Stress urinary incontinence is a common condition that can severely affect a woman’s quality of life. Midurethral slings (tension-free vaginal tape and transobturator tape) are becoming first-line surgical treatments for stress urinary incontinence in women. Both procedures gained worldwide popularity immediately after they were introduced. Short operative time, brief hospitalization period, and ease of application have played a role in their acceptance. Sufficient data support the use of both retropubic and transobturator approaches for the placement of a midurethral sling. However, longer follow up in larger populations should assess the long-term reliability of these procedures.
Introduction
Stress urinary incontinence (SUI) is a non-life threatening condition that can be socially embarrassing and psychologically debilitating. It can affect a woman’s quality of life profoundly. The International Continence Society has defined urodynamic stress incontinence as the involuntary loss of urine during increased intra-abdominal pressure during filling cystometry, in the absence of a detrusor contraction. The prevalence of SUI is high, especially in postmenopausal women. Factors that may increase the risk of developing incontinence include obesity, straining at stool, heavy manual labour, chronic obstructive pulmonary disease, and smoking. Incidence increases with age. Over 100 surgical procedures have been described in the past century for the surgical treatment of SUI. Most of these procedures were potentially morbid, had poor long-term success rates, and most gynaecological surgeons had limited experience of them. With painstaking efforts of Petros and Ulmsten, and the advent of minimally invasive mid-urethral sling procedures in the mid 1990s, gynaecologists and urogynacologists became more enthusiastic about undertaking these simple and effective vaginal procedures. Currently, mid-urethral sling procedures are considered to be ‘gold standard’ operations for the treatment of SUI. In this review, I focus only on surgical procedures through the vaginal route.
Historical perspective and evolution
The idea of elevating the bladder neck and urethra for the treatment of SUI was known since the beginning of the 20th century. Some of the historical landmarks in the surgical treatment of SUI are needle suspension operations, mid-urethral slings and pubovaginal slings. These are discussed below.
Needle suspension operations
Sub-urethral plication was originally described by Kelly and Dumm in 1913. The first needle suspension method using vaginal needle suspension technique was described by Pereyra in 1959. In 1973, Stamey modified the needle suspension technique by the addition of cystoscopy. Another modification was described by Raz et al. in 1992.
Because of significant recurrence rates at even 1 and 2 years, and the availability of minimally invasive mid-urethral sling procedures, long-needle procedures such as the ‘Pereyra ’, ‘Stamey ’, or ‘Raz ’ procedures, and their other modifications are no longer recommended.
Mid-urethral slings
Surgical treatment of female SUI changed radically when Petros and Ulmsten gave account of integral aspects of urinary incontinence and later provided a concept of midurethral support without tension. This introduced a minimally invasive technique that involved the use of a polypropelene tension-free vaginal tape (TVT) passed retropubically to support the mid-urethra. The success and wide acceptance of this technique in preference to earlier needle suspension procedures is due to various factors: (1) the sling elevates the mid urethra rather than the bladder neck; (2) the sling made of prosthetic material is ‘tension free’ and is not anchored to any tissue giving a dynamic rather than fixed support to the mid urethra; (3) the procedure is minimally invasive and (4), more importantly, it gives good long-term cure rates (84–92%).
The retropubic placement of suburethral TVT was previously associated with a number of perioperative and postoperative complications, including bowel, vascular and bladder injuries. This encouraged urologists to develop a procedure based on similar principles but with minimal morbidity to treat SUI. In 1998, Nickel et al. described a modification of TVT in which a tape was passed through obturator membrane and muscles in female dogs. In 2001, Delorme described a new method of inserting the suburethral tape called the transobturator tape technique. This technique is now as popular as the TVT technique. The main advantage of the transobturator technique is that it avoids the retropubic space and associated complications. It also has a theoretical advantage of less obstruction and postoperative voiding dysfunction.
Pubovaginal slings
Von Giordano is usually credited with carrying out the first pubovaginal sling operation in 1907, using a gracilis muscle graft around the urethra. In 1914, Frangenheim used rectus abdominus muscle and fascia for pubovaginal slings. In 1942, Aldridge corrected urinary incontinence using fascial slings. In 1965, Zoedler and Boeminghous first introduced synthetic slings.
