant, predetermined pressure within the hydraulic system so that pressure-volume relationship became very predictable.

The AS 761 device was quickly modified into the AS 742 model. This newer sphincter eliminated the need for an inflation pump. The pressure-regulating balloon functioned as a reservoir for cuff fluid. A delay-fill resistor allowed enough time for the patient to void to completion before the urethral cuff closed. However, this prosthesis still was not ideal for patient use.

Introduced in 1979, the AS 791/792 device featured a control assembly that merged the valves and the resistor into a single unit. Surgical implantation was easier with fewer components and less connections. However, the control pump did not have “on-off” capability. The risk of urethral atrophy and cuff erosion remained high. A second operation was required for activation of this device.

Through continued evolution and improvement, the AMS 800 device was introduced in 1983. During the modification process, the control assembly (ie, valves and resistor) was moved into the pump chamber. This model featured a new locking mechanism that allowed the cuff to remain either in open or in closed position; thus, the cuff could be left in a deflated (open) state after implantation and could be activated 6-8 weeks later without the need for a second operation.

Problem: An artificial urinary sphincter is reserved for treatment of complex stress urinary incontinence—type III stress urinary incontinence or intrinsic sphincter deficiency (ISD). Intrinsic sphincteric dysfunction is the inability of the urethra to maintain effective resting urethral closure pressure to keep the patient clinically dry at rest and during periods of physical activity.

Etiology: Cases of intrinsic sphincteric dysfunction involve men with a history of radical prostatectomy or transurethral resection of the prostate (TURP); patients with myelomeningocele, previous pelvic trauma, or history of pelvic radiation; and women with failed anti-incontinence procedures.

Pathophysiology: The normal voiding cycle requires that the urinary bladder and the sphincter work as a coordinated unit. The urinary bladder has 2 functions: it relaxes to store urine and contracts to eliminate urine. During urinary storage, the bladder is placid and acts as a low-pressure reservoir. During voiding, the bladder actively contracts to act as a pump. The urinary sphincter has 2 functions: it contracts to store urine and it relaxes to eliminate urine. During urinary storage, the urinary sphincter remains closed to prevent urine loss. During urination, the urinary sphincter opens to allow unobstructed urinary flow.

Urinary incontinence results from a dysfunction of the bladder, the sphincter, or a combination of both. Bladder overactivity causes urinary frequency, urgency, and urge incontinence. Bladder underactivity causes urinary retention. Sphincteric overactivity causes urinary retention. Sphincteric underactivity results in stress incontinence. A combination of bladder overactivity and sphincter underactivity results in mixed incontinence—stress and urge.

Intrinsic sphincteric dysfunction, or type III stress incontinence, is a complex form of stress incontinence whereby the urethra remains open at all times. Risk factors for ISD include radical prostatectomy, TURP, previous bladder neck surgeries, pelvic radiation, and neurologic disorders.

A common denominator of intrinsic sphincteric dysfunction is low urethral resistance at rest and during periods of physical activity. Whenever the intravesical pressure becomes greater than the urethral resistance, stress incontinence ensues. A reliable method of restoring continence is by artificially increasing the urethral resistance using an implantable device such as an artificial urinary sphincter (ie, AMS 800). The main criterion for implanting an artificial urinary sphincter is a normal detrusor in a setting of intrinsic sphincteric dysfunction.

Clinical: Patients with ISD present with classic history for stress urinary incontinence. They experience predictable loss of urine whenever the intravesical pressure exceeds that of the urethral pressure (eg, coughing, laughing, sneezing).

Often, these patients complain of involuntary urine loss when changing their body position (eg, rising from sitting position). Women with ISD experience more urine loss and require thicker pads compared to women with urethral hypermobility.

For patients with pure ISD, symptoms of urinary frequency, urgency, and nocturia typically are absent. However, when irritative voiding symptoms also are present, coexisting overactive bladder should be suspected.
  INDICATIONS  

Candidates eligible for artificial sphincter are those patients with type III stress urinary incontinence. Essential characteristics of an ideal patient include highly motivated personality, good manual dexterity, normal detrusor, absence of urinary tract infection (UTI), and realistic expectations.

  RELEVANT ANATOMY AND CONTRAINDICATIONS  

Relevant Anatomy: The urethra is composed of an inner epithelial lining, a spongy submucosa with rich vascular plexus, a middle smooth muscle layer, and an outer layer of fibroelastic connective tissue. The spongy submucosa is responsible for providing urethral occlusive pressure to create the “washer effect.” The ability of the urethral mucosa to coapt to generate an adequate urethral closing pressure is an important continence mechanism. Urethral smooth muscle and fibroelastic connective tissues serve to circumferentially augment the occlusive pressure generated by the submucosa.

The urinary sphincter is composed of an internal sphincter and an external sphincter. In females, the internal sphincter is composed of bladder neck and proximal urethra. In males, the internal sphincter is composed of bladder neck and prostate. Both males and females possess an external sphincter known as the rhabdosphincter. The rhabdosphincter is omega shaped and is composed of 2 types of striated muscle fibers, fast twitch and slow twitch. Contraction of fast twitch fibers causes sudden stopping of the urinary stream. This is known as the voluntary guarding reflex. These fibers are responsible for allowing Kegel exercises. Slow twitch fibers maintain the constant tonus of the external sphincter, which is important in daily physical activities. This is known as the involuntary guarding reflex.

Contraindications: Contraindications for artificial urinary sphincter include UTI, detrusor hyperreflexia, small capacity bladder, and poorly compliant detrusor. Preexisting UTI should be eradicated prior to sphincter implantation. Hyperreflexic detrusor generates high intravesical pressures that are transmitted to the upper tracts and cause renal damage. Small bladders and decreased bladder compliance should be managed by augmentation cystoplasty first. An artificial urinary sphincter may be placed at the same time as enterocystoplasty, or placement can be performed as a staged procedure. Occasionally a patient may have expectations of being completely dry and may not wish to deal with unforeseeable mechanical or surgical complications. These patients have unrealistic expectations for the operation as well as the device. Artificial urinary sphincters should not be placed in patients with unrealistic expectations.


