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Genuine stress incontinence
Current Obstetrics & Gynaecology (2001) 11, 353^358
c 2001 Harcourt Publishers Ltd doi:10.1054/cuog.2001.0209 available online at http://www.idealibrary.com on
Genuine stress incontinence K. Lingam Rotherham District General Hospital, Moorgate Road, Oakwood, Rotherham S60 2UD, UK
KEYWORDS genuine stress incontinence, urethral hypermobility, intrinsic sphincter de¢ciency
Summary Stress incontinence is both a symptom and a sign.The diagnosis of genuine stress incontinence can only be made from urodynamic studies as they will show loss of urine during rise in intra-abdominal pressure in the absence of detrusor activity. Genuine stress incontinence (GSI) can be due to urethral hypermobility, intrinsic sphincter de¢ciency or both. Although surgery remains the mainstay of treatment for GSI, conservative therapy should be considered ¢rst.There are many di¡erenttypes of surgical operations that can be used in the treatment of GSI but surgery will depend on the type of incontinence, the patient’s ¢tness and the skill of the surgeon.
c 2001Harcourt Publishers Ltd
INTRODUCTION There is a one-in-three chance that any woman has a secret: incontinence. Many women do not seek help as they consider this as part of the price they pay for being mothers, part of the ageing process and also often feel afraid or embarrassed to seek help. The actual incidence of stress incontinence is not known but Thomas reported that the symptoms of stress incontinence were more common in the ages between 45 and 54, while urge incontinence was more common between 35 and 64 years. Kondo found the maximum prevalence of stress incontinence in the 50 -year age group. It has been estimated that 3 million people su¡er from incontinence in the United Kingdom, a prevalence of 40 per 1000 adults, costing the National Health Service around 424 million pounds per annum. Genuine stress incontinence (GSI) is de¢ned as the involuntary loss of urine when the intravesical pressure exceeds the maximal urethral closure pressure in the absence of detrusor activity.
PATHOPHYSIOLOGYOF GENUINE STRESS INCONTINENCE GSI could be due to urethral hypermobility, intrinsic sphincter de¢ciency (ISD) or both. In urethral hypermobility, GSI results when the bladder neck and urethra fail to maintain a watertight seal at rest and under conditions of increased intra-abdominal pressure.The development of GSI is usually due to a combination of factors rather than the failure of a single mechanism. Mechanical trauma such as pregnancy, vaginal delivery and upright postures are major factors in the development of pelvic £oor weakness which can a¡ect resting intraurethral presCorrespondence to: KL.Tel: +01709 304610; fax: +01709 304318; E-mail:[email protected]
sure.Urethral pressure should be considered as a threshold level below which urine loss occurs when there is incomplete transmission of pressure to the urethra with stress. When patients with GSI are compared to controls, the mean resting urethral pressures are lower and the maximal urethral pressure tends to be lower with increasing severity of incontinence. Descent and mobility of the proximal urethra and the bladder base with stress are regarded as important aetiological factors of urethral sphincter incompetence.The basic anatomic defect appears to be loss of integrity of the vaginal musculofascial attachment that includes pubo-urethral ligaments and endopelvic fascia that normally supports the bladder neck and the urethra in a retropubic position. Defects in the support leads to hypermobility and descent of the structures resulting in impaired intra-abdominal pressure transmission to the urethra. This is essentially DeLancey’s hammock hypothesis for stress incontinence. Normally abdominal pressure forces the urethra against a stable supportive layer and keeps the urethra closed. However, when there is defective supportive tissue, this mechanism becomes ine¡ective in providing a resistant backstop against which the urethra can be compressed. Defects in this supportive mechanism are thought to arise from damage to nerves that control the pelvic £oor and periurethral muscles. Damage to the pudendal nerve during vaginal delivery can lead to weakness and atrophy of the medial portions of the levator ani muscles as well as the voluntary muscles of the perineum. This damage can then further predispose to vaginal support defects and to reduction in fast twitch re£ex pelvic muscle contraction, a factor that is thought to be involved in continence during stress. In ISD, the urethra no longer functions as a sphincter and cannot maintain a watertight seal even at rest.The bladder neck and urethra can be hypermobile or ¢xed and non-mobile. The causes of ISD are not completely known but are thought probably
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to be related to neuromuscular changes and damage seen with ageing and childbirth.The urethral muscles could be very lax or the urethral wall could be rigid and scarred. Either mechanism can lead to failure of urethral coaptation with an open bladder neck being seen at rest during radiological imaging. Patients with ISD are often severely incontinent, with leakage of urine seen on minimal exertion such as standing.The majority of primary GSI form a combination of bladder neck hypermobility and ISD. The exact pathophysiology of GSI remains unknown but the failure of pressure transmission remains the most popular theory.
