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What is the role of mid-urethral slings in the management of stress incontinence in women?

Cathryn MA Glazener
Editorial Article

Urinary incontinence is very common in women: about 40% have persistent urinary incontinence after childbirth.[1] Urine leakage can affect quality of life, including social activities, work, psychological wellbeing, and sexual relationships. Women with stress urinary incontinence (leakage when they cough, laugh, or exercise) normally try pelvic floor exercises in the first instance. If this fails, more women than ever before are seeking a surgical cure.

The most common surgery to treat this problem in developed countries is the mid-urethral sling, or tape, made of non-absorbable polypropylene mesh. Between 2005 and 2013 more than 3.6 million slings were used to treat women with stress urinary incontinence.[2]

The introduction of these slings about 20 years ago has led to a revolution in the surgical treatment of women with stress urinary incontinence, at least in developed countries, where older operations have all but been abandoned.[3] These include anterior repair (less effective), colposuspension (a more major operation with more adverse effects) and traditional slings (more difficult to insert; more invasive).[4-6]

In England, for example, during 2013-14 about 12,000 women had a mid-urethral sling operation and 500 had another type of continence procedure (colposuspension or traditional sling).[7] In contrast, 10 years earlier, about 7000 had a mid-urethral sling and 1650 had a colposuspension or traditional sling. Thus, most women now have a mid-urethral sling, and, because of its perceived safety and efficacy, there has been a substantial increase in the total number of women having continence surgery.

The slings are normally made of non-absorbable plastic polypropylene mesh. They are placed under the urethra and pull up when the woman coughs or laughs, so obstructing the urethra just when leakage might occur, but tension-free when at rest. There are two main methods of insertion of slings: retropubic (bottom-to-top behind the pubic bone) and transobturator (side-to-side through the obturator space). A newly updated Cochrane Review compares these two approaches as well as different ways of performing each operation and the use of different sling materials.[8]

The review found that the slings are effective in curing incontinence, at least in the short and medium term, with about 80% of women becoming dry and 70% remaining so five years later. There was very little to choose between the retropubic and transobturator routes in terms of curing incontinence, but the adverse effects were different. Women who had a retropubic sling were more likely to have bladder perforation at the time of surgery. However, if bladder perforation is recognised at the time, and the trochar (insertion tool) withdrawn, there are few long-term problems. Transobturator slings, on the other hand, are more likely to be associated with pain in the groin or leg; based on evidence from the randomised controlled trials, this generally resolves within 6 to 12 months. Women were less likely to develop difficulty voiding with the transobturator slings, but they were also more likely to need repeat surgery because of recurrent incontinence. Overall, however, few side effects were reported in the trials at one year and up to five years.

A major shortcoming of the trials is that very few of them reported outcomes beyond the first year. In fact, 35 of the 84 trials included in the review were conducted sufficiently long ago to have provided information about long-term leakage and, crucially, adverse effects at 5 years, but only four actually did so.

Safety concerns about slings have made international headlines in recent months. independent reviews of the evidence for efficacy, effectiveness and safety have already been conducted or commissioned in Australia, Denmark, the European Commission, France, the Netherlands, New Zealand, the UK, and the USA. The recent UK Medicines and Healthcare Products Regulatory Agency (MHRA) report concluded: “Women have reported serious and debilitating problems following surgical treatment for stress urinary incontinence…using vaginal mesh implants. Although the number of reports to MHRA is low compared to the overall use of these implants, there is some evidence of under-reporting and there are concerns that MHRA is not aware of all women who have experienced problems.”[2] The report goes on to conclude that “the overall benefit outweighs the relatively low rate of complications”.

The preliminary opinion on surgical meshes from the European Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) review broadly concurs with this view.[9] An earlier review of the evidence, the York report, also found the rate of adverse effects to be low.[10] There is also extensive information on the different tapes available and surgical techniques involved in the recently updated NICE guideline on the management of urinary incontinence in women.[11]

In the meantime, surgeons continue to use mid-urethral slings, albeit with enhanced advice about the issues women need to consider. A booklet commissioned by the Scottish Government which gives detailed information about the synthetic mid-urethral sling procedure is available.[12] It is intended to provide informed choice and information for women contemplating sling surgery and their surgeons to use in counselling and decision making.

The debate about slings is all about how often women suffer long-term problems set against undoubted benefits in curing incontinence. Although this updated Cochrane Review compares the two most common operations in current practice in developed countries, we need more evidence about how well they compare with the older types of surgery that they have superseded[4,5] and any newer operations, such as mini-slings[13]. If surgeons are to re-learn how to perform the older operations, it would be helpful to look first at indirect comparisons, as the direct evidence is not sufficient.

Conservative alternatives to surgery include no treatment, containment with absorbent pads, weight loss, intravaginal mechanical devices, pelvic floor muscle training with or without biofeedback, cones, electrical stimulation, and (for postmenopausal women) local oestrogens. The essential message is that women with urinary incontinence must be aware of all the options available to them including their chance of success and risk of adverse effects, and explore conservative options first, before considering invasive surgery.

Related Cochrane Reviews