2 The procedure
2.1.1 Anal fistula is an abnormal tract between the anal canal and the skin around the anus. Fistulae usually result from perianal abscesses and can be associated with conditions such as Crohn's disease. Intersphincteric fistulae are the most common type and cross only the internal sphincter. Trans-sphincteric fistulae pass through both the internal and external sphincters. Fistulae may be complex, with several openings onto the perianal skin.
2.1.2 Symptoms include pain or discomfort in the anal area, and discharge of blood or pus.
2.1.3 Treatment usually involves surgery and depends on the position of the fistula in relation to the sphincters. Intersphincteric fistulae are usually laid open. The laying open of trans-sphincteric fistulae involves muscle division that may impair continence (usually to a minor degree). A seton may be used to effect a slow, controlled division of the sphincter below the fistula tract. An alternative is to use an advancement flap, but early success may not be continued in the longer term.
2.1.4 Less invasive techniques, developed with the aim of minimising the risk of incontinence, include injection of fibrin glue.
2.2.1 Closure of anal fistula using a suturable bioprosthetic plug aims to leave the sphincter muscles intact, allowing the use of subsequent treatments if required.
2.2.2 The procedure is usually carried out with the patient under general anaesthesia. The fistula tract is identified using a probe or by imaging techniques, and may be irrigated. A conical plug, usually made of porcine intestinal submucosa, is pulled into the tract until it blocks the internal opening, and is sutured in place at the internal opening. The external opening is not completely sealed so that drainage of the fistula can continue. The plug acts as a scaffold into which new tissue can grow.
2.2.3 More than one device is available for this procedure.
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview.
2.3.1 A randomised controlled trial (RCT) of 90 patients treated by a suturable bioprosthetic plug or endorectal advancement flap reported successful fistula closure in 82% (37/45) and 64% (29/45) of patients respectively at 6-month follow-up (p < 0.05).
2.3.2 A non-randomised comparative study of 232 patients treated by a suturable bioprosthetic plug, fibrin glue, draining seton or advancement flap reported healing rates of 59% (16/27), 39% (9/23), 33% (28/86) and 60% (58/96) respectively at 12-week follow-up (p < 0.05 between the groups). A non-randomised comparative study of 245 patients treated by a suturable bioprosthetic plug, fistulotomy, staged fistulotomy, draining seton, cutting seton, fibrin glue or advancement flap reported healing rates of 32% (14/43), 87% (104/120), 50% (18/36), 5% (1/21), 69% (9/13), 80% (4/5) and 75% (3/4) of patients respectively at 3-month follow-up (p < 0.001 for plug versus fistulotomy).
2.3.3 The RCT of 90 patients reported significantly higher quality of life scores (Fecal Incontinence Quality of Life Scale; higher scores best) in patients treated by a suturable bioprosthetic plug compared with those treated by endorectal advancement flap at 6-month follow-up (85.9 versus 65.3, p < 0.001).
2.3.4 The Specialist Advisers stated that the key efficacy outcome is healing (clinically and on magnetic resonance imaging [MRI]).
2.4.1 In a non-randomised comparative study of 80 patients treated by a suturable bioprosthetic plug or endorectal advancement flap, 14% (5/37) of patients in the plug group were treated with antibiotics postoperatively because of pain and increased drainage.
2.4.2 The Specialist Advisers listed reported adverse events as new abscess formation and plug extrusion.
2.5.1 The Committee noted that anal fistulae can cause distress to patients and are difficult to treat successfully. The Committee recognised the potential usefulness of suturable bioprosthetic plugs if further evidence supports their efficacy in a substantial proportion of patients.
2.5.2 The Committee was advised of the potential value of MRI in the diagnosis of complex fistulae and in assessing the results of treatment.