DIAGNOSIS OF GSI A detailed history and examination of the patient is important. Examination must document the presence and severity of anterior vaginal relaxation including cystocele, proximal urethral detachment, mobility and any associated uterovaginal prolapse. A Q-tip test which involves the placement of a cotton swab in the urethra to the level of the bladder neck and the measurement of axis change during straining can be used to demonstrate urethral hypermobility. The common signs on physical examination are anterior vaginal wall relaxation, urethral hypermobility and observed loss of urine on coughing. As most women with primary GSI have urethral hypermobility, a negative test should cause you to question the diagnosis. The measurement of urethral hypermobility should not be used to di¡erentiate the urethral sphincter incompetence from abnormalities of voiding or detrusor function because these diagnoses require measurement of detrusor pressure during ¢lling and voiding. A midstream specimen of urine should be sent for culture to exclude infection. A frequency^volume chart can also provide valuable information such as voiding pattern, £uid intake and output as often patient histories are inaccurate and misleading. Stress incontinence is a symptom i.e. the patient complains of urinary leakage when intra-abdominal pressure is increased during activity. Stress incontinence is also a sign i.e. urine leakage noted during examination of the patient. Therefore, stress incontinence is not pathognomonic of GSI as it can often be demonstrated in patients with detrusor instability or over£ow incontinence. The diagnosis of GSI can only be made after urodynamics assessment. It is important to distinguish GSI from the symptom of stress incontinence which may be due to other causes. It has been recognized that symptoms tend to correlate poorly with a de¢nitive diagnosis made on urodynamic assessment. Why should it be that we need urodynamics to make the diagnosis of GSI? Normally, prior to detrusor contraction there is urethral relaxation. The sphincter therefore cannot be said to be incompetent if it is relaxed. It is therefore important to exclude detrusor activity before GSI can be reported.The absence in the rise
CURRENT OBSTETRICS & GYNAECOLOGY
of the detrusor pressure to ful¢ll the de¢nition of GSI can only be seen during urodynamic studies.For this reason, GSI can only be accurately diagnosed from urodynamic studies. In one study 12% of women with symptoms of only stress incontinence were shown to have detrusor instability rather than GSI as the cause of their symptoms. Patients with combined GSI and detrusor overactivity could still have surgery but it has been shown that in the presence of preoperative detrusor instability, surgical outcome is poorer when compared to those patients with pure GSI. Furthermore, if the patient’s symptoms of stress incontinence are due to detrusor instability (DI), then GSI surgery in the absence of anatomical defect could potentially worsen the detrusor instability. Urodynamics can provide further information on urethral and detrusor function. This information may be useful when planning and giving advice regarding the surgical outcome. If DI is present surgery is not contraindicated but the patient must be warned that DI cannot be cured and may in fact make her DI worse. Information on urethral function can also be obtained. If the maximal urethral closure pressure is below 20 cm H2O, this is likely to indicate ISD and, therefore, retropubic operations such as colposuspension are not the operations of choice, a sling procedure being more appropriate. A low £ow rate with minimal or no detrusor pressure rise during voiding is indicative of an underactive detrusor. In these patients, surgery increases their risk of voiding dysfunction and they must be taught intermittent selfcatherization prior to surgery in the event that they develop post-operative voiding di⁄culties. In one study, it was shown that no patient who had detrusor pressures above 15 mm of H2O had voiding di⁄culties whilst 84% with detrusor pressure below15 mm H2O had prolonged voiding di⁄culties. It has now been accepted both clinically and medicolegally that preoperative urodynamic studies should be carried out in all patients who proceed to surgery. Since GSI is a diagnosis that is made only from urodynamics, should all patients have urodynamics? It has been shown that there is a poor correlation between signs, symptoms and urodynamics ¢ndings. Thus, even in the most typical situation diagnosis may be uncertain. This uncertainty may be acceptable if medical or conservative treatment is planned.This is because urodynamics is an invasive procedure that has its own morbidity. Urodynamics can also be carried out as video-urodynamics or ambulatory urodynamics. Indication for video-urodynamics is when both anatomical and physiological data are required. The group of patients that would bene¢t from video-urodynamics are those who have recurrent stress incontinence, suspected bladder outlet obstruction and neuropathic vesico-urethral dysfunction. In women who have failed incontinence surgery, video will provide information on the bladder neck position, bladder base support and function of the pelvic £oor. It will also demonstrate typically, patients with ISD who will
GENUINE STRESS INCONTINENCE
have an open rectangular shaped incompetent bladder neck. Lastly, an indication for ambulatory urodynamics is to con¢rm the patient’s history of incontinence where conventional urodynamics has been normal and to determine whether detrusor instability or sphincter weakness is the main cause of incontinence if the patients desires further treatment.
CONSERVATIVE MANAGEMENT OF GSI Although surgical treatment has been the mainstay of treatment for GSI, it is now recognized that conservative therapy should be considered prior to surgical options. Although the complete cure rate for conservative therapy is lower than surgical treatment, the satisfaction rate can be quite high. Conservative therapy is also indicated in patients who are un¢t for surgery, those who do not wish surgery or have not completed child bearing. Conservative therapy is relatively inexpensive without the morbidity that is seen with surgery. The di¡erent types of conservative therapy are the following.
Behavioural modi¢cation A frequency^volume chart can help identify patients with excess £uid intake and the modi¢cation of £uid intake can be recommended. Constipation is associated with urinary incontinence and therefore women should be advised to maintain a healthy bowel habit by increasing £uid and ¢bre intake. Many studies have found obesity to be an independent factor for stress incontinence. Weight loss should be encouraged in the obese patients.
Bladder retraining It has been shown that by patient education and scheduled voiding, there was a 57% reduction in incontinence episodes and a 54% reduction in the amount of £uid lost. The women are encouraged to void on schedule and relaxation techniques are used to suppress urge sensations.
Physiotherapy Since the bladder is supported by muscles of the pelvic £oor, physiotherapy in the form of pelvic £oor exercises can be helpful. It is unclear whether physiotherapy is successful because it re-educates muscle action or because it strengthen muscles. One study has shown no correlation between increased muscle bulk and decreased incontinence after a course of pelvic £oor exercises. Age, duration of incontinence and previous incontinence surgery have been shown to have positive predictive value for successful pelvic £oor treatment.
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The overall rate for cure or improvement is about 60% at 5-year follow-up.
Vaginal cones These are often used as an adjunct to pelvic £oor exercises. Vaginal weights provide a form of biofeed back treatment at home. The vaginal cones help patients become aware of the pelvic £oor. The cones are retained in the vagina both by passive and active contraction of the pelvic £oor. Graduation of the weights of the cones from 20 to 100 g lets the patient know that progress is being made. A 70% cure rate has been reported with vaginal cones, although another single-blind randomized study showed pelvic £oor exercises to be superior both to vaginal cones and electrical stimulation.
Electrical stimulation In research settings, intravaginal electrical stimulation augments urethral sphincteric function and inhibits bladder contractility. The technique involves pudendal nerve stimulation with electrodes placed in the vagina or anus. In one randomized placebo-controlled clinical trial, the number of incontinent episodes reduced by 50% in 48% of women using the active device and by only13% in those using placebo.
Drug therapy The bladder and urethra contain a rich supply of oestrogen receptors and also alpha-adrenoreceptors. Oestrogen promotes vaginal cellular maturation and bene¢cial vaginal £ora. Randomized studies report mixed results. Cardozo reported no greater subjective improvement but video-urethrography revealed signi¢cant improvement in bladder base descensus in women receiving oestrogen implants. Stimulation of the alpha-adrenoreceptors produces smooth muscle contraction causing increase in maximum urethral closure pressure and bladder outlet resistance. Several studies have shown bene¢ts in patients with mild-to-moderate symptoms but do not su⁄ciently improve severe symptoms of stress incontinence to o¡er as an alternative to surgical treatment.The use of oestrogen therapy has been shown to increase the number of alpha-adrenergic receptors and studies have shown that a combination therapy of oestrogen and alpha-adrenergic agents was superior to separate treatment.