  WORKUP  

Lab Studies:

  • Urinalysis and urine culture: The possibility of UTI should be ruled out before implanting an artificial urinary sphincter. The presence of a UTI is a contraindication to sphincter placement.
  • Serum white blood cell count (WBC): Systemic leukocytosis should be evaluated and treated prior to surgery.
  • Serum creatinine: The patient should have normal renal function prior to AMS 800 placement.

Imaging Studies:

  • Voiding cystourethrogram
    • This test is optional. This test can be used to assess bladder neck and urethral function (ie, internal, external sphincter) during the filling and voiding phases.
    • Voiding cystourethrogram (VCUG) allows radiographic observation of an incompetent bladder neck and coincident leakage during Valsalva maneuvers. VCUG is performed most often at the time of videourodynamics.

Other Tests:

  • Voiding diary: A voiding diary is a daily record of a patient's bladder activity. The diary is an objective documentation of a patient's voiding pattern, incontinent episodes, and any inciting events associated with urinary incontinence. Although not critical, a properly logged voiding diary may help influence diagnosis and therapy.
  • Standing cough stress test: The patient stands upright with feet shoulder width apart. Place a large towel under the patient's feet or a small trash can between the patient's feet to catch the flow of urine. Instruct the patient to perform the Valsalva maneuver and cough in gradients (ie, mild, moderate, severe). Observable urine leakage in this position constitutes a positive test result. If the bladder is empty at the time of the Valsalva maneuver or cough, it will be a falsely negative test result.
  • Urodynamic studies
    • Urodynamics is a means of evaluating the bladder capacity, compliance, abdominal leak point pressure, the presence of phasic contractions, and the pressure-flow relationship between the bladder and the urethra.
    • Simple urodynamics involves performing a noninvasive uroflow, obtaining a postvoid residual (PVR) urine volume and a single channel cystometrogram (CMG). A single channel CMG (simple CMG) is used to assess the first sensation of filling, fullness, and urge. Bladder compliance and the presence of uninhibited detrusor contractions (eg, phasic contractions) can be noted during this filling CMG. A simple CMG may be performed using water or gas (ie, carbon dioxide). Water is the most common filling medium.
    • Multichannel urodynamic studies are more complex than simple urodynamics and can be used to obtain additional information, including a noninvasive uroflow, PVR, filling CMG, abdominal leak point pressure (ALPP), voiding CMG (pressure-flow), and electromyogram (EMG). Water is the fluid medium used for multichannel urodynamics.
    • The most sophisticated study is videourodynamics, which is the leading standard in the evaluation of a patient with incontinence. In this study, the following are obtained: noninvasive uroflow, PVR, filling CMG, ALPP, voiding CMG (pressure-flow), EMG, static cystogram, and VCUG. The fluid medium used for videourodynamics is radiographic contrast.
    • Performing urodynamics

      • Instruct the patient to arrive at the urodynamic laboratory with a relatively full bladder. Note that patients with ISD have low volume or empty bladder due to continuous incontinence. Perform a noninvasive uroflow and PVR.

      • Perform flexible cystoscopy. Survey the entire bladder urothelium and then retroflex the cystoscope to examine the bladder neck. Drain the bladder. Place a urodynamic urethral catheter, rectal tube, and EMG electrodes.

      • Rotate the patient to a standing position and equalize transducers. Commence bladder filling using room temperature water or contrast (Conray). Cold water may evoke false-positive detrusor contractions (phasic contractions). Fill the bladder at medium rate (eg, 60 mL/min). Assess the first sensation of filling, fullness, and urge. Note bladder compliance and mark the presence of uninhibited detrusor contractions.

      • When the bladder fills to 250 mL, measure the ALPP. Instruct the patient to perform the Valsalva in gradients (ie, mild, moderate, severe) followed by cough (ie, mild, moderate, severe). Observe the urine leakage fluoroscopically and by direct inspection.

      • Following the ALPP measurements, finish the filling CMG to completion. When the patient has a strong desire to void, perform a voiding CMG (pressure-flow). At this point, note urodynamic parameters, such as maximal flow rate (Qmax) and detrusor pressure at maximal flow rate (PdetQmax).

      • During the voiding CMG, note the activity of the EMG electrodes and VCUG for possible detrusor sphincter dyssynergia (DSD). The presence of DSD is confirmed by increases in EMG activity during detrusor contraction or closure of the external sphincter on VCUG during voiding.

      • After the patient voids to completion, the videourodynamic study is complete. The patient is informed about the findings on urodynamic studies and is sent home on an oral antibiotic.
  • Pad test: Patients with classic ISD present to the office with a diaper or a pad in place. An adult male with a damp or wet pad inside his underwear has urinary incontinence unless proven otherwise.
  • Uroflow rate: The uroflow rate is a useful screening test used mainly to evaluate bladder outlet obstruction. The uroflow rate is the volume of urine voided per unit of time. Maximal flow rate (Qmax) greater than 15 mL/s may be considered within the reference range. Low uroflow rates (<15 mL/s) may reflect urethral obstruction, a weak detrusor, or a combination of both. This test alone cannot be used to distinguish between obstruction and an acontractile detrusor. Patients with ISD demonstrate uroflow rates within the reference range. A maximum flow rate (Qmax) of less than 15 cc/s with 150 mL of minimal void volume has been used to identify patients with significant bladder outlet obstruction in drug study trials (Ghormley, 1992; Lepor, 1990).
  • Electromyography: Electromyography (EMG) helps to ascertain the presence of coordinated or uncoordinated voiding. Failure of urethral relaxation during a bladder contraction results in uncoordinated voiding (ie, DSD). EMG is not necessary for evaluation of men who are incontinent postprostatectomy; however, EMG is used in combination during multichannel urodynamic studies.

