Factors determining the outcome following implantation of the AMS 800 artificial urinary sphincter

Erosion and infection are major complications following implantation of the AMS 800 artificial urinary sphincter. In the present study, 17 patients with this prosthesis were investigated urodynamically. All were continent. Urethral pressure profilometry showed a significantly lower intra-urethral pressure than would have been expected from the pressure installed in the pressure regulating balloon during operation. The maximal urethral pressure was 69.9% of the expected pressure and did not vary significantly in relation to the various balloon pressures. The mean maximal urethral pressure (+/- SEM) between the cuff when inflated and when deflated was also significantly different, although the absolute difference was small (14.1 cm H2O +/- 10.0). There was good correlation between maximal urethral pressure and urethral leakage pressure as measured by retrograde perfusion sphincterometry. The mean functional urethral length became significantly longer after implantation of the cuff. A combination of low urethral pressure and increased functional length may help to prevent cuff erosion and maintain continence.     

Urethral pressure variations

The pressure in the area of distal urethral sphincter was measured in 30 patients with symptoms of stress, urge, and mixed stress and urge incontinence. Sphincteric pressures were obtained from 3 to 4 urethral pressure profiles and recordings of the pressure measured with the sensor placed at the site of the distal sphincter for periods of up to ten minutes. In 33 per cent of the patients, the latter method revealed significant pressure variations which rarely were seen in a small series of urethral pressure profiles. The diagnostic reliability of the urethral pressure profile with respect to pressure variations is discussed, and the spatial organization of the pressure variations is measured and discussed.     

Prognostic value of urodynamic testing in myelodysplastic patients

We herein describe the clinical progress of 42 myelodysplastic patients studied urodynamically and followed for a mean of 7.1 years. Urodynamic evaluation included urethral pressure profilometry, simultaneous determination of urethral pressure, intravesical pressure and external anal or external urethral sphincter electromyography with fluoroscopic voiding cystourethrography. Assessment of urethral function showed 36 patients (86 per cent) with an open vesical outlet and nonfunctional proximal urethra. Cystometrography revealed that 7 of 42 patients (17 per cent) had reflex detrusor activity: 4 with coordinated micturition and 3 with detrusorsphincter dyssynergia. Thirty-five patients (83 per cent) had areflexic detrusor dysfunction: 5 with atonic detrusor response and 30 with a progressive increase in pressure with increasing volume. The intravesical pressure at the time of urethral leakage was 40 cm. water or less in 20 patients and at pressures greater than this value in 22 patients. No patient in the low pressure group had vesicoureteral reflux and only 2 showed ureteral dilatation on excretory urography. In contrast, of the patients in the higher pressure group 15 (68 per cent) showed vesicoureteral reflux and 18 (81 per cent) showed ureteral dilatation on excretory urography. Thus, a striking relationship between the urethral closure pressure and intravesical pressure at the time of urethral leakage and the clinical course in this group of myelodysplastic patients is demonstrated. Every patient with a normally closed vesical outlet was continent on intermittent catheterization and an anticholinergic agent, while only 60 per cent of patients with open bladder outlets similarly treated achieved good urinary control and none was dry. An artificial sphincter device would seem to be a reasonable method to achieve urinary control in the latter patients but the detrusor response to filling also must be considered. Detrusor hypertonia should be controlled or controllable before a sphincter augmenting device can be used safely. Treatment options for patients with high urethral closure pressures include intermittent catheterization and anticholinergic medications or a sphincter ablative procedure to decrease the outlet resistance combined with anticholinergic therapy and implantation of an artificial sphincter. However, only longer followup will determine if these therapeutic regimens will prevent upper urinary tract deterioration.     