Mechanical devices There are many di¡erent pessaries and vaginal devices to treat incontinence. Devices either elevate and support the bladder neck or occlude the urethra. A recent
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bladder neck prosthesis (Introl, Uromed, Needham, MA) showed a mean reduction in urinary leakage from 59.8 to 22.8 episode per week with improved quality of life score. However, side-e¡ects included urinary infection and vaginal soreness. The more recent urethral devices include urethral plug, urethral patch and urethral meatus suction cap. An 80% cure rate has been shown with intraurethral devices with a reported 25% urinary tract infection.
SURGICALTREATMENTOF GSI There are two main pathophysiological causes of GSI which are urethral hypermobility and ISD. It is important to be aware that both these conditions can exist in the same women. It is important to make the correct diagnosis ¢rst before surgery can be undertaken. In patients with urethral hypermobility, an operation to reposition the bladder neck will have a high success rate whilst in women who have ISD, failure will result as the bladder neck may already be in the optimal position. There are three main classes of operation for patients who have GSI secondary to urethral hypermobility. (1) Retropubic operations which include Burch colposuspension and Marshall ^Marchetti Krantz (MMK). These procedures yield the best results when the urethral sphincter is capable of maintaining a watertight seal at rest but cannot withstand the unequal transmission of abdominal pressure to the proximal urethra, relative to the bladder with straining. (2) Needle suspension which includes Stamey, Pereyra, Raz and Gittes operations. (3) Vaginal operations such as Kelly’s procedures. The Burch colposuspension is the best studied retropubic procedure. Eighteen studies between 1980 and 1990 looked at patients with urodynamic-proven GSI who had Burch colposuspension. A continence rate of 59^100% with an overall cure rate of 84% has been shown at 3^24 months after surgery. At 3^7 years continence rates range from 63%^ 89% with an average cure rate of 77%. The long-term cure rate is time dependent with a decline between10 and12 years and then a plataeu at 69%. Approximately 10% of patients required at least one additional operation to cure stress incontinence. In 1994, Jarvis reviewed studies after1970 for the treatment of GSI using objective outcomes. He noted that only MMK, Burch colposuspension, endoscopic bladder neck suspension and sling procedures produced continence rates above 85% for primary procedures. He also noted that average cure rates of only colposuspension and sling procedures have tight con¢dence intervals, implying that studies describing these procedures have yielded the most consistent results. Black and Downs published an excellent systematic review in 1996 of e¡ectiveness of
CURRENT OBSTETRICS & GYNAECOLOGY
surgery for GSI. There were only two randomized controlled trials. The di¡erent methods of performing colposuspension e.g. Burch colposuspension and MMK procedures were not shown to be associated with significant di¡erences in the outcomes. Colposuspension appears to be more e¡ective than anterior colporrhaphy and needle urethropexy procedures in curing and improving stress incontinence. About 85% of women can expect to be continent at 1 year compared to 50 ^70% after anterior colporrhaphy and needle suspension. The American Urological Association meta-analysis of the literature up to 1993 regarding surgical operation used to treat GSI has shown that after 48 months retropubic suspension and sling procedures are more e⁄cacious than transvaginal needle suspension or anterior colporrhaphy. They also noted that slings and retropubic procedures are associated with slightly higher complication rates, including longer convalescence and post-operative voiding dysfunction. Factors that a¡ect the outcome of surgery include obesity, menopause, prior hysterectomy and prior incontinence surgery. Age is an important factor as this is thought to be a combination of poorer healing and the normal loss of urethral closure pressure that occurs with age.Urodynamic ¢ndings that increase the risk of surgical failure include signs of intrinsic urethral sphincter de¢ciency, abnormal perineal electromyography and concurrent detrusor instability and also maximum urethral closure pressure of less than 20 cm of water in those patients with previous failed continence surgery. Wound complications and urinary tract infections are the most common immediate surgical complications. Other complications include direct surgical injury to the urinary tract, urethral obstruction, ¢stula and death. Voiding di⁄culties are not uncommon after retropubic procedures. It is seen particularly in patients with preoperative £ow rates less than 15 ml/s or maximum voiding detrusor pressure below 15 cm H2O. Between 12% and 25% of women report delay voiding post-operatively and 11^20% have increased residual volumes and a reduced £ow rate when measured post-operatively. Detrusor instability arises de novo in 12^18.5% of women undergoing colposuspension. This is thought to be due to preexisting detrusor instability not detected at cystometry preoperatively. Another mechanism that has been suggested is disruption of autonomic innervation of the bladder during surgery. Excessive urethral elevation or compression can lead to partial out£ow obstruction, resulting in detrusor instability. Osteitis pubis can occur after 0.74 ^2.5% MMK procedures. Enterocele and rectocele are seen to occur in between 7% and 17% of cases. There are three di¡erent operations for ISD. These include sling operations, injectable periurethral bulking agents and arti¢cial urinary sphincter. Continence is achieved with slings by two possible mechanisms. Firstly, restoration of the normal urethrovesical junction support
GENUINE STRESS INCONTINENCE
at rest and secondly by functioning as a backboard against which urethra is compressed during increased abdominal pressure. Increased out£ow resistance is created by upward displacement of the sling, with rectus muscle shortening during stress. These forces combine to produce closure of the bladder neck and functional continence. Slings can also be used for patients with urethral hypermobility and coexisting ISD. Some recommend that slings should be used as primary surgical procedures in women with anatomic GSI, but controversy still exists around their use in urethral hypermobility. Injectable periurethral bulking enhancing agents are another surgical option in patients with ISD. The mechanism of action is to coapt the urethral lumen at the bladder neck to recreate normal sphincteric competence and increase urethral closure pressures. They are best reserved for patients with a poorly functioning urethral sphincter with no evidence of urethral hypermobility. Their use in urethral hypermobility with or without ISD is controversial.They are very useful in patients who have had multiple failed incontinence surgeries and in patients who have had radiotherapy when the urethra is scarred and ¢xed. There are many di¡erent injectable materials and these include collagen, autologous fat, silicon polymer (Macroplastique), carbon particles, bone and ceramic materials and silicon balloons. Regardless of the material, the technique for injectables is the same either transurethrally or periurethrally. Injury to the bladder and urethra can occur with sling procedures, especially in those patients who have had previous surgery. Suburethral sling procedures are associated with a signi¢cant risk of voiding dysfunction and retention. This is because the procedure can signi¢cantly increase urethral outlet resistance. Retention after slings is seen in 2^10% of patients. It has now being recognized that slings should be placed loosely with not too much tension used if voiding problems are to be avoided. Post-operative detrusor instability with urgency and frequency occurs in between 2% and 50% of patients.This may be due to preexisting detrusor instability now unmasked, by increased bladder volumes caused by a return of out£ow resistance, or by de-novo instability due to infection, graft reaction, denervation or anatomic urethral obstruction. De-novo detrusor instability responds well to bladder retraining and anticholinergic therapy. There is a risk of infection and erosion of graft and this is more common with synthetic grafts. A small number of patients will need the graft removed and often there is also coexisting infection. There is now a growing trend to use autologous or donor-directed organic material for suburethral sling procedures.Treating the patient in the dorsal lithotomy position can result in nerve compression or stretch injuries. The most common nerve to be a¡ected is the common peroneal nerve. Surgical damage to the ilioinguinal nerve can occur during placement and tying of the