Historical perspective and evolution
The idea of elevating the bladder neck and urethra for the treatment of SUI was known since the beginning of the 20th century. Some of the historical landmarks in the surgical treatment of SUI are needle suspension operations, mid-urethral slings and pubovaginal slings. These are discussed below.
Needle suspension operations
Sub-urethral plication was originally described by Kelly and Dumm in 1913. The first needle suspension method using vaginal needle suspension technique was described by Pereyra in 1959. In 1973, Stamey modified the needle suspension technique by the addition of cystoscopy. Another modification was described by Raz et al. in 1992.
Because of significant recurrence rates at even 1 and 2 years, and the availability of minimally invasive mid-urethral sling procedures, long-needle procedures such as the ‘Pereyra ’, ‘Stamey ’, or ‘Raz ’ procedures, and their other modifications are no longer recommended.
Mid-urethral slings
Surgical treatment of female SUI changed radically when Petros and Ulmsten gave account of integral aspects of urinary incontinence and later provided a concept of midurethral support without tension. This introduced a minimally invasive technique that involved the use of a polypropelene tension-free vaginal tape (TVT) passed retropubically to support the mid-urethra. The success and wide acceptance of this technique in preference to earlier needle suspension procedures is due to various factors: (1) the sling elevates the mid urethra rather than the bladder neck; (2) the sling made of prosthetic material is ‘tension free’ and is not anchored to any tissue giving a dynamic rather than fixed support to the mid urethra; (3) the procedure is minimally invasive and (4), more importantly, it gives good long-term cure rates (84–92%).
The retropubic placement of suburethral TVT was previously associated with a number of perioperative and postoperative complications, including bowel, vascular and bladder injuries. This encouraged urologists to develop a procedure based on similar principles but with minimal morbidity to treat SUI. In 1998, Nickel et al. described a modification of TVT in which a tape was passed through obturator membrane and muscles in female dogs. In 2001, Delorme described a new method of inserting the suburethral tape called the transobturator tape technique. This technique is now as popular as the TVT technique. The main advantage of the transobturator technique is that it avoids the retropubic space and associated complications. It also has a theoretical advantage of less obstruction and postoperative voiding dysfunction.
Pubovaginal slings
Von Giordano is usually credited with carrying out the first pubovaginal sling operation in 1907, using a gracilis muscle graft around the urethra. In 1914, Frangenheim used rectus abdominus muscle and fascia for pubovaginal slings. In 1942, Aldridge corrected urinary incontinence using fascial slings. In 1965, Zoedler and Boeminghous first introduced synthetic slings.
Pathophysiology
Pathophysiology is a complex subject with many interrelated causative factors. Essential anatomic elements responsible for continence include proper mucosal apposition, constant urethral tone, and maintenance of the bladder neck and proximal urethra in the retropubic position. Our understanding of pathophysiology of SUI has changed over the years. As improved diagnostic modalities have provided new insight into the function and dysfunction of the urethral continence mechanism, theories have evolved from being purely anatomic to being both functional and anatomic. In the past, the emphasis was on the change in the posterior urethrovesical angle or the bladder neck, and later the focus shifted to the mid-urethra. Current theories integrate anatomic and functional factors, as well as the effects of neuromuscular injury, aging and hormones. Several hypotheses have been proposed to explain the pathophysiology. These include pressure transmission, Hammock theory, and integral theory.
Enhorning hypothesis
The proximal urethra is an intra-abdominal organ capable of receiving transmitted intra-abdominal pressure. In women with stress incontinence with urethral hypermobility, however, the proximal urethra descends out of the abdomen (note location of the pelvic floor) and cannot receive transmitted abdominal pressure that allows for the urethral sphincteric mechanism to be overpowered, and urine is lost with stress.
Subfascial Hammock concept of urethral support
Subfascial Hammock is a support system that involves the intact pubo-urethral ligaments forming a sub-urethral hammock of support in the mid-urethra. Downward force against this hammock (e.g. when coughing or sneezing) causes urethral compression and prevents bladder neck descent, therefore any leak.
Integral theory
According to Petros and Ulmsten, ‘symptoms of stress, urge,and abnormal emptying mainly derive, for different reasons, from laxity in the vagina or its supporting ligaments, a result of altered connective tissue’. According to the hypothesis, the urethral closure occurs at the mid portion of the urethra and not the bladder neck.