Experience with the artificial urinary sphincter model AS800 in 148 patients

The latest version of the artificial urinary sphincter, AS800, was used in 148 patients with urinary incontinence of different etiologies. Followup ranged from 3 to 37 months, with an average of 20.8 months. There were 112 (76 per cent) male and 36 (24 per cent) female patients. The cuff was implanted around the bladder neck in 78 patients (53 per cent) and around the bulbar urethra in 70 (47 per cent). Socially acceptable urinary control was achieved in 90 per cent of the 139 patients with active devices in place. It was necessary to remove the sphincter in 11 patients (7.4 per cent). The reasons for removal were infection and erosion in 8 patients (5.4 per cent), infection without erosion in 2 (1.3 per cent), and erosion due to excess pressure and poor tissues in 1 (0.7 per cent). Comparison of success and failure rates associated with incontinence of different etiologies revealed that patients with incontinence after failure of a conventional antistress incontinence operation and those with incontinence after transurethral resection or radical prostactectomy had the highest success rate, and that patients with incontinence secondary to pelvic fracture or exstrophy and epispadias had the highest failure rates. The deactivation feature (the lock) of the new artificial sphincter model was beneficial for primary deactivation, urethral catheterization or cystoscopy, or for elective nocturnal decompression of the bladder neck or urethral tissues.     

Treatment of urinary incontinence with an artificial sphincter: further experience with the AS791/792 device

Artificial sphincter models AS791 and AS792 were used to treat 36 male and 7 female patients with urinary incontinence. Satisfactory results were obtained in 72 per cent of the patients. Of 100 surgical procedures performed to achieve these results 61 were planned procedures (initial implantation and delayed activation) and 39 were revisions required to improve continence, change mechanically failing devices or remove eroded sphincters. From our study 3 major problems with the artificial sphincter are apparent: 1) stress incontinence, which was present in 55 per cent of the patients with bulbous urethral sphincter compared to 21 per cent with sphincters located at the bladder neck, 2) erosions, which appear to be related to balloon pressure used and location of the artificial sphincter (there seems to be a higher incidence of erosions when the bulbous urethral site is used with balloon pressure greater than 80 cm. water) and 3) mechanical failures of the device, which accounted for 41 per cent of the unplanned operations in our series. These 3 major problems are reviewed, the possible etiology of persistent stress incontinence is discussed and possible ways to avoid these complications are suggested.     

"Flowsecure" artificial urinary sphincter: a new adjustable artificial urinary sphincter concept with conditional occlusion for stress urinary incontinence

IntroductionTo spread de concept of a new artificial urinary sphincter with conditional occlusion for stress incontinence. The new prototype was conceived and designed in The Institute of Urology and Nephrology of London by Professor Craggs M. and Professor Mundy A.R.MethodsThe FlowSecure sphincter consists of an adjustable pressure-regulating balloon, a stress relief reservoir, a control pump and valve assembly unit with self-sealing port and a urethral cuff. The pressure regulating balloon determinates de operating pressure of the device; the pressure is adjustable in the range 0-80 cm H2O and can be altered by injection or removal of normal saline through the self sealing port. The stress relief balloon transmits transient intrabdominal pressure to the cuff during periods of stress. An adjustable circular urethral cuff minimises creasing and possible stress fractures.ResultsThe device is implanted as a one-piece assembly which is pre-filled with sterile saline. The surgical technique is simple and associated with little handling, reducing risk of infection and potential assembly errors. The adjustable pressure regulating balloon in association with the stress relief reservoir enables the cuff occluding pressure to be set at a low range, therefore reducing the risk for atrophy and erosion.DiscussionThe new FlowSecure urinary artificial sphincter with conditional occlusion is designed to provide good continence rates adjusting regulating pressures when needed and conceived to reduce the risk of potential complications associated with excessive occluding pressures and mechanical failures.     

