John: Hello, I'm John Hilton, editor in the Cochrane Editorial and Methods department.  Urinary incontinence is a distressing condition for which there are a variety of treatment options. June Cody from the Cochrane Incontinence Group and colleagues have investigated the effects of a particular type of surgery. They updated the review's findings on the effects of the operations in 2015, and published an extension in July 2017, to include more on the economic aspects. Here's June to tell us about the evidence on the clinical effects.

June: When someone suffers from stress urinary incontinence, exertion, coughing, sneezing or laughing can cause an involuntary leakage of urine. It’s the commonest form of incontinence in women, affecting one in three over the age of 18 years at some point in their lifetime, reducing quality of life and causing problems with sexual intercourse. It can also mean that the woman needs to spend a significant amount of money managing the symptoms.
Over the years, surgery to stop stress urinary incontinence has become less invasive and we looked at one of the various types available, namely the mid-urethral sling operation. In this operation, a tape is placed underneath the urethra, which is the tube that carries urine out of the bladder. When the woman coughs, the tape compresses the tube, thus providing the support necessary to prevent urine leakage.
There are two main ways of carrying out mid-urethral sling operations, either by inserting a tape behind the pubic bone through the abdomen ('retropubic'), or through the groin ('transobturator').
We looked at the effects and costs for both methods and also compared different ways of inserting the tape, and using tapes made from different materials. 
In total, we amassed 81 separate pieces of research. More than 12,000 women had agreed to take part in these studies and they showed that over 80% of women with stress urinary incontinence are cured, or have significant improvement in their symptoms, with either operation, for up to five years after surgery. This is irrespective of which tape is used and the route of tape insertion. The information available for quality of life shows that this improves as a result of these operations, with no clear difference between the two procedures.
In regard to adverse effects, there is moderate quality evidence that tape-related complications are low. Tapes passing behind the pubic bone seem to carry a greater risk of injuring the bladder during the operation and of women experiencing problems emptying their bladder completely after surgery. On the other hand, this operation leads to less groin pain in the short term and there is some limited evidence that this way of inserting the tape has a lower risk of requiring a repeat operation in the long term compared to tapes passing through the groin.
Most of our results are based on moderate quality evidence. Most trials did not describe their methods clearly, thus leading to some degree of uncertainty in the findings. At present there are only a limited number of randomised controlled trials that have published data beyond five years after surgery. This means that evidence about how effective and safe these procedures are in the longer term lags behind the evidence for them in the short and medium term (up to five years). Longer-term data are required. This would substantially increase the evidence base and provide clarification regarding uncertainties about long-term effectiveness and adverse event profile.

John: If you’d like to look in more detail at the current evidence, June’s review can be found at Cochrane library dot com with a simple search for 'mid-urethral sling for incontinence'.