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sling material, in some cases needing surgical removal of the suture. Complications using injectables are uncommon. The incidence of urinary retention following the procedure ranges from 15%^25%. This usually resolves within 24 ^ 48 h. Post-operative de-novo detrusor instability is rare, although in one series it has been reported as high as 39%. Cure rates for slings range from 70% to 95%. Jarvis’s meta-analysis showed objective cure rates of 85.3% whilst that published by the American Urological Association reported an overall success rate of 82%. Success from injectables ranges from 70% to 100%, depending on the type and length of follow-up. In another meta-analysis of 15 studies with 528 patients, at 2 years 49% were cured and 67% were cured or improved.The variation in cure rates depends on the technique, type of material used, length of follow-up and type of incontinence treated.There are no randomized studies comparing the different materials used to date. Arti¢cial urinary sphincter (AMS800) is traditionally used in women with GSI secondary to poor urethral sphincteric function. It is not used as ¢rst-line treatment and most surgeons would use it when one or more surgical continence procedures have failed. This procedure is only undertaken in specialist centres as the technique of implantation is di⁄cult and mechanical failure can occur. Patients must be motivated and have the manual dexterity to manipulate the pump mechanism. It is a controlled obstruction, which is released during the time of micturition. It consists of a urinary sphincter cu¡, a pressure regulating balloon, a control pump and tubing. The control pump is placed in the labia majora. The balloon is placed in the retropubic space and the cu¡ placed around the bladder neck. When the patient wishes to void, she squeezes on the pump, which transfers £uid to the balloon. When she releases the pump, £uid is sucked back from the cu¡ into the balloon. The process is repeated until the pump goes £at, signifying that the cu¡ is de£ated. The patient then voids and the balloon automatically repressurises, ¢lling the cu¡ up. Three minutes are required to ¢ll the cu¡, thus allowing the patients to have adequate time to void. In expert hands success can be high. In one series of 32 patients, 91% success was reported, with mechanical complications requiring repair occurring in 21% of these patients. In a more recent series of 34 patients, a100% cure rate was reported with no case of infection or erosion. Mundy, Stepheson and Stanton have also reported good results.
RECENT DEVELOPMENTS IN SURGICALTREATMENT FOR GSI Tension-free vaginal tape is a new operation for GSI which is based on the model that it is not the bladder
358
neck but the failure of the pubourethral ligament which causes incontinence. The tension-free vaginal tape aims to restore the pubourethral ligament and suburethral vaginal hammock by using specially designed needles attached to synthetic sling material made of knitted prolene mesh tape. Currently, there is a large randomized controlled study comparing theTVTwith open colposuspension in the United Kingdom and Europe. Complications from TVT have been reported and these include bladder injuries in up to 8%, rare problems include vascular injuries and long-term voiding problems. Ulmsten, who designed this tape, reports an 86% subjective cure after 3 years. Other centres have also reported success with the procedures with 88% subjective cure as a primary procedure and 75% as secondary procedures. The advantage of laparoscopic surgery has been the low morbidity and the short hospital stay with early return to work.This advantage has been exploited to treat incontinence. Several laparoscopic procedures have been published and they include both extraperitoneal and transperitoneal approaches. Material used have included standard sutures, prolene, mersilene mesh and clips. Several reports have now been published demonstrating the poor long-term outcome. The most recent randomized trial between open and laparoscopic Burch showed a 40% failure rate in the laparoscopic group compared to 15% in the open group. Ureteric injuries are more common in the laparoscopic group when compared to the open group.There is a long learning curve for this procedure and this might account for the results seen. However, with the current evidence available the open Burch colposuspension remains the superior operation. There is an ongoing MRC prospective randomized trial of laparoscopic vs open Burch colposuspension which
PRACTICE POINTS . GSI is the involuntary loss of urine when the intravesical pressure exceeds the maximum urethral pressure in the absence of detrusor
CURRENT OBSTETRICS & GYNAECOLOGY
.
.
.
.
activity Stress incontinence is both a symptom and a sign but is not pathognomic of GSI GSI can only be accurately diagnosed from urodynamic studies. This is because one needs to show that there is urethral relaxation in the absence of detrusor activity Conservative treatment should be o¡ered to all patients as ¢rst-line treatment. When conservative therapy has failed, then surgical treatment can produce good results There are many di¡erent surgical treatment for GSI. Treatment should be tailored to the type of incontinence, the patient’s ¢tness and the skill of the surgeon Successful treatment of incontinence should be based on a multidisciplinary team approach with both conservative and surgical treatment options available to the patient
should de¢ne the place of laparoscopic surgery in the treatment of incontinence.
FURTHER READING DeLancey J. Structural support of the urethra as it relates to stress urinary incontinence: the hammock hypothesis. Am J Obstet Gynaecol 1994; 170: 1713^1723. Blavias J G, Olsson C A. Stress incontinence: classi¢cation and surgical approach. J Urol 1998; 39: 727^731. Jarvis G J. Surgery for stress incontinence. Br J Obstet Gynaecol 1994; 101: 371^374. Black N A, Downs S H. The e¡ectiveness of surgery for stress incontinence in women: a systematic review Br J Urol 1996; 78: 497^510. Jarvis G J. Stress incontinence. In: Mundy A R, StephensonT P, Wein A J. (eds) Urodynamics; Principles, Practice & Application, 2nd edition. New York: Churchill Livington,1994; 299^326. Leach G, Dmochowski R, Appell R, et al. Female stress urinary incontinence guidelines. Panel summary report on surgical management of female stress incontinence. J Urol 1997; 158: 875^ 880. Abrahms P. Urodynamics, 2nd edition. Berlin: Springer 1997. Cardozo L. Urogynaecology, 1st edition. London: Churchill Livingston, 1997. Walter M D, Karram M M. Urogynaecology and Reconstructive Pelvic Surgery, 2nd edition. Mosby, Missouri,1999.