The model AS 800 artificial urinary sphincter: Mayo Clinic experience

The model AS 800 artificial urinary sphincter was implanted in 100 male and 9 female patients between 7 and 89 years old. Postoperative followup was 1 to 32 months. The indication for implantation was total urinary incontinence in 86 patients (78.9 per cent), stress incontinence in 22 (21.2 per cent) and urgency incontinence in 1 (0.9 per cent). Of the patients 97 (89 per cent) underwent implantation for the first time, 7 (6.4 per cent) had a previous artificial urinary sphincter model replaced by the AS 800 device and 5 (4.6 per cent) underwent reimplantation of a previous model. The cuff was placed around the bladder neck in all 9 female patients, whereas in the male patients the cuff was implanted around the bladder neck in 20 and around the bulbous urethra in 80. Thirty-one patients (28.4 per cent), 29 of whom were continent at night, were practicing nocturnal deactivation of the device. Complete post-activation continence was achieved in 91 patients (83.5 per cent), some leakage occurred in 10 (9.2 per cent) and 8 (7.3 per cent) remained incontinent. A total of 23 patients required 1 or more revisions, the most common indications for the first revision being loss of cuff compression (9), tubing kink (3), cuff erosion (3) and infection (2). At the time of this report 89 patients (81.7 per cent) were continent, 9 (8.3 per cent) still had some leakage, 3 (2.8 per cent) were incontinent, 5 (4.6 per cent) were awaiting reimplantation and 3 (2.8 per cent) had died of unrelated causes.     

Management of urinary incontinence in women with the artificial urinary sphincter

This study concerns 39 women who underwent implantation of the artificial urinary sphincter for severe, persistent urinary incontinence following surgical correction of the anatomical deformity. The cause of incontinence was poor or absent function of the urethral sphincteric mechanism. The success rate in this series with the artificial urinary sphincter was 92 per cent. The condition of the tissues in the cuff area is crucial for success of the procedure. Some technical considerations of the procedure are discussed.     

The use of the AMS-AS800 artificial sphincter for continent urinary diversion. I. Investigations, including pressure-flow studies, using rabbit intestinal loops

The AS 800 genitourinary artificial sphincter was implanted in 40 New Zealand rabbits to evaluate its possible use for continent urinary diversion. This evaluation included the effects of varying closing pressures of the cuff implanted around isolated bowel loops. Six-weeks postoperative investigations included pressure/flow studies, autopsies, microangiographies and histologic evaluations. The sphincter was able to achieve continence during perfusion of the intestinal loop, maximum pressures being dependent on cuff pressures. Consistent changes were: 1) the formation of a thin fibrous capsule around the subcutaneously implanted pump, 2) the development of a fibrous sheath around the bowel beneath the cuff, and 3) fibrous and peritoneal reactions at the cuff site. In uncomplicated cases, the bowel wall tolerated the cuff pressure well, without macroscopic signs of atrophy. However, sphincter-related complications (1. infection, 2. erosion, 3. reduction of bowel circumference beneath the cuff) were pressure dependent and seen mainly in high pressure groups. Based on these results, the application of the sphincter for continent urinary diversion should include: low pressure urinary reservoirs, low pressure cuffs and most essentially, strict avoidance of infection.     

The urethral pressure profile at rest: An analysis of variance

Resting urethral pressure protile measurements were carried out by a microtransducer method on 100 women with a variety of urinary symptoms in an attempt to analyse the repeatability and reproducibility of the various protile parameters. The findings were as follows: The repeatability of parameters was shown to have some dependence on the rate of catheter withdrawal. being optiinal at 15 cm per minute. Profiles recorded by microtransducer showed greater consistency than those recorded by a fluid perfusion method. in terms of the parameters of urethral length. Whilst the fluid perfusion method has previously been shown to have a significant component of variance duc to time. no such time-dependent component was found with the microtransducer method. Urethral pressures measured by microtransducer do appear to have a significant time-dependence when recorded during the menstrual cycle in women of reproductive age. These findings suggest that the microtransducer method of urethral pressure measurement has a greater diagnostic reliability than the tluid perfusion method. It also has a greater capacity to assess the effects of drugs. hormones. and surgery on the urethral pressure profile. Care must be takcn. however. in the interpretation of pressure variations noted In women in reproductive age groups.     

Urethral pressure — which one?