Diagnostic Procedures:

  • Postvoid residual urine volume: This measurement is a part of the basic evaluation for urinary incontinence. Healthy men usually have a PVR volume of less than 100 mL. If the PVR volume is high, the bladder may be acontractile or the bladder outlet may be obstructed. Both of these conditions cause urinary retention from overflow incontinence. Patients with ISD have minimal postvoid residual urine.
  • Filling cystometrogram
    • A filling cystometrogram (CMG) assesses the bladder capacity, compliance, and the presence of phasic contractions. Most commonly, liquid filling medium is used. An average adult bladder holds approximately 450-500 mL of urine. During the test, provocative maneuvers, such as coughing, handwashing, sitting on the commode for 1 full minute, and heel jouncing, may help to unveil bladder instability.
    • A filling cystometry may be performed in the following ways:

      • Insert a catheter (connected to a special computer) into the bladder for a single channel cystometry. Information recorded by the computer is interpreted.

      • Eyeball cystometry does not require special computers. Perform bedside cystometry by inserting a catheter into the bladder and hanging the irrigant bag at a predetermined height (eg, 100 cm H2O) and observing the fluctuation of the meniscus within the water chamber during uninhibited detrusor contractions.

      • Eyeball cystometry using a flexible cystoscope is the same as eyeball cystometry except that the flexible cystoscope acts as the connection tubing. This allows simultaneous cystoscopy.

      • Multichannel cystometry is a more sophisticated method of measuring filling CMG where intravesical pressure (Pves), intra-abdominal pressure (Pabd), detrusor pressure (Pdet), and maximal flow rate (Qmax) are recorded simultaneously.
  • Voiding cystometrogram (pressure-flow study)
    • A pressure-flow study simultaneously records the voiding detrusor pressure and the rate of urinary flow. This is the only test that can assess bladder contractility and the extent of a bladder outlet obstruction. Pressure-flow studies can be combined with a voiding CMG and videourodynamic study for complicated cases of incontinence.
    • Note that most adult men normally void with detrusor pressures (Pdet Qmax) of 40-80 cm H2O. However, pressures of 20-30 cm H2O or lower are considered to be within the reference range if uroflow (Qmax) is within the reference range or high (Blaivas, 1996).
  • Abdominal leak point pressure
    • Abdominal leak point pressure (ALPP) measurements allow clinicians to classify stress urinary incontinence into type I, type II, and type III, or type II and III in combination. ALPP of 0-60 cm H2O is classified as type III stress urinary incontinence (ie, ISD). ALPP of 60-90 cm H2O is classified as type II/III stress urinary incontinence (ie, combination of urethral hypermobility and ISD). ALPP of 90-120 cm H2O is classified as type II stress urinary incontinence (ie, urethral hypermobility). ALPP greater than 120 cm H2O is classified as type I stress urinary incontinence.
    • ALPP should be measured when the bladder is half full (eg, 250 mL), and both the Valsalva and coughing maneuvers should be performed. Initially, instruct the patient to bear down in gradients (ie, mild, moderate, severe), and then note the ALPP as the lowest intravesical pressure (Pves) at which leakage is observed.
    • If Valsalva maneuvers fail to produce the desired response, instruct the patient to cough in gradients (ie, mild, moderate, severe) to obtain the ALPP. The lowest intravesical pressure (Pves) at which leakage is observed is the ALPP. The ALPP obtained with Valsalva maneuver is more accurate than the cough-induced ALPP. However, both techniques should be employed if Valsalva maneuvers fail to manifest stress urinary incontinence.
    • Alternatively, both Valsalva and cough-induced ALPP may be repeated by increasing the bladder volume in 100-mL gradients. Increasing the bladder volume reportedly increases the sensitivity of detecting ALPP.
    • Obtaining ALPP in male stress incontinence (ISD) is optional because men with type III stress incontinence, by definition, have ALPP less than 60 cm H2O.
  • Cystoscopy
    • The precise role of cystoscopy in the evaluation of female urinary incontinence is controversial because less than 2% of bladder tumors have been identified by routine cystoscopy. However, cystoscopy allows discovery of bladder lesions (eg, stitch in the bladder, bladder cancer, bladder stone) that would remain undiagnosed by urodynamics alone.
    • In male urinary incontinence, cystoscopy should be performed more routinely because a visual inspection of the urethra helps to establish the presence of urethral stricture, vesical neck contracture, or gross evidence of poor urethral coaptation and closure.
    • In general, cystoscopy also is indicated for patients reporting persistent irritative voiding symptoms or hematuria. Obvious causes of bladder overactivity, including cystitis, stone, and tumor, can be diagnosed easily. This information is important in determining the etiology of the incontinence and may influence treatment decisions.
  • Videourodynamics
    • Videourodynamics combines the radiographic findings of VCUG and multichannel urodynamics. Videourodynamics is the most sophisticated diagnostic test for a patient with incontinence. Videourodynamics may be used for evaluating any patient with lower urinary tract voiding dysfunction.
    • In the absence of videourodynamics, the clinician may obtain adequate information regarding male incontinence from (1) noninvasive uroflow and PVR and (2) simple cystometry in combination with cystoscopy.
  TREATMENT  

Medical therapy: No known reliable medical therapy for postprostatectomy male stress incontinence exists. Alpha agonists have not been demonstrated to be helpful in correcting male ISD. Periurethral collagen injections have been effective in improving stress incontinence symptoms, but they rarely provide lasting cure.