c 2001 Harcourt Publishers Ltd doi:10.1054/cuog.2001.0209 available online at http://www.idealibrary.com on
Genuine stress incontinence K. Lingam Rotherham District General Hospital, Moorgate Road, Oakwood, Rotherham S60 2UD, UK
KEYWORDS genuine stress incontinence, urethral hypermobility, intrinsic sphincter de¢ciency
Summary Stress incontinence is both a symptom and a sign.The diagnosis of genuine stress incontinence can only be made from urodynamic studies as they will show loss of urine during rise in intra-abdominal pressure in the absence of detrusor activity. Genuine stress incontinence (GSI) can be due to urethral hypermobility, intrinsic sphincter de¢ciency or both. Although surgery remains the mainstay of treatment for GSI, conservative therapy should be considered ¢rst.There are many di¡erenttypes of surgical operations that can be used in the treatment of GSI but surgery will depend on the type of incontinence, the patient’s ¢tness and the skill of the surgeon.
c 2001Harcourt Publishers Ltd
INTRODUCTION There is a one-in-three chance that any woman has a secret: incontinence. Many women do not seek help as they consider this as part of the price they pay for being mothers, part of the ageing process and also often feel afraid or embarrassed to seek help. The actual incidence of stress incontinence is not known but Thomas reported that the symptoms of stress incontinence were more common in the ages between 45 and 54, while urge incontinence was more common between 35 and 64 years. Kondo found the maximum prevalence of stress incontinence in the 50 -year age group. It has been estimated that 3 million people su¡er from incontinence in the United Kingdom, a prevalence of 40 per 1000 adults, costing the National Health Service around 424 million pounds per annum. Genuine stress incontinence (GSI) is de¢ned as the involuntary loss of urine when the intravesical pressure exceeds the maximal urethral closure pressure in the absence of detrusor activity.
PATHOPHYSIOLOGYOF GENUINE STRESS INCONTINENCE GSI could be due to urethral hypermobility, intrinsic sphincter de¢ciency (ISD) or both. In urethral hypermobility, GSI results when the bladder neck and urethra fail to maintain a watertight seal at rest and under conditions of increased intra-abdominal pressure.The development of GSI is usually due to a combination of factors rather than the failure of a single mechanism. Mechanical trauma such as pregnancy, vaginal delivery and upright postures are major factors in the development of pelvic £oor weakness which can a¡ect resting intraurethral presCorrespondence to: KL.Tel: +01709 304610; fax: +01709 304318; E-mail:[email protected]
sure.Urethral pressure should be considered as a threshold level below which urine loss occurs when there is incomplete transmission of pressure to the urethra with stress. When patients with GSI are compared to controls, the mean resting urethral pressures are lower and the maximal urethral pressure tends to be lower with increasing severity of incontinence. Descent and mobility of the proximal urethra and the bladder base with stress are regarded as important aetiological factors of urethral sphincter incompetence.The basic anatomic defect appears to be loss of integrity of the vaginal musculofascial attachment that includes pubo-urethral ligaments and endopelvic fascia that normally supports the bladder neck and the urethra in a retropubic position. Defects in the support leads to hypermobility and descent of the structures resulting in impaired intra-abdominal pressure transmission to the urethra. This is essentially DeLancey’s hammock hypothesis for stress incontinence. Normally abdominal pressure forces the urethra against a stable supportive layer and keeps the urethra closed. However, when there is defective supportive tissue, this mechanism becomes ine¡ective in providing a resistant backstop against which the urethra can be compressed. Defects in this supportive mechanism are thought to arise from damage to nerves that control the pelvic £oor and periurethral muscles. Damage to the pudendal nerve during vaginal delivery can lead to weakness and atrophy of the medial portions of the levator ani muscles as well as the voluntary muscles of the perineum. This damage can then further predispose to vaginal support defects and to reduction in fast twitch re£ex pelvic muscle contraction, a factor that is thought to be involved in continence during stress. In ISD, the urethra no longer functions as a sphincter and cannot maintain a watertight seal even at rest.The bladder neck and urethra can be hypermobile or ¢xed and non-mobile. The causes of ISD are not completely known but are thought probably
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to be related to neuromuscular changes and damage seen with ageing and childbirth.The urethral muscles could be very lax or the urethral wall could be rigid and scarred. Either mechanism can lead to failure of urethral coaptation with an open bladder neck being seen at rest during radiological imaging. Patients with ISD are often severely incontinent, with leakage of urine seen on minimal exertion such as standing.The majority of primary GSI form a combination of bladder neck hypermobility and ISD. The exact pathophysiology of GSI remains unknown but the failure of pressure transmission remains the most popular theory.