Summary Urethral pressure was investigated by a method which allowed simultaneous measurement of the crosssectional area. In healthy women a pressure range of 25–140 cm H₂O was recorded at one urethral site as a response to the circumstances under which the measurement was performed. The pressures obtained were related to the change in distension. Measuring urethral pressure at one specific degree of distension results in one specific pressure value according to the dimensions of the measuring probe. However, this specific pressure value cannot be considered to supply more information on urethral sphincter function than any other pressures included in a range which can be obtained by changing the circumstances under which the measurement are carried out. More provocative methods of pressure measurement which simulate some of the physiological conditions of the urethra may provide more information on sphincter efficiency.     

Manometric assessment of an artificial bowel sphincter

BACKGROUND: This study investigated the relationship between functional clinical results after artificial bowel sphincter implantation and manometric assessment in 12 consecutive patients. METHODS: A postoperative manometric study was performed in 12 patients, including measurement of resting and squeeze pressures, opening characteristics and pressure during straining. The relationship between postoperative findings, clinical outcome and preoperative manometric data was investigated. Anal pressure after rectal distension with a closed cuff was studied in seven patients. Results were expressed as mean(s.d.). RESULTS: Continence for solid stool was achieved in all 12 patients. Five patients remained incontinent for gas. Anal resting pressure was 108(22) cmH2O; there was no difference between continent and incontinent patients. Rectal distension induced anal relaxation in six of seven patients. Total duration of cuff opening was 113(8) s with an amplitude of 60(22) per cent; residual pressure was correlated with the preoperative resting pressure. The total duration of the opening phase in patients with defaecation difficulties (47(24) (range 0-65) s) was shorter than that in patients without defaecation difficulties (178(78) (range 100-320) s) (P = 0.0022). CONCLUSION: Postoperative defaecation difficulties after implantation of an artificial bowel sphincter are related to a short duration of opening of the cuff. The anal sphincter played a role in postoperative resting anal pressures and allowed relaxation even if the cuff was closed.     

Artificial urinary sphincter for recurrent female urinary incontinence: indications and results

A retrospective review of our experience with the artificial urinary sphincter in 32 women is presented. All patients had a history of recurrent urinary incontinence after failed bladder suspension procedures. Of 32 devices 31 were functioning, with an average followup of 2.5 years, and 91 per cent of the patients were dry without pads. Mechanical complications requiring surgical repair occurred in 21 per cent of the patients. Indications for artificial urinary sphincter implantation in the female patient and technical aspects of the procedure are discussed. The artificial urinary sphincter appears to be an acceptable treatment modality for urethral sphincter deficiency resulting in recurrent urinary stress incontinence in female patients.     

Urethral atrophy after artificial urinary sphincter placement: is cuff downsizing effective?

PURPOSE: We reviewed the outcome of cuff downsizing with an artificial urinary sphincter for treating recurrent incontinence due to urethral atrophy. MATERIALS AND METHODS: We analyzed the records of 17 patients in a 7-year period in whom clinical, radiological and urodynamic evidence of urethral atrophy was treated with cuff downsizing. Cuff downsizing was accomplished by removing the existing cuff and replacing it with a 4 cm. cuff within the established false capsule. Incontinence and satisfaction parameters before and after the procedure were assessed by a validated questionnaire. RESULTS: Mean patient age was 70 years (range 62 to 79). Average time to urethral atrophy was 31 months (range 5 to 96) after primary sphincter implantation. Mean followup after downsizing was 22 months (range 1 to 64). Cuff downsizing caused a mean decrease of 3.9 to 0.5 pads daily. The number of severe leakage episodes decreased from a mean of 5.4 to 2.1 The mean SEAPI (stress leakage, emptying, anatomy, protection, inhibition) score decreased from 8.2 to 2.4. Patient satisfaction increased from 15% to 80% after cuff downsizing. In 1 patient an infected cuff required complete removal of the device. CONCLUSIONS: Patient satisfaction and continence parameters improved after cuff downsizing. We believe that this technique is a simple and effective method of restoring continence after urethral atrophy.     

