2 The procedure
2.1.1 Faecal incontinence occurs when a person loses the ability to control their bowel movements and is unable to retain faeces in the rectum. It can be caused by a wide variety of conditions that affect either the anatomy or function of the anal sphincter. Perineal injury during childbirth is a common cause of faecal incontinence in women. Faecal incontinence can also be caused by neurological disorders such as spinal injury and multiple sclerosis, or it can result from anorectal surgery. Faecal incontinence is associated with considerable physical and social disability.
2.1.2 First-line treatment for faecal incontinence is usually conservative and includes antidiarrhoeal medication and pelvic floor muscle training. In patients for whom conservative treatments prove inadequate, alternatives include surgery to tighten the anal sphincter (overlapping sphincteroplasty), sacral nerve stimulation, creation of a new sphincter from other suitable muscles (for example, dynamic graciloplasty), implantation of an artificial sphincter or the creation of a permanent colostomy.
2.2.1 Bulking agents are injected into the wall of the lower rectum in order to create one or more bulges, narrowing the opening through which stool will pass and thereby helping to retain it within the rectum. The procedure is usually performed under local anaesthesia. Several millilitres of bulking agent are injected into the submucosa just above the dentate line. Injections can be done via the anal canal or via a trans-sphincteric route, with or without ultrasound guidance. More than one injection may be given.
2.2.2 Several bulking agents are currently used, including collagen, silicone particles and carbon beads.
2.3.1 In the largest case series, 82 patients had significant improvements in continence scores compared with baseline at 6 months (p < 0.001), which was maintained at 12 months in a subset of 42 patients. Similar results were reported in a case series of 18 patients, who had a significant improvement in continence grading compared with baseline at 12 months (p = 0.0002). The authors noted that the improvement in continence score was significantly higher in patients who received injections at two or more sites. In another case series, 60% (6/10) of patients reported improvement from baseline at 6 weeks after the procedure, although only 30% (3/10) still reported some improvement at 6 months.
2.3.2 Two studies reported on quality of life and patient satisfaction after the procedure. In the case series of 18 patients, improvement compared with baseline was reported in patient satisfaction (p = 0.053) and in all quality-of-life scales (p = 0.006–0.059) at 12 months. In the second study of 82 patients, all quality-of-life domains, measured using a faecal incontinence scale, had improved compared with baseline at a median follow-up of 6 months. For more details, refer to the 'Sources of evidence' section.
2.3.3 The Specialist Advisers commented that there is a lack of good-quality data on the efficacy of this procedure. In particular, they noted that there is uncertainty about the duration of any possible benefits and whether repeat injections are needed to maintain this effect.
2.4.1 Few complications were reported in the studies. The most commonly reported complication was pain at the injection sites. In the largest case series, 7% (6/82) of patients reported some pain following the procedure. In a smaller case series, half of the patients (5/10) experienced pain or minor ulceration at the injection site or in the anal canal for up to 10 weeks after the procedure. Other complications included leakage of the bulking agent in 1 of 10 patients and, in a different study, passing of the bulking agent in 2 of 18 patients. For more details, refer to the 'Sources of evidence' section.
2.4.2 The Specialist Advisers listed infection, pain and leakage of the bulking agent along the injection track as the main complications of the procedure. Migration of the bulking agent, and rectovaginal fistula were also noted as possible complications.