As we currently understand it, two main mechanisms result in SUI: urethral and bladder neck hypermobility and intrinsic sphincteric deficiency. With Urethral and bladder neck hypermobility, weakness of the pelvic floor (ligaments, endopelvic fasciae and muscle) will cause the bladder neck and proximal urethra to descend during elevated intra-abdominal pressure. This hypermobility will prevent compression of the proximal urethra resulting in unequal pressure gradient between the bladder and urethra leading to urinary leak. Injuries sustained during childbirth, aging, hormonal changes at menopause and a few surgical procedures can cause urethral hypermobility.
With intrinsic sphincteric deficiency (ISD), damage to the internal sphincter mechanism or its nerve supply renders the urethral sphincter unable to cope and generate enough resting urethral closing pressure to retain urine in the bladder, resulting in involuntary urine loss during stress. Oestrogen deficiency at menopause leads to atrophy, and replacement of the submucosa of the intrinsic sphincter by fibrous tissue. Previous bladder neck operations, radiation exposure, and neurogenic disease can affect the ability of the sphincter to achieve a perfect seal. There is no consensus on methods objectively identifying ISD. At present, urodynamic leak point pressure and urethral pressure profilometry are used to diagnose ISD. Absence of hypermobility may suggest that the cause of the SUI is ISD.
Most women with SUI, however, have an element of ISD with a variable degree of urethral hypermobility. No standardized tests are available to measure accurately the relative contributions of ISD and hypermobility to the development of SUI.
Surgical options
Before embarking on surgical options for the treatment of SUI, it is prudent to discuss various non-surgical options with the patient (i.e. vaginal support devices and pelvic floor muscle exercises). Pessaries and other mechanical devices modified to selectively support the bladder neck may be effective for treating some cases of SUI, but objective evidence regarding their effectiveness has not been reported. Replacement of the prolapsed anterior vaginal wall with a pessary may unmask incontinence by straightening out the urethrovesical kinking that may have been responsible for either continence or some degree of urinary retention. Pelvic floor training also seems to be an effective treatment for women with stress and mixed incontinence. It is better than no treatment or placebo. Pelvic muscle exercise seems to be superior to electrical stimulation and vaginal cones in the treatment of stress incontinence. These non-surgical options have low cure rates and are dependent on patient compliance. Numerous surgical methods have been described. The categories are presented in Table 1 .
| Open abdominal retropubic suspension (e.g. Burch colposuspension, Marshall–Marchetti–Krantz procedure) |
| Laparoscopic retropubic suspension |
| Needle suspensions (e.g. Pereyra and Stamey procedures) |
| Vaginal anterior repair (anterior colporrhaphy with Kelly plication) |
| Suburethral slings (including traditional midurethral slings and pubo-vaginal slings) |
| Vaginal paravaginal repair |
| Peri-urethral injections |
| Artificial sphincters |
Anti-incontinence surgical procedures do not necessarily work by restoring the same mechanism of continence that was present before the onset of incontinence. They are likely to work through an alternative compensatory approach, creating a new mechanism of continence. The midurethral sling provides continence by creating functional kinking of the midurethra during increased intra-abdominal pressure and the associated rotational descent of the bladder neck and proximal urethra.
Contraindications
A clear contraindication to mid-urethral sling or pubovaginal sling surgery is pure urge incontinence or mixed urinary incontinence, in which urge is the predominant component. An inherent risk of any sling procedure is de-novo or worsening urge symptoms; thus, surgeons must identify and treat the presence of an urge component before surgery. Poor detrusor function is a relative contraindication to sling surgery because the potential for urinary retention is increased. Women with absent or poor detrusor function in the presence of SUI are at higher risk of experiencing prolonged postoperative urinary retention.
Anterior colporrhaphy and Kelly suburethral plication
Anterior colporrhaphy and Kelly’s sub-urethral plication or its modification (TeLinde’s) have no place in surgical treatment of SUI. In many low-resource countries, however, where patients cannot afford the expensive tapes, suburethral plication still has a place in the management of mild SUI.