Interaction phenomena between a cuff of an artificial urinary sphincter and a urethral phantom

Male urinary incontinence is highly prevalent, leading to a miserable quality of life. The artificial urinary sphincter (AUS) is the device that closely simulates the function of the biological urinary sphincter. The precise evaluation of occlusion mechanisms and of interaction phenomena occurring between AUS cuff and urethral duct is fundamental for more reliable design. The action induced in the interaction with urethral duct under a specific pressure depends on its constitutive material and structural characteristics. The methods of experimental and computational bioengineering are exploited to investigate mechanical functionality of the coupled system, as AUS and urethral duct. Experimental tests are developed to investigate the response when the AUS is inflated around a urethral phantom. Numerical model of the cuff is developed mimicking the experimental tests for the validation. Subsequently, numerical models are exploited to interpret the interaction of the cuff with urethral phantoms considering the influence of urethral size and of tissues mechanical behavior, mimicking healthy and degraded configurations. The investigation provides useful information on the behavior of AUS cuff with urethral duct evaluating the action induced and represents a support for planning an extension of experimental tests on animal and human urethral samples.     

Uneven pressure application by the artificial urinary sphincter: an explanation for tissue ischaemia?

OBJECTIVE: To determine, in an in vitro study, the pressure inside the AMS 800 (American Medical Systems, USA) sphincter placed around porcine intestine and to correlate this with the pressure retention for liquids, in an attempt to explain the increased sensitivity of bowel to ischaemic injury when the artificial urinary sphincter is used around bowel neo-urethral segments. MATERIALS AND METHODS: Segments of porcine intestine were placed in a specially designed mechanical jig and an AMS 800 sphincter placed around the segment. The device was inflated by injecting water and the cuff pressure measured. Water was infused into the bowel and the pressure at which leakage occurred through the sphincter recorded. At each inflation pressure, a catheter-tipped microtransducer was used to measure the pressure inside the cuff-fold. It was then placed in the centre of the cuff lumen, rotated by 360 degrees and the pressure continuously recorded. RESULTS: The cuff occluded the lumen by creating a 'triple-cushion' effect. The fluid retention pressure was 49% of the cuff pressure. There were directional differences in the pressure measured inside the bowel lumen. The pressure was also disproportionately higher inside the cuff folds than in the centre of the sphincter, and increased rapidly with inflation of the cuff. CONCLUSION: The thin wall of the bowel may 'crenate' inside the high-pressure areas in the cuff folds and this may explain the increased sensitivity of bowel to ischaemic injury in such cases.     

Sex Differences in the Determination of Abdominal Leak Point Pressure in Patients with Intrinsic Sphincter Deficiency

Purpose

We determined the effect of a urethral catheter on abdominal leak point pressure in men and women with intrinsic sphincter deficiency.

Materials and Methods

A total of 21 consecutive men treated with prostatectomy and 19 women with intrinsic sphincter deficiency underwent abdominal leak point pressure measurements with a rectal catheter before and after removal of a 10F urethral catheter.

Results

Of the 19 women 2 had leakage only when the urethral catheter was removed, while 17 had excellent correlation between abdominal leak point pressures before and after catheter removal (r = 0.83). In contrast, 10 of 21 men had leakage only when the urethral catheter was removed and 11 had weak correlation between abdominal leak point pressures before and after catheter removal (r = 0.46).

Conclusions

An indwelling 10F urethral catheter is much more likely to invalidate abdominal leak point pressure measurement in men than in women with intrinsic sphincter deficiency.     

Addition of a Second Urethral Cuff to Enhance Performance of the Artificial Urinary Sphincter

Purpose

Stress urinary incontinence may persist in approximately 15 percent of men following implantation of a standard artificial urinary sphincter. The ability of a second urethral cuff to provide satisfactory continence without additional operative complications was investigated.

Materials and Methods

A second urethral cuff was placed to enhance performance of the artificial urinary sphincter in 5 men with stress urinary incontinence following radical prostatectomy. A stainless steel 3-way tubing connector allowed for addition of a second cuff to the standard artificial urinary sphincter without the kinking problems previously observed with a flexible 3-way connector. In 4 consecutive men a second cuff was added at operative revision of an existing artificial urinary sphincter that had failed to produce satisfactory continence. A double cuff artificial sphincter was placed initially in 1 man.