For women with intrinsic sphincter dysfunction, estrogen therapy and/or alpha agonists have been used with some improvement in symptoms. Periurethral collagen injections are most effective for women with ISD, producing cure rates that last as long as 1 or 2 years. Although the efficacy of periurethral injection therapy is better in women compared to men, it does not produce lasting cure.

Surgical therapy:

AMS 800 - The device

The most commonly used device today, the AMS 800 artificial urinary sphincter is composed of a pressure-regulating balloon, an inflatable cuff, and a control pump. The balloon has a dual function: it is a pressure regulator as well as a fluid reservoir. Balloon reservoirs come in 5 preset pressures (ie, 41-50, 51-60, 61-70, 71-80, and 81-90 cm H2O). The lowest pressure required to close the urethra is used. Balloon reservoirs typically are placed in the lower abdomen. For uncomplicated bulbous urethral cuffs, the most commonly chosen reservoir is the 61– to 70–cm H2O pressure balloon. For bladder neck cuffs, the 71– to 80–cm H2O balloon reservoir is chosen.

The inflatable cuff has a variable length that compresses the urethra or the bladder neck circumferentially. Cuff sizes range from 4.5-11 cm, in 0.5-cm increments. The cuff is placed around the bulbar urethra in adult males. For women and children, the bladder neck is chosen. The cuff size is based on the circumference of the bladder neck or the bulbar urethra. A properly sized cuff for the bulbar urethra ranges 4.5-5.5 cm in length. Most commonly, a 4.5-cm cuff is chosen for adult males. For the bladder neck, a 6.0- to 8.0-cm cuff is selected in women.

The control pump contains unidirectional valves, a delayed-fill resistor, a locking mechanism, and a deflate pump. The control pump is small and easily concealed within a subcutaneous pouch in the scrotum or the labia. The delayed-fill resistor is responsible for automatic cuff repressurization. The cuff inflation takes 3-5 minutes, although bladder emptying takes less time. A unique feature of this model is the locking mechanism that can keep the cuff deflated for a prolonged period. The locking mechanism is a small button located on the side of the control pump.

Mechanics of the AMS 800

The artificial urinary sphincter works on the basis of hydraulic mechanics. The isotonic fluid within the sphincter is transferred from the reservoir to the cuff and vice versa in a unidirectional fashion. When the sphincter is first activated (unlocked), the fluid from the reservoir travels down the pressure gradient to the cuff. The cuff gradually inflates to effectively close the urethra. This stores urine in the bladder and prevents urine loss. The device works in semiautomatic fashion, the cuff remaining closed at all times except when the patient opens the cuff for voiding.

To void, the patient must open the artificial sphincter. The patient manually squeezes the control pump that is located in the scrotum or the labia. When the control pump is squeezed, the fluid in the control pump is sent up to the balloon reservoir. It then automatically reexpands. As the control pump reexpands, it pulls the fluid out from the cuff. This causes the sphincter cuff to deflate. The patient repeats this maneuver (3-4 times) until the pump remains flat. This indicates that the cuff is completely empty.

At this point, the urine flows freely from the bladder. Urination commences until the bladder is empty. After 3-5 minutes, the fluid from the balloon reservoir automatically flows through a delay-fill resistor within the pump and down back to the cuff. When the cuff reinflates, the urethra becomes effectively closed and the patient becomes dry. The locking mechanism (button on the side of the control pump) allows the physician to lock the cuff in an open or closed position. Typically, the AMS 800 device is left locked (deactivated) in an open position at the time of surgical implantation. After adequate healing has taken place, the sphincter is unlocked (activated) by the physician. If the patient inadvertently locks the button when the cuff is closed, urinary retention occurs. Conversely, if the button is locked when the cuff is open, persistent incontinence occurs.

Limitations of the AMS 800

The AMS 800 device is an extremely reliable prosthesis that is easy to place. The patient satisfaction rate is high after successful implantation. Despite recent advances in mechanical design, certain limitations exist with this device. Mechanical malfunctions (ie, cuff leak, defective pump) and surgical problems (ie, pump migration, improper cuff size) require reoperation and sphincter revision. Urinary incontinence may arise from improper usage, fluid leakage, pressure atrophy, or cuff erosion. Urinary retention may occur as a result of particle obstruction or a tube kink in the system.

  • Silicone composition: The AMS 800 is composed of permeable silicone elastomer. Although relatively inert and resistant to body fluids, silicone deteriorates and loses tensile strength over time. Because it is permeable, fluid escapes over time, with resultant decrease in closing cuff pressure. The constant rubbing together of the 2 silicone components can lead to thinning of the silicone elastomer and exacerbate fluid leakage.

  • The hydraulic system: The balloon, cuff, pump, and connecting tubings are filled with iso-osmotic solution. Either isotonic sodium chloride solution or radiocontrast is used. The tonicity of the contrast is approximately 290-310 mOsm/L, similar to human intracellular and extracellular fluid. The use of hypo-osmolar or hyperosmolar fluid causes sphincter malfunction due to osmotic fluid shifts.

  • Pressure-regulating balloon: The fluid volume of the pressure-regulating balloon regulates the cuff pressure. A typical balloon reservoir holds 20-22 mL of iso-osmotic fluid. The pressure-volume relationship of the AMS 800 device is very narrow and sigmoid curve shaped. Small volume changes (ie, 2 mL) decrease its pressure characteristics; when the volume decreases below 14 mL, the pressure decrease is precipitous. A common cause of postactivation incontinence is fluid loss from the pressure-regulating balloon. The patient notices that the number of squeezes to deactivate the pump has decreased or the pump does not refill and remains flat. The incidence of balloon leak responsible for sphincter malfunction has been reported to be as high as 13% in some series.