DIAGNOSIS OF GSI A detailed history and examination of the patient is important. Examination must document the presence and severity of anterior vaginal relaxation including cystocele, proximal urethral detachment, mobility and any associated uterovaginal prolapse. A Q-tip test which involves the placement of a cotton swab in the urethra to the level of the bladder neck and the measurement of axis change during straining can be used to demonstrate urethral hypermobility. The common signs on physical examination are anterior vaginal wall relaxation, urethral hypermobility and observed loss of urine on coughing. As most women with primary GSI have urethral hypermobility, a negative test should cause you to question the diagnosis. The measurement of urethral hypermobility should not be used to di¡erentiate the urethral sphincter incompetence from abnormalities of voiding or detrusor function because these diagnoses require measurement of detrusor pressure during ¢lling and voiding. A midstream specimen of urine should be sent for culture to exclude infection. A frequency^volume chart can also provide valuable information such as voiding pattern, £uid intake and output as often patient histories are inaccurate and misleading. Stress incontinence is a symptom i.e. the patient complains of urinary leakage when intra-abdominal pressure is increased during activity. Stress incontinence is also a sign i.e. urine leakage noted during examination of the patient. Therefore, stress incontinence is not pathognomonic of GSI as it can often be demonstrated in patients with detrusor instability or over£ow incontinence. The diagnosis of GSI can only be made after urodynamics assessment. It is important to distinguish GSI from the symptom of stress incontinence which may be due to other causes. It has been recognized that symptoms tend to correlate poorly with a de¢nitive diagnosis made on urodynamic assessment. Why should it be that we need urodynamics to make the diagnosis of GSI? Normally, prior to detrusor contraction there is urethral relaxation. The sphincter therefore cannot be said to be incompetent if it is relaxed. It is therefore important to exclude detrusor activity before GSI can be reported.The absence in the rise
CURRENT OBSTETRICS & GYNAECOLOGY
of the detrusor pressure to ful¢ll the de¢nition of GSI can only be seen during urodynamic studies.For this reason, GSI can only be accurately diagnosed from urodynamic studies. In one study 12% of women with symptoms of only stress incontinence were shown to have detrusor instability rather than GSI as the cause of their symptoms. Patients with combined GSI and detrusor overactivity could still have surgery but it has been shown that in the presence of preoperative detrusor instability, surgical outcome is poorer when compared to those patients with pure GSI. Furthermore, if the patient’s symptoms of stress incontinence are due to detrusor instability (DI), then GSI surgery in the absence of anatomical defect could potentially worsen the detrusor instability. Urodynamics can provide further information on urethral and detrusor function. This information may be useful when planning and giving advice regarding the surgical outcome. If DI is present surgery is not contraindicated but the patient must be warned that DI cannot be cured and may in fact make her DI worse. Information on urethral function can also be obtained. If the maximal urethral closure pressure is below 20 cm H2O, this is likely to indicate ISD and, therefore, retropubic operations such as colposuspension are not the operations of choice, a sling procedure being more appropriate. A low £ow rate with minimal or no detrusor pressure rise during voiding is indicative of an underactive detrusor. In these patients, surgery increases their risk of voiding dysfunction and they must be taught intermittent selfcatherization prior to surgery in the event that they develop post-operative voiding di⁄culties. In one study, it was shown that no patient who had detrusor pressures above 15 mm of H2O had voiding di⁄culties whilst 84% with detrusor pressure below15 mm H2O had prolonged voiding di⁄culties. It has now been accepted both clinically and medicolegally that preoperative urodynamic studies should be carried out in all patients who proceed to surgery. Since GSI is a diagnosis that is made only from urodynamics, should all patients have urodynamics? It has been shown that there is a poor correlation between signs, symptoms and urodynamics ¢ndings. Thus, even in the most typical situation diagnosis may be uncertain. This uncertainty may be acceptable if medical or conservative treatment is planned.This is because urodynamics is an invasive procedure that has its own morbidity. Urodynamics can also be carried out as video-urodynamics or ambulatory urodynamics. Indication for video-urodynamics is when both anatomical and physiological data are required. The group of patients that would bene¢t from video-urodynamics are those who have recurrent stress incontinence, suspected bladder outlet obstruction and neuropathic vesico-urethral dysfunction. In women who have failed incontinence surgery, video will provide information on the bladder neck position, bladder base support and function of the pelvic £oor. It will also demonstrate typically, patients with ISD who will
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have an open rectangular shaped incompetent bladder neck. Lastly, an indication for ambulatory urodynamics is to con¢rm the patient’s history of incontinence where conventional urodynamics has been normal and to determine whether detrusor instability or sphincter weakness is the main cause of incontinence if the patients desires further treatment.
CONSERVATIVE MANAGEMENT OF GSI Although surgical treatment has been the mainstay of treatment for GSI, it is now recognized that conservative therapy should be considered prior to surgical options. Although the complete cure rate for conservative therapy is lower than surgical treatment, the satisfaction rate can be quite high. Conservative therapy is also indicated in patients who are un¢t for surgery, those who do not wish surgery or have not completed child bearing. Conservative therapy is relatively inexpensive without the morbidity that is seen with surgery. The di¡erent types of conservative therapy are the following.
Behavioural modi¢cation A frequency^volume chart can help identify patients with excess £uid intake and the modi¢cation of £uid intake can be recommended. Constipation is associated with urinary incontinence and therefore women should be advised to maintain a healthy bowel habit by increasing £uid and ¢bre intake. Many studies have found obesity to be an independent factor for stress incontinence. Weight loss should be encouraged in the obese patients.
Bladder retraining It has been shown that by patient education and scheduled voiding, there was a 57% reduction in incontinence episodes and a 54% reduction in the amount of £uid lost. The women are encouraged to void on schedule and relaxation techniques are used to suppress urge sensations.
Physiotherapy Since the bladder is supported by muscles of the pelvic £oor, physiotherapy in the form of pelvic £oor exercises can be helpful. It is unclear whether physiotherapy is successful because it re-educates muscle action or because it strengthen muscles. One study has shown no correlation between increased muscle bulk and decreased incontinence after a course of pelvic £oor exercises. Age, duration of incontinence and previous incontinence surgery have been shown to have positive predictive value for successful pelvic £oor treatment.
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The overall rate for cure or improvement is about 60% at 5-year follow-up.
Vaginal cones These are often used as an adjunct to pelvic £oor exercises. Vaginal weights provide a form of biofeed back treatment at home. The vaginal cones help patients become aware of the pelvic £oor. The cones are retained in the vagina both by passive and active contraction of the pelvic £oor. Graduation of the weights of the cones from 20 to 100 g lets the patient know that progress is being made. A 70% cure rate has been reported with vaginal cones, although another single-blind randomized study showed pelvic £oor exercises to be superior both to vaginal cones and electrical stimulation.
Electrical stimulation In research settings, intravaginal electrical stimulation augments urethral sphincteric function and inhibits bladder contractility. The technique involves pudendal nerve stimulation with electrodes placed in the vagina or anus. In one randomized placebo-controlled clinical trial, the number of incontinent episodes reduced by 50% in 48% of women using the active device and by only13% in those using placebo.
Drug therapy The bladder and urethra contain a rich supply of oestrogen receptors and also alpha-adrenoreceptors. Oestrogen promotes vaginal cellular maturation and bene¢cial vaginal £ora. Randomized studies report mixed results. Cardozo reported no greater subjective improvement but video-urethrography revealed signi¢cant improvement in bladder base descensus in women receiving oestrogen implants. Stimulation of the alpha-adrenoreceptors produces smooth muscle contraction causing increase in maximum urethral closure pressure and bladder outlet resistance. Several studies have shown bene¢ts in patients with mild-to-moderate symptoms but do not su⁄ciently improve severe symptoms of stress incontinence to o¡er as an alternative to surgical treatment.The use of oestrogen therapy has been shown to increase the number of alpha-adrenergic receptors and studies have shown that a combination therapy of oestrogen and alpha-adrenergic agents was superior to separate treatment.