Tension-free vaginal tape
Tension-free vaginal tape is based on integral theory set forth by Petros and Ulmsten, and is based on the following principles: (1) it is a mid urethral rather than bladder neck suspension; (2) it is a knitted polypropelene mesh (45 cm × 1.1 cm × 0.7 mm) sling: (3) it is not sutured or anchored to any structure (pubic bones, ligaments or rectus sheath); (4) it is therefore considered tension free (reduces incidence of voiding difficulties); and (5), compared with conventional anchored slings, the newer tension-free sling devices are not anchored but instead suspended through the retropubic space (hence the name). At first, the sling is held in place by friction (velcro effect) from the opposing tissues. Over time, collagen formation fixes the mesh more strongly within the suburethral and paravaginal tissues. There are two approaches to TVT, the ‘bottom-up’ vaginal approach and the ‘top-down’ abdominal approach. The vaginal approach is discussed below.
Before surgery
Before surgery, aspirin and other anticoagulants are discontinued for an adequate period. Urinalysis and urine culture must rule out urinary tract infection.
Tension-free vaginal tape device
The TVT Device (Johnson & Johnson, Gynecare Division) is a polypropylene mesh tape that is covered with a plastic sheath and attached to two stainless steel introducer needles. The device, when used in conjunction with the TVT Introducer and TVT Rigid Catheter Guide, make up the TVT System. The catheter guide fits a standard 18 Fr Foley catheter.
Technique
Local anaesthetic is injected into the skin just above the pubic tubercle on both sides of the midline; it is continued into the space of Retzius. The anterior vaginal wall is infiltrated with dilute (1: 200,000) adrenaline in saline. A small vertical incision is made on the anterior vaginal wall at the mid urethra. The vaginal wall tissue is dissected off the urethra to expose the mid urethra, and continued further paraurethrally toward the endopelvic fascia. The rigid guide, passed into the bladder through the urethra, allows mobilization of the bladder neck and urethra away from the path of the TVT device. An assistant pivots the handle of the guide to one side (towards he patient’s thigh) to expose the patient’s endopelvic fascia on the opposite side. The endopelvic fascia is punctured with the TVT needle, and advanced through the space of Retzius and to the anterior abdominal wall. The needle must hug the posterior wall of pubic symphysis during this manoeuver. The tented skin over the needle is incised so as to allow the needle to emerge. The bladder is filled with 250 ml saline. A cystoscopy is carried out with the needle in situ to rule out bladder and urethral injury. The bladder is emptied. The needle is advanced to bring the tape above the abdominal wall. The same procedure is repeated on the contralateral side. The tape at both abdominal ends is cut and the needles are removed. The tape should be pulled upward on both sides until only a few drops leak out when the patient coughs: tension test. The tension test requires patient participation. Therefore, it is recommended that the TVT procedure be carried out under local anaesthesia with intravenous sedation or regional anaesthesia. General anaesthesia can be used by surgeons experienced with the TVT technique. The only measurement here of tension will be spacing with a blunt instrument (such as number 8 Hegar dilator, hemostat or Mayo scissors), which is inserted between tape and urethra. The key to success is that the sling should be ‘just right’ and not ‘too snug’ or ‘too loose’. Do not place the tape like a ‘string of Bow’.
After surgery
Residual urine is measured to rule out retention. Prophylactic antibiotics are prescribed according to local practice. After surgery the patient is instructed to restrict their normal activity for 1 or 2 weeks depending on job content. The patient is recommended to refrain from heavy exercise (i.e. cycling, jogging and lifting) for at least 3–4 weeks and to refrain from intercourse for 1 month. Postoperative catheterization is not generally needed. TVT can be carried out as day surgery. Patients must be observed for retropubic haematoma before discharge. After an initial follow-up at 3 weeks, patients are seen at 6 months and then annually for 3–5 years.
Results
Most studies report an 85% cure rate with an additional 5–10% significantly improved. Cure rates of 85% as a primary procedure and 75% as secondary procedure have been reported. A recent exhaustive meta-analysis comparing tension free vaginal tape to Burch colposusppension showed that tension free vaginal tape outperformed the Burch colposuspension. A recent study with the longest period of follow up reported for TVT has shown a subjective and objective cure in 81% of patients at a mean follow up of 7.6 years, with a further 16% showing improvements in their symptoms.
The TVT procedure is akin to the conventional sling operation in that a supportive hammock of prolene mesh is placed below and around the urethra. It differs from the pubovaginal sling procedure because the prolene mesh is placed distal on the urethra, away from the bladder neck. In this location, the mesh does not interfere with the funnelling of the bladder neck that proceeds normal voiding, and voiding problems are not a common result.
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