  • Inflatable cuff: A common problem leading to delayed or persistent incontinence is fluid loss due to a wear defect in the cuff. The most common site of fluid leak is the lower surface of the cuff. In 1983, the inner surface of the cuff was reinforced with a layer of fluorosilicone gel to prevent friction between 2 leaflets. With this modification, the cuff leak rate decreased from 56% to 1.3%.

  • Connecting tubing: A short tube length may disrupt connecting junctions, causing a fluid leak or pulling up the control pump into the inguinal area, making device manipulation difficult. Excess tube length may lead to kinks, obstructing the system and causing urinary retention. Kinks are rare after 3 months of device implantation. In the past, tube kinks were the most common mechanical cause for surgical revision. With the advent of reinforced kink-proof tubing, no mechanical failures have been reported. However, tube kinks still may occur from tailoring connecting tubes to an improper length during the implant procedure.

  • Control pump: The control pump is cosmetically appealing due to its small size. Yet, its small size can be a handicap because some patients may have difficulty manipulating the pump. Labial or scrotal hematomas may displace the pump into an unfamiliar location. The pump may rotate upon itself and become kinked. Migration of the pump into the inguinal region may cause failure to deflate the cuff.

  • Locking mechanism: A major technologic advancement of the AS 800 is its locking mechanism. The disadvantage is that activating and deactivating the cuff using the locking mechanism is not always easy. Before locking the cuff, one must be sure that some fluid remains in the pump chamber. If the pump chamber is totally flat and empty, unlocking (activating) the cuff in the standard fashion is impossible. If this occurs, squeezing the sides of the locking button (located immediately above the pump chamber) allows the fluid to return to the pump chamber by circumventing the delay-fill resistor.

Preoperative details: During the informed consent, potential complications unique to this procedure should be discussed. Potential complications include urethral injury, bladder injury, mechanical failure, and persistent stress incontinence. The possibility of surgical revision at a future date also should be discussed.

The operating room staff, as well as the surgeon, should be familiar with the device, the equipment needed, and the surgical steps of the procedure. It is helpful for the surgeon and/or the operating room staff to observe the AMS 800 prosthesis implant procedure before surgery.

Prophylactic antibiotics should be administered, and the surgical team should scrub for 10 minutes prior to commencing with the operation.

Intraoperative details: Once the patient is in the operating room, the abdomen and genitalia are shaved. Following the shave, the area is scrubbed with povidone-iodine soap for 10 minutes. For bulbous urethra cuff placement, the patient is placed in the lithotomy position. The patient is draped for both a perineal and an abdominal incision.

A plastic-draped Mayo stand is used as a station for handling and filling of prosthetic components. The surgical setup should include a broad-spectrum antibiotic solution for irrigation. The antibiotic solution and the filling solution should be kept separate from each other. Components should not have contact with paper or cloth drapes. Submerge the filled components in a storage basin containing sterile sodium chloride solution until they are ready for implantation.

Silicone components actively attract dust and lint. Glove powder that enters the tubing may block the pump valves. Surgeons should wash their gloves before making the tubing connections. The operative technique of placing the urethral cuff is described below.

  • Balloon reservoir placement: Make a suprapubic incision. A midline or transverse incision is made. Divide the rectus fascia. Spread the linea alba to reach the prevesical space. Use blunt dissection to create a space for the balloon. Fill the balloon with 22 cc of the iso-osmotic filling solution, aspirate the air, and evacuate the fluid from the balloon. Clamp the tubing and position the balloon in the prevesical space. Route the tubing through the rectus fascia to the abdominal incision.

  • Bulbous cuff placement

    • Place a 14F Foley catheter. Make a midline perineal incision. Identify the bulbocavernosus muscle. The bulbocavernosus muscle is split in the midline and retracted laterally. Use a right angle clamp to dissect around the bulbar urethra under direct vision. Dissect out a 2-cm plane posteriorly around the urethra to accommodate the cuff. Encircle a Penrose drain around the urethra and use it as a retractor to facilitate urethral dissection. Exchange the Penrose drain for a measuring tape. The urethral measuring tape is placed around the urethra at the site where the cuff is to be implanted. The measuring tape must fit snugly without constricting the urethra. Remove the urethral catheter before measuring the urethra.

    • Select the cuff size that corresponds to the measured length. The cuff is prepared for implantation by injecting the filling solution into the cuff, aspirating all of the air, and then evacuating the fluid from the cuff. Place the cuff around the urethra. Pass the cuff, tab first, under the urethra. Snap the cuff into place. Route the cuff tubing suprapubically to the abdominal incision. Reapproximate the bulbocavernosus muscle over the cuff followed by Colles fascia. Close the perineal incision.

  • Pressurizing the system

    • To pressurize the cuff, the cuff tubing and the balloon tubing are temporarily connected using a straight connector. Remove the catheter. Flush the tubing ends to remove all debris. Fill the balloon with 22 cc of iso-osmotic filling solution. Temporarily connect the cuff tubing and the balloon tubing using a straight connector. This allows the cuff to pressurize. Wait 10-30 seconds. Clamp the cuff tubing and the balloon tubing with silicone-shod hemostats and remove the connector. Remove the hemostat and aspirate all of the remaining fluid from the balloon. Refill it with 20 cc of filling solution. Clamp the tubing with silicone-shod hemostat until the final connection is made. This 2-step filling compensates for the potential pressure atrophy.

    • In this author's opinion, pressurizing the cuff and the balloon reservoir prior to making the final connection is optional and is not truly necessary. This author does not perform this step but simply fills the pressure reservoir with 23 mL of isotonic sodium chloride solution (ie, 22 mL for the balloon and 1 mL for the cuff = total of 23 mL) and connects all the tubings after all components (ie, balloon, cuff, pump) have been implanted. By not pressuring the cuff, the operation is simplified without compromising the efficacy of the sphincter function.

