2 The procedure

2.1 Indications

2.1.1 Stress urinary incontinence is the involuntary leakage of urine during exercise or movements such as coughing, sneezing and laughing. It is usually caused by weak or damaged muscles and connective tissues of the pelvic floor, or by weakness of the urethral sphincter itself. It is estimated that 10–52% of adult women have some form of stress incontinence.

2.1.2 Typically, first-line treatment is conservative and includes lifestyle changes such as weight loss, pelvic floor muscle training, electrical stimulation and biofeedback. If the condition does not improve, surgical alternatives in women may include colposuspension, the use of tension-free vaginal tape, transobturator foramen procedures or traditional suburethral slings.

2.2 Outline of the procedure

2.2.1 Biological slings may be made from the patient's own fascial tissue (autograft), from human donor tissue (allograft) or from animal tissue (xenograft). Allografts are solvent dehydrated or freeze dried, and may be gamma irradiated. Autologous fascial slings are the most established option.

2.2.2 Suburethral sling procedures involve making an incision in the lower abdomen and one in the anterior vaginal wall. An instrument is tunnelled between the incisions to introduce the sling and position it around the bladder neck where it forms a supportive hammock. There are three main methods of positioning the sling, depending on its length. A full-length sling passes through the retropubic space, underneath the urethra to the other side, and is fixed by sutures to the anterior abdominal wall. Shorter slings are attached by suspending sutures at each end of the sling to the anterior abdominal wall. Alternatively, bone screws may be used to secure the sutures into the pubic bones. Once the sling is in position, a cystoscopy may be performed to check that there has been no bladder perforation.

2.3 Efficacy

2.3.1 Two non-randomised controlled trials compared allograft slings with autograft slings. These reported similar improved rates of continence: 71% (45/63) and 74% (77/104) for the allograft groups; and 77% (55/71) and 73% (22/30) for the autograft groups. One of these studies reported that 89% (93/104) of women with allograft slings and 90% (27/30) of women with autograft slings were satisfied and would undergo the procedure again. In another study comparing long-term outcomes, subjective stress continence was reported by 92% (24/26) of patients with allograft slings at 42 months, and 91% (19/21) of patients with autograph slings at 35 months. A case series of 198 women with autograft slings reported an overall success rate of 72% (142/197) after a median follow-up of 6 years. Another case series reported that 85% (75/88) of patients who were followed up for longer than 5 years were continent.

2.3.2 One randomised controlled trial reported that 82% (56/68) of women had improved rate of continence with a xenograft sling, compared with 88% (53/60) of women who had had a vaginal tape procedure (not statistically significant). The patient satisfaction rates were similar for the two groups. In a second randomised study of 139 patients, published in abstract form, 12.5% patients (6/48) with a xenograft sling required reoperation within 12 months for delayed failure. There were no reports of failure in the vaginal tape or autograft group at 12 months. For more details, refer to the Sources of evidence.

2.3.3 The Specialist Advisors stated that there are concerns about the long-term efficacy of this procedure.

2.4 Safety

2.4.1 The two most commonly reported complications were urge incontinence and urinary retention. Urge incontinence affected between 3% (5/152) and 50% (5/10) of women. One study reported that 94% (232/247) of women had transient urinary retention (for longer than 1 day postoperatively; mean duration of catheterisation was 8.4 days), and prolonged urinary retention was reported in 2% (1/63) to 10% (3/30) of women. Two studies reported severe or persistent pain in 1% (1/74) and 4% (5/134) of women, respectively. Other complications included infection, pelvic haematoma, haemorrhage and urethral stenosis.

2.4.2 The Specialist Advisors noted that potential adverse effects include urethral obstruction and retention, bladder perforation, haemorrhage, infection and urgency. There is also an additional potential risk of infection associated with the use of cadaveric tissue.

2.5 Other comments

2.5.1 It was noted that a variety of types of biological slings are available, including allogenic, xenogenic or autogenic grafts; and that outcomes may vary according to the type of graft used. It was also noted that a variety of methods are used for the implantation of slings.

2.5.2 It was noted that this procedure is different from the tension-free vaginal tape insertion procedure (which is subject to NICE guidance – see Further information).