Description

A prevalent and complex fistula type is the high transsphincteric (TS) fistula. It typically runs through the upper two-thirds of the external anal sphincter (EAS) and is, due to the high risk of fecal incontinence, not suitable for fistulotomy and sphincter sparing treatment is required. To be included in this trial the participants should have a single, continuous TS fistula of cryptoglandular origin, that is treated by loose seton drainage for at least 2 months and is mapped by MRI. Participants with IBD, hidradenitis suppurativa or a malignant fistula will be excluded. Intervention Fistula Laser Closing (FiLaCTM) (Biolitec, Germany) is an endofistular technique, using a radial-emitting laser fiber that emits laser light with a maximum penetration depth of 2 - 3 mm. It destroys both the crypt gland and the additional epithelial layer of the fistula without damaging the sphincter. The fiber is inserted until the internal opening, activated and pulled backwards slowly, allowing the laser to have its effect. The external opening is excised and the internal opening is closed with a single absorbable suture. Rectal advancement flap is currently the gold standard for sphincter sparing treatment of high transsphincteric fistulae. The fistula is cored out and an advancement flap is made of mucosa and submucosa. The opening of the fistula in the flap is excised, the residual internal opening is closed with absorbable suture and the flap is sutured below the fistula to the anoderm. The advancement flap is a difficult technique that requires a relatively large transanal dissection that results in postoperative pain and may lead to disturbances in continence. Preliminary results with the Filac technique show fistula healing rates comparable to the advancement flap. Due to its simplicity, speed and minimal invasiveness the investigators expect a benefit for the participants in terms of postoperative pain, operating time and quality of life.