  • Pump implantation: To implant the control pump in the scrotum use blunt dissection to create a dependent subdartos pouch. The control pump should be placed on the same side where the pressure-regulating balloon was placed. From the abdominal incision, dissect out the right hemiscrotum for pump placement. After filling the pump with filling solution, replace it in the scrotum. Place the pump in the most dependent part of the scrotal pouch, making sure that it is palpable and the locking button faces outward. The pump tubing should be above the rectus muscle and fascia in the abdominal incision.

  • Connections: After the components are placed, trim the excess tubing. Connect the ends of the tubing using the sutureless Quick connectors. Suture-tie connectors are used for revision surgeries. Connecting tubings should lie above the rectus fascia.

  • Checking the device: After the connections, the sphincter is cycled. At the authors' institution, retrograde perfusion sphincterometry with flexible cystoscopy is performed to check the integrity of the implanted sphincter. After confirming the sphincter is working properly, the cuff is locked in an open position (deactivated). To deactivate the device, the pump is squeezed and released several times to empty the cuff. When the cuff has refilled so that a slight dimple appears in it, the deactivation button is pushed to lock the cuff open. During the healing process, the cuff must remain locked in an open position. The abdominal incision is closed. A small Foley catheter (ie, 14F) is placed.

Postoperative details: Intravenous antibiotics are continued until discharge. The Foley catheter is removed the day after the surgery. The patients usually are discharged within 24-48 hours. At the authors' institution, oral antibiotics are prescribed for 2 weeks after discharge.

Immediately after implantation, a 6- to 8-week deactivation period allows healing. The cuff is left open in a locked state. Postoperatively, the patient experiences preoperative stress incontinence until the sphincter is activated. Thus, some protection must be used in the form of pads, external condom drainage, or intermittent catheterization during the healing phase.

Intermittent catheterization is not a contraindication to an artificial urinary sphincter as long as the cuff remains deflated. Those with bladder-neck cuff placement may perform self-catheterization without risk to the cuff and the underlying tissue. However, patients with bulbous urethral cuffs are at higher risk for injury from prolonged catheterization.

Follow-up care: The patient is instructed not to manipulate the sphincter for 6 weeks. The first postoperative clinic visit is in 1-2 weeks, at which time the abdominal and perineal incisions are inspected for skin integrity and wound infection. At 6-week follow-up, the sphincter is activated by applying a firm, forceful squeeze to the control pump. The patient is instructed on the proper use of this device by the physician and videotape.

All patients require direct visual demonstration of sphincter use after activation. Some patients are more adept than others in learning how to operate the pump. Improper cuff use is the most common cause of postactivation urinary incontinence. Patients experience incomplete emptying and overflow incontinence if the cuff is not opened properly. Lack of education or difficulty manipulating the pump leads to inadequate cuff deflation and sphincter malfunction.

If these patients are treated in the emergency department or if they require hospitalization for a medical problem, they are instructed to inform their treating physician that they have an artificial urinary sphincter. Passage of a catheter or any other instrument through the urethra without deflating the cuff and deactivating the device first may result in sphincter injury.

Patient Education:

For excellent patient education resources, visit eMedicine's Procedures Center. Also, see eMedicine's patient education article Cystoscopy.

  COMPLICATIONS  

The AMS 800 device

See Limitations of the AMS 800 under Treatment for a discussion of device-related complications.

Intraoperative complications

  • Infection: Because artificial urinary sphincter is a synthetic device, it is at risk of bacterial infection. The most common infecting organism is Staphylococcus epidermidis. Other pathogens include Proteus species, Pseudomonas species, Escherichia coli, Serratia species, Corynebacterium, and Enterobacter species. Meticulous aseptic techniques must be exercised during sphincter implantation. Perioperative antibiotics with gram-positive bacteria coverage are imperative. Traffic in the operating room must be minimized. After surgical implantation, prophylactic antibiotic coverage is recommended for patients undergoing any dental procedure.

  • Pressure-regulating balloon: The balloon reservoir is placed intra-abdominally or in an extraperitoneal prevesical space (space of Retzius). For patients with prior pelvic surgery, scars and adhesions increase the risk of bladder perforation. Iatrogenic peritoneotomy and bowel injury has been reported. If bowel injury occurs, the implantation must be abandoned.

  • Inflation cuff

    • Urethral injuries result from direct perforation or tissue necrosis due to thermal injury. Most urethral injuries occur at the 12 o'clock position, where the urethra is adherent to the corpus cavernosa. This is the most difficult site of dissection. Unrecognized urethral injuries result in early cuff erosion and incontinence. Bulbar placement in a prepubescent male should not be performed because the tissues are thin and the risk of erosion is high. Cuff implantation at the bladder neck is more difficult than at the bulbar urethra.

    • In females, a correct plane between the bladder neck and vagina must be identified to avoid injury to the urethra, vagina, and rectum. To aid in the cuff placement, the use of Cutter clamp and cystoscopy have been employed. Some surgeons open the bladder prior to dissection in order to visualize ureteral orifices and the bladder neck. Vaginal injuries are closed primarily. If a rectal injury occurs, the procedure must be abandoned.

  • Connecting tubing: The presence of particulate matters in the tubing increases the risk of sphincter malfunction. A few air bubbles entering the system are harmless because they are absorbed. However, aggregation of air bubbles into an air lock can obstruct the pump. Blood clots also can obstruct the connecting tube or the valves in the pump. Therefore, care is taken to prevent entry of particulate matter into the system by flushing the air bubble/blood clot out of tubing during surgery.

Postoperative complications

  • Tissue atrophy

    • A common cause of recurrent stress incontinence is loss of cuff compression due to tissue atrophy. Tissue atrophy has been reported as the most common cause of surgical revision, occurring in as may as 33-39% of cases in the literature (Gundian, 1989; Goldwasser, 1987). Martins and Boyd (1995) reported that inadequate cuff compression after presumed urethral atrophy accounted for 74% (ie, 60 out of 81 cases) of the recurrent stress incontinence in artificial urinary sphincters placed after a major pelvic surgery and/or radiation.

