Considerable debate exists concerning the thickness and consistency of the advancement flap repair. Most authors [5, 22, 31–37] have used a flap consisting of mucosa, submucosa, and some of the most superficial fibers of the internal anal sphincter. This technique allows for a relatively bloodless dissection and yields a substantial flap with enough elasticity to be advanced over the internal opening. However, advancement flaps consisting of only mucosa and submucosa also have been described [38], as have full-thickness flaps consisting of the full thickness of the rectal wall [4, 39–41]. Some studies have been performed comparing the use of full-thickness flaps with flaps consisting of only mucosa and submucosa [40–42]. A small, retrospective study suggested improved healing after the use of full-thickness flaps without additional impairment of continence [40]. Another recent small, randomized study by Khafagy et al. [41] also showed better results for patients in whom a full-thickness flap was created; however, this group found a higher incidence of impaired continence in these patients. Roig et al. [42] performed a meticulous retrospective analysis of 70 patients undergoing endorectal flap repair and found no differences in healing, although they did report a trend toward poorer functional results after the use of full-thickness flaps. Even though there is a small amount of evidence, it would seem prudent to add some superficial sphincter fibers to the advancement flap to strengthen the flap coverage. It is noteworthy that most large series that have been published and have used this technique have utilized this partial-thickness flap incorporating the superficial sphincter.

Several factors that might affect the outcome of transanal advancement flap repair have been analyzed. Several authors found a detrimental effect of the use of tobacco [43, 44]; however, this effect could not be confirmed by others [4, 37]. In a previous study designed to assess rectal mucosal blood flow before and after flap repair in smoking and nonsmoking patients, Zimmerman et al. [32] observed a significant decrease in rectal mucosal blood flow after creation of the flap. Furthermore, rectal mucosal blood flow was found to be significantly lower in smoking patients both before and after transanal advancement flap repair; however, no correlation was found between blood flow and the outcome of transanal advancement flap repair [45]. This observation indicates that diminished rectal mucosal blood flow does not have a detrimental effect on transanal advancement flap repair. However, several investigators found a decreased healing rate after advancement flap repair in patients who smoke cigarettes, and it would seem sensible to counsel patients about this finding. Smoking cessation seems prudent in patients with recurring fistulae for whom repair will be attempted with an advancement flap. Ellis and Clark [44] found a negative effect of smoking on the outcome of mucosal advancement but not on the outcome of anocutaneous advancement flap repairs; therefore, this type of repair possibly can also be considered in such cases.

Some authors advocate preoperative seton drainage because it allows drainage of the fistulous tract, thereby reducing inflammatory activity, reducing the chance of interim abscess formation, and resolving secondary tracts [2, 46, 47]. Although several authors [2, 22, 46, 47] found that preoperative seton drainage improves healing after transanal advancement flap repair, this beneficial effect could not be confirmed by others [43, 48, 49]. Moreover, the reported series were rather small and study populations often were heterogenous, including patients with rectovaginal fistulae and those with fistulae caused by Crohn’s disease. In conclusion, there seems to be no convincing evidence for the use of seton drainage before transanal advancement flap repair even though it has been reported to be a specific part of surgical algorithms for staged repair [50, 51]. However, it is possible that seton drainage was used in more difficult cases and that the preoperative eradication of active sepsis may have allowed the rate of healing of complex fistulae to approach that of more straightforward cases. Moreover, we acknowledge the importance of eradicating all active perianal sepsis before attempting any repair of a complex perianal fistula. For this purpose, a seton drain can be a useful tool, and preoperative seton drainage is still an important part of the surgical armamentarium in surgery for perianal fistulae, as opposed to the use of a seton for definitive cutting purposes, which may be associated with a significant and under-recognized incidence of functional continence disturbance [52, 53].

Lindsey and colleagues [49] have reported that the efficacy of a repeat transanal advancement flap repair is limited because the scarring associated with a failed advancement flap compromises the changes of success with subsequent flaps. However, this statement is not supported by the literature. In a study conducted by Kodner et al. [5