Mechanical devices There are many di¡erent pessaries and vaginal devices to treat incontinence. Devices either elevate and support the bladder neck or occlude the urethra. A recent
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bladder neck prosthesis (Introl, Uromed, Needham, MA) showed a mean reduction in urinary leakage from 59.8 to 22.8 episode per week with improved quality of life score. However, side-e¡ects included urinary infection and vaginal soreness. The more recent urethral devices include urethral plug, urethral patch and urethral meatus suction cap. An 80% cure rate has been shown with intraurethral devices with a reported 25% urinary tract infection.
SURGICALTREATMENTOF GSI There are two main pathophysiological causes of GSI which are urethral hypermobility and ISD. It is important to be aware that both these conditions can exist in the same women. It is important to make the correct diagnosis ¢rst before surgery can be undertaken. In patients with urethral hypermobility, an operation to reposition the bladder neck will have a high success rate whilst in women who have ISD, failure will result as the bladder neck may already be in the optimal position. There are three main classes of operation for patients who have GSI secondary to urethral hypermobility. (1) Retropubic operations which include Burch colposuspension and Marshall ^Marchetti Krantz (MMK). These procedures yield the best results when the urethral sphincter is capable of maintaining a watertight seal at rest but cannot withstand the unequal transmission of abdominal pressure to the proximal urethra, relative to the bladder with straining. (2) Needle suspension which includes Stamey, Pereyra, Raz and Gittes operations. (3) Vaginal operations such as Kelly’s procedures. The Burch colposuspension is the best studied retropubic procedure. Eighteen studies between 1980 and 1990 looked at patients with urodynamic-proven GSI who had Burch colposuspension. A continence rate of 59^100% with an overall cure rate of 84% has been shown at 3^24 months after surgery. At 3^7 years continence rates range from 63%^ 89% with an average cure rate of 77%. The long-term cure rate is time dependent with a decline between10 and12 years and then a plataeu at 69%. Approximately 10% of patients required at least one additional operation to cure stress incontinence. In 1994, Jarvis reviewed studies after1970 for the treatment of GSI using objective outcomes. He noted that only MMK, Burch colposuspension, endoscopic bladder neck suspension and sling procedures produced continence rates above 85% for primary procedures. He also noted that average cure rates of only colposuspension and sling procedures have tight con¢dence intervals, implying that studies describing these procedures have yielded the most consistent results. Black and Downs published an excellent systematic review in 1996 of e¡ectiveness of
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surgery for GSI. There were only two randomized controlled trials. The di¡erent methods of performing colposuspension e.g. Burch colposuspension and MMK procedures were not shown to be associated with significant di¡erences in the outcomes. Colposuspension appears to be more e¡ective than anterior colporrhaphy and needle urethropexy procedures in curing and improving stress incontinence. About 85% of women can expect to be continent at 1 year compared to 50 ^70% after anterior colporrhaphy and needle suspension. The American Urological Association meta-analysis of the literature up to 1993 regarding surgical operation used to treat GSI has shown that after 48 months retropubic suspension and sling procedures are more e⁄cacious than transvaginal needle suspension or anterior colporrhaphy. They also noted that slings and retropubic procedures are associated with slightly higher complication rates, including longer convalescence and post-operative voiding dysfunction. Factors that a¡ect the outcome of surgery include obesity, menopause, prior hysterectomy and prior incontinence surgery. Age is an important factor as this is thought to be a combination of poorer healing and the normal loss of urethral closure pressure that occurs with age.Urodynamic ¢ndings that increase the risk of surgical failure include signs of intrinsic urethral sphincter de¢ciency, abnormal perineal electromyography and concurrent detrusor instability and also maximum urethral closure pressure of less than 20 cm of water in those patients with previous failed continence surgery. Wound complications and urinary tract infections are the most common immediate surgical complications. Other complications include direct surgical injury to the urinary tract, urethral obstruction, ¢stula and death. Voiding di⁄culties are not uncommon after retropubic procedures. It is seen particularly in patients with preoperative £ow rates less than 15 ml/s or maximum voiding detrusor pressure below 15 cm H2O. Between 12% and 25% of women report delay voiding post-operatively and 11^20% have increased residual volumes and a reduced £ow rate when measured post-operatively. Detrusor instability arises de novo in 12^18.5% of women undergoing colposuspension. This is thought to be due to preexisting detrusor instability not detected at cystometry preoperatively. Another mechanism that has been suggested is disruption of autonomic innervation of the bladder during surgery. Excessive urethral elevation or compression can lead to partial out£ow obstruction, resulting in detrusor instability. Osteitis pubis can occur after 0.74 ^2.5% MMK procedures. Enterocele and rectocele are seen to occur in between 7% and 17% of cases. There are three di¡erent operations for ISD. These include sling operations, injectable periurethral bulking agents and arti¢cial urinary sphincter. Continence is achieved with slings by two possible mechanisms. Firstly, restoration of the normal urethrovesical junction support
GENUINE STRESS INCONTINENCE
at rest and secondly by functioning as a backboard against which urethra is compressed during increased abdominal pressure. Increased out£ow resistance is created by upward displacement of the sling, with rectus muscle shortening during stress. These forces combine to produce closure of the bladder neck and functional continence. Slings can also be used for patients with urethral hypermobility and coexisting ISD. Some recommend that slings should be used as primary surgical procedures in women with anatomic GSI, but controversy still exists around their use in urethral hypermobility. Injectable periurethral bulking enhancing agents are another surgical option in patients with ISD. The mechanism of action is to coapt the urethral lumen at the bladder neck to recreate normal sphincteric competence and increase urethral closure pressures. They are best reserved for patients with a poorly functioning urethral sphincter with no evidence of urethral hypermobility. Their use in urethral hypermobility with or without ISD is controversial.They are very useful in patients who have had multiple failed incontinence surgeries and in patients who have had radiotherapy when the urethra is scarred and ¢xed. There are many di¡erent injectable materials and these include collagen, autologous fat, silicon polymer (Macroplastique), carbon particles, bone and ceramic materials and silicon balloons. Regardless of the material, the technique for injectables is the same either transurethrally or periurethrally. Injury to the bladder and urethra can occur with sling procedures, especially in those patients who have had previous surgery. Suburethral sling procedures are associated with a signi¢cant risk of voiding dysfunction and retention. This is because the procedure can signi¢cantly increase urethral outlet resistance. Retention after slings is seen in 2^10% of patients. It has now being recognized that slings should be placed loosely with not too much tension used if voiding problems are to be avoided. Post-operative detrusor instability with urgency and frequency occurs in between 2% and 50% of patients.This may be due to preexisting detrusor instability now unmasked, by increased bladder volumes caused by a return of out£ow resistance, or by de-novo instability due to infection, graft reaction, denervation or anatomic urethral obstruction. De-novo detrusor instability responds well to bladder retraining and anticholinergic therapy. There is a risk of infection and erosion of graft and this is more common with synthetic grafts. A small number of patients will need the graft removed and often there is also coexisting infection. There is now a growing trend to use autologous or donor-directed organic material for suburethral sling procedures.Treating the patient in the dorsal lithotomy position can result in nerve compression or stretch injuries. The most common nerve to be a¡ected is the common peroneal nerve. Surgical damage to the ilioinguinal nerve can occur during placement and tying of the