    • Tissue atrophy results from local tissue ischemia around the cuff. Tissue atrophy, in turn, causes poor mucosal coaptation and incomplete urethral occlusion. When the cuff inflates and deflates normally yet the patient remains incontinent, tissue atrophy should be suspected. The patient may notice the need to squeeze the pump more often to deflate the cuff. Usually, symptoms of tissue atrophy manifest approximately 4 months after initial device activation.

    • In 1987, a new narrow backed cuff was introduced to decrease the incidence of tissue atrophy. By decreasing the width of the outer leaflet from 2 to 1.5 cm while maintaining the inner leaflet dimension of at 2 cm, cuff pressure transmission to the urethra was improved. This modification allowed the inner cuff leaflet to compress a wider surface area without increasing the occlusive pressure. This new innovative design has decreased the reoperation rate to 0-9%.

    • Another method of retarding tissue atrophy is nocturnal deactivation of the cuff. The cuff is locked in an open position during the night when the patient is asleep. Nocturnal deactivation of the device has been reported to reduce tissue atrophy by decreasing the potential ischemia time.

    • If tissue atrophy occurs, balloon pressure can be increased to the next higher pressure (ie, from 61-70 to 71-80 cm H2O) to increase the urethral closing pressure. If this fails, the cuff can be downsized to a next smaller size or double cuffs may be placed. Alternatively, the cuff site may be changed to a different area with better tissue integrity.

  • Cuff erosion

    • The most feared complication of artificial urinary sphincter is cuff erosion. Cuff erosion most commonly occurs within 3-4 months after surgery. Early cuff erosion suggests unrecognized injury to the bladder neck or urethra at the time of surgery. Erosion also may occur as a result of periprosthetic infection or pressure necrosis. The site of erosion can be localized by urethroscopy; cuff protrusion through the urethral mucosa is unmistakably visible. The incidence of cuff erosion has been reported to be 0-19%. The most significant risk factor for delayed cuff erosion is pelvic radiation. The incidence of erosion is 10-20% in irradiated patients.

    • Efforts to minimize the incidence of cuff erosion include delayed activation, nocturnal deactivation, and use of a low-pressure reservoir. Delayed cuff activation has led to a 6% erosion rate with AMS 800 models. Nocturnal deactivation has been felt to reduce the risk of erosion. Using a balloon with a pressure less than 71-80 cm H2O also decreases the risk.

    • Early signs of erosion include gross hematuria, burning perineal pain, and swelling at the cuff site. If the erosion is clean and uncomplicated, only the cuff may be removed. A new cuff may be placed 3-6 months later. If purulent drainage is obvious, removal of all sphincter units is mandatory.

    • Women of childbearing age should be warned of the danger of cuff erosion during abdominal delivery. As the baby crowns through the vaginal introitus, the baby's head may compress the cuff against the pubic symphysis, risking cuff erosion. Elective cesarean delivery or deactivation of the artificial urinary sphincter in the final trimester is recommended to minimize the risk of cuff erosion in this situation.

Troubleshooting the AMS 800

  • Radiographic studies

    • Radiologic evaluation is an important means of troubleshooting a malfunctioning sphincter if contrast is used as a filling medium. Radiograph of the lower abdomen is the single most important test to obtain if contrast is present. If isotonic sodium chloride solution is used as fluid medium, radiographic evaluation does not help because silicone components are not radio-opaque.

    • Inflate-deflate radiographs are needed to assess the function of the sphincter. When the cuff is open, the pump and the balloon reservoir should contain some contrast, and the cuff should have none. When the cuff is closed, a doughnutlike circumferential ring of contrast should be visible at the cuff site. If the radiographic contrast is absent, leak has occurred.

  • Urethral pressure profilometry: Urethral pressure profilometry is a nonradiologic test of sphincter function. Withdrawal urethral pressure profilometry should be conducted with the cuff in both inflated and deflated modes. Minimal pressure differential between 2 modes suggests sphincter malfunction.

  • Perfusion sphincterometry: Retrograde perfusion sphincterometry with cystoscopy is a useful test to assess the integrity of the sphincter unit. If time to inflate the cuff is longer than usual or the urethra remains open, either cuff malfunction or tissue atrophy has occurred. At the authors' institution, retrograde perfusion sphincterometry with a flexible cystoscope is performed routinely at the time of sphincter implantation.

  • Electrical conductance testing: Reoperation often is required to service the malfunctioning device. At the time of operation, the use of electrical conductance testing (ohmmeter) aids in identifying the faulty component and the site of leak. Leaks at connector sites and the balloon stem are excluded first. If the ohmmeter cannot be used to identify the leak site, the pressure in the balloon reservoir can be measured by connecting the tubing to a pressure transducer or by aspirating and measuring the volume in the balloon.

  OUTCOME AND PROGNOSIS  

American Medical Systems (AMS, the manufacturer of the artificial urinary sphincter) has placed over 15,000 artificial urinary sphincters in men and women. The AMS 800 allows over 80% of patients to be completely continent and over 90% to be socially dry. The current rate of revisions varies from 0.3-0.6%. Patients who benefit most are those who can empty their urinary bladder and do not need intermittent catheterization.

  FUTURE AND CONTROVERSIES  

Placement of an artificial urinary sphincter (AMS 800) is an excellent surgical treatment for men, women, and children with type III stress urinary incontinence. Extremely reliable and durable, it has greatly improved quality of life for those patients plagued by SUI. For men who are incontinent postprostatectomy, the AMS 800 device is the only therapy that provides a consistently lasting cure for stress incontinence.