Results

Of 5 men 4 had satisfactory and 1 had improved continence with the double cuff artificial urinary sphincter. The stainless steel 3-way tubing connector eliminated kinking complications.

Conclusions

Implantation of a second urethral cuff can provide satisfactory urinary continence in men with an artificial urinary sphincter and persistent incontinence. Placement of a double cuff artificial urinary sphincter may also represent appropriate initial intervention in men with significant stress urinary incontinence.     

Urodynamic Assessment of Urethral Sphincter Function In Post-Prostatectomy Incontinence

Purpose

Direct measurement of maximum urethral pressure by urethral profilometry has been used widely to assess urethral sphincter function. We attempted to determine if there was any relationship between maximum urethral pressure, which is measured at the level of the membranous urethra, or extrinsic urethral sphincter function, and the amount of abdominal pressure needed to cause leakage (abdominal leak point pressure) in men with post-prostatectomy incontinence. We also examined the relationship between external sphincter function and continence or incontinence.

Materials and Methods

We retrospectively evaluated fluoro-urodynamics performed in 37 men with post-prostatectomy incontinence. Urodynamic study consisted of measurement of maximum urethral and abdominal leak point pressures, and assessment of extrinsic sphincter function by pressure measurements and radiographically.

Results

Data were analyzed on 27 patients for whom abdominal leak point and maximum urethral pressures were available. Mean maximum urethral pressure was 52.5 cm. water (range 20 to 165) and mean abdominal leak point pressure was 77.8 cm. water (range 27 to 132). Regression analysis was performed between maximum urethral and abdominal leak point pressures. A Pearson correlation coefficient of 0.13834 was calculated (p = 0.4914) indicating virtually no correlation between the 2 measurements in our sample. Extrinsic urethral sphincter was normal in all patients. Only 1 of 37 patients had no evidence of intrinsic sphincter deficiency, that is there was no urine leakage with increases in abdominal pressure and the patient was incontinent solely based on bladder dysfunction (detrusor instability).

Conclusions

Our study indicates that incontinence after prostatectomy due to an increase in abdominal pressure (stress incontinence) does not depend on extrinsic sphincter function and is not related to maximal urethral pressure. We conclude that post-prostatectomy incontinence due to sphincter dysfunction results from intrinsic sphincter deficiency. In our experience bladder dysfunction is rarely the sole cause of post-prostatectomy incontinence.     

The role of low urethral mucosal and submucosal blood perfusion in patients with artificial urinary sphincters

IntroductionA common complication following insertion of a bulbar AUS is recurrent incontinence, and once other causes have been ruled out, a diagnosis of urethral atrophy is then made. Urethral atrophy probably occurs to a certain degree in all patients with an AUS but the reappearance of incontinence is often attributed to inadequate pressure transfer from the cuff to the atrophic urethra. The normal urethral closure mechanism depends also on passive forces which rely on the integrity of the urethral mucosa and submucosa.Material and MethodsTwo groups of patients with a first AUS implant which had been in place for more than 1 year were studied (n=11). Group I consisted of continent patients (n_I=6) whereas Group II had significant incontinence due to urethral atrophy (n_II=5). Intraurethral pressures (IP) and blood flux (BF) were measured simultaneously with a micro-tip transducer and a laser Doppler flowmeter in each patient. Positional measurements were recorded proximal, within, and distal to the cuff first with the AUS deactivated and then activated.ResultsGroup I patients exhibited similar IP and BF at all positions along the urethra. In Group II the IP was similar along the urethra but the BF within the cuff was qualitatively different (non pulsatile) and decreased significantly when compared to either side of the cuff during.DiscussionContinence in patients with artificial urinary sphincters depends not only on the cuff occlusive force but is also dependent on the viability of the mucosal and submucosal tissues. For a given pressure range mucosal and submucosal blood perfusion is determinant: patients with normal blood perfusion would remain continent whereas patients with impaired perfusion would become incontinent.