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sling material, in some cases needing surgical removal of the suture. Complications using injectables are uncommon. The incidence of urinary retention following the procedure ranges from 15%^25%. This usually resolves within 24 ^ 48 h. Post-operative de-novo detrusor instability is rare, although in one series it has been reported as high as 39%. Cure rates for slings range from 70% to 95%. Jarvis’s meta-analysis showed objective cure rates of 85.3% whilst that published by the American Urological Association reported an overall success rate of 82%. Success from injectables ranges from 70% to 100%, depending on the type and length of follow-up. In another meta-analysis of 15 studies with 528 patients, at 2 years 49% were cured and 67% were cured or improved.The variation in cure rates depends on the technique, type of material used, length of follow-up and type of incontinence treated.There are no randomized studies comparing the different materials used to date. Arti¢cial urinary sphincter (AMS800) is traditionally used in women with GSI secondary to poor urethral sphincteric function. It is not used as ¢rst-line treatment and most surgeons would use it when one or more surgical continence procedures have failed. This procedure is only undertaken in specialist centres as the technique of implantation is di⁄cult and mechanical failure can occur. Patients must be motivated and have the manual dexterity to manipulate the pump mechanism. It is a controlled obstruction, which is released during the time of micturition. It consists of a urinary sphincter cu¡, a pressure regulating balloon, a control pump and tubing. The control pump is placed in the labia majora. The balloon is placed in the retropubic space and the cu¡ placed around the bladder neck. When the patient wishes to void, she squeezes on the pump, which transfers £uid to the balloon. When she releases the pump, £uid is sucked back from the cu¡ into the balloon. The process is repeated until the pump goes £at, signifying that the cu¡ is de£ated. The patient then voids and the balloon automatically repressurises, ¢lling the cu¡ up. Three minutes are required to ¢ll the cu¡, thus allowing the patients to have adequate time to void. In expert hands success can be high. In one series of 32 patients, 91% success was reported, with mechanical complications requiring repair occurring in 21% of these patients. In a more recent series of 34 patients, a100% cure rate was reported with no case of infection or erosion. Mundy, Stepheson and Stanton have also reported good results.
RECENT DEVELOPMENTS IN SURGICALTREATMENT FOR GSI Tension-free vaginal tape is a new operation for GSI which is based on the model that it is not the bladder
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neck but the failure of the pubourethral ligament which causes incontinence. The tension-free vaginal tape aims to restore the pubourethral ligament and suburethral vaginal hammock by using specially designed needles attached to synthetic sling material made of knitted prolene mesh tape. Currently, there is a large randomized controlled study comparing theTVTwith open colposuspension in the United Kingdom and Europe. Complications from TVT have been reported and these include bladder injuries in up to 8%, rare problems include vascular injuries and long-term voiding problems. Ulmsten, who designed this tape, reports an 86% subjective cure after 3 years. Other centres have also reported success with the procedures with 88% subjective cure as a primary procedure and 75% as secondary procedures. The advantage of laparoscopic surgery has been the low morbidity and the short hospital stay with early return to work.This advantage has been exploited to treat incontinence. Several laparoscopic procedures have been published and they include both extraperitoneal and transperitoneal approaches. Material used have included standard sutures, prolene, mersilene mesh and clips. Several reports have now been published demonstrating the poor long-term outcome. The most recent randomized trial between open and laparoscopic Burch showed a 40% failure rate in the laparoscopic group compared to 15% in the open group. Ureteric injuries are more common in the laparoscopic group when compared to the open group.There is a long learning curve for this procedure and this might account for the results seen. However, with the current evidence available the open Burch colposuspension remains the superior operation. There is an ongoing MRC prospective randomized trial of laparoscopic vs open Burch colposuspension which
PRACTICE POINTS . GSI is the involuntary loss of urine when the intravesical pressure exceeds the maximum urethral pressure in the absence of detrusor
CURRENT OBSTETRICS & GYNAECOLOGY
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activity Stress incontinence is both a symptom and a sign but is not pathognomic of GSI GSI can only be accurately diagnosed from urodynamic studies. This is because one needs to show that there is urethral relaxation in the absence of detrusor activity Conservative treatment should be o¡ered to all patients as ¢rst-line treatment. When conservative therapy has failed, then surgical treatment can produce good results There are many di¡erent surgical treatment for GSI. Treatment should be tailored to the type of incontinence, the patient’s ¢tness and the skill of the surgeon Successful treatment of incontinence should be based on a multidisciplinary team approach with both conservative and surgical treatment options available to the patient
should de¢ne the place of laparoscopic surgery in the treatment of incontinence.
FURTHER READING DeLancey J. Structural support of the urethra as it relates to stress urinary incontinence: the hammock hypothesis. Am J Obstet Gynaecol 1994; 170: 1713^1723. Blavias J G, Olsson C A. Stress incontinence: classi¢cation and surgical approach. J Urol 1998; 39: 727^731. Jarvis G J. Surgery for stress incontinence. Br J Obstet Gynaecol 1994; 101: 371^374. Black N A, Downs S H. The e¡ectiveness of surgery for stress incontinence in women: a systematic review Br J Urol 1996; 78: 497^510. Jarvis G J. Stress incontinence. In: Mundy A R, StephensonT P, Wein A J. (eds) Urodynamics; Principles, Practice & Application, 2nd edition. New York: Churchill Livington,1994; 299^326. Leach G, Dmochowski R, Appell R, et al. Female stress urinary incontinence guidelines. Panel summary report on surgical management of female stress incontinence. J Urol 1997; 158: 875^ 880. Abrahms P. Urodynamics, 2nd edition. Berlin: Springer 1997. Cardozo L. Urogynaecology, 1st edition. London: Churchill Livingston, 1997. Walter M D, Karram M M. Urogynaecology and Reconstructive Pelvic Surgery, 2nd edition. Mosby, Missouri,1999.