Despite recent advances in mechanical design, certain limitations exist with this device. When mechanical malfunctions and surgical problems arise, repeat surgery often is diagnostic and therapeutic. With continued advances in biomechanical engineering, an even better artificial urinary sphincter that approaches the function of a biological urinary sphincter should be forthcoming.

Insertion of an artificial urinary sphincter in a female patient is controversial. The long-term success rates of female artificial urinary sphincter placement have been reported to be 86-88% in the European literature (Heitz, 1997; Marques, 1999). However, implantation of the AMS 800 device in a female patient is fraught with potential complications that include vaginal, bladder, and urethral perforations. Additional complications include urethral erosion or wound infection necessitating device removal. Due to alternative effective surgical options such as pubovaginal sling or periurethral injection therapy, implantation of artificial urinary sphincter in an incontinent female is rarely performed in the United States.

The presence of recurrent vesical neck contracture in combination with postprostatectomy stress incontinence is a difficult problem to treat. Recurrent bladder neck contractures often are treated with incision (direct vision internal urethrotomy [DVIU]) or transurethral incision (TUIVNC) followed by implantation of an artificial urinary sphincter. Alternatively, intermittent catheterization is advocated to allow the contracture to "soften-up" and stabilize over time. After the contracture has stabilized, an artificial urinary sphincter may be placed. The exact timing of sphincter placement is tailored to each individual. Recently, Elliott et al (2001) have reported their positive experience with staged artificial urinary sphincter placement after incision of vesical neck contracture followed by UroLume stent.

  PICTURES  

Caption: Picture 1. Artificial urinary sphincter (AMS 800) is composed of pressure-balloon reservoir, inflate-deflate cuff, and miniature control pump.
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Caption: Picture 2. Artificial urinary sphincter. Patient is placed in dorsolithotomy position. Perineal incision has been made below the scrotum. Colles fascia is being dissected off.
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Caption: Picture 3. Artificial urinary sphincter. Bulbocavernosus muscle has been dissected off. The bulbar urethra is exposed.
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Caption: Picture 4. Artificial urinary sphincter. The right angle is passed behind the bulbar urethra.
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Caption: Picture 5. Artificial urinary sphincter. The measuring tape is passed around the bulbar urethra. The bulbar urethra measures 4.5 cm; thus, a 4.5-cm cuff is chosen for implantation.
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Caption: Picture 6. The artificial urinary sphincter cuff is passed, the tab end first, around the urethra. The cuff is snapped into place.
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Caption: Picture 7. The tab of the artificial urinary sphincter cuff is rotated dorsally.
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Caption: Picture 8. Artificial urinary sphincter. The cuff is seated in an excellent position. The tubing from the cuff is passed up to the suprapubic wound where it is connected to the control pump.
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Caption: Picture 9. Artificial urinary sphincter. The perineal incision is being closed. The Colles fascia is closed. The skin is closed next.
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Caption: Picture 10. Artificial urinary sphincter. The balloon reservoir has been placed into the subrectus space, and the control pump has been inserted into the right hemiscrotum. The connecting tubes, meaning the cuff, pump, and reservoir, are all connected.
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  BIBLIOGRAPHY  

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  • Barrett DM, O'Sullivan DC, Malizia AA: Particle shedding and migration from silicone genitourinary prosthetic devices. J Urol 1991 Aug; 146(2): 319-22.
  • Choe JM, Staskin DR: Artificial urinary sphincter: evolution and development. J Long Term Eff Med Implants 1997; 7(1): 75-100.
  • Choe JM: Freedom Regained: Female Urinary Incontinence Can Be Overcome. Columbus, Ohio: Anadem Publishing; 1999: 199-201.
  • Diokno AC, Hollander JB, Alderson TP: Artificial urinary sphincter for recurrent female urinary incontinence: indications and results. J Urol 1987 Oct; 138(4): 778-80.
  • Elliott DS, Boone TB: Combined stent and artificial urinary sphincter for management of severe recurrent bladder neck contracture and stress incontinence after prostatectomy: a long-term evaluation. J Urol 2001 Feb; 165(2): 413-5.
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  • Light JK, Reynolds JC: Impact of the new cuff design on reliability of the AS800 artificial urinary sphincter. J Urol 1992 Mar; 147(3): 609-11.
  • Marques Queimadelos A, Abascal Garcia R, Muruamendiaraz Fernandez V: [Artificial sphincter implantation in women with urinary incontinence using a combined abdomino-vaginal approach]. Arch Esp Urol 1999 Oct; 52(8): 877-80.
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  • Meulen T, Zambon JV, Janknegt RA: Treatment of anastomotic strictures and urinary incontinence after radical prostatectomy with urolume wallstent and AMS 800 artificial sphincter. J Endourol 1999 Sep; 13(7): 517-20.
  • Rose SC, Hansen ME, Webster GD: Artificial urinary sphincters: plain radiography of malfunction and complications. Radiology 1988 Aug; 168(2): 403-8.
  • Salisz JA, Diokno AC: The management of injuries to the urethra, bladder or vagina encountered during difficult placement of the artificial urinary sphincter in the female patient. J Urol 1992 Nov; 148(5): 1528-30.
  • Scott FB, Bradley WE, Timm GW: Treatment of urinary incontinence by implantable prosthetic sphincter. Urology 1973 Mar; 1(3): 252-9.
  • Shires GT, Canizaro PC: Fluid, Electrolyte, and Nutritional Management of the Surgical Patient. In: Schwartz SI, Lillehei RC, Shires GT, et al, eds. Principles of Surgery. 2nd ed. New York, NY: McGraw-Hill; 1974: 65.
  • Webster GD, Sihelnik SA: Troubleshooting the malfunctioning Scott artificial urinary sphincter. J Urol 1984 Feb; 131(2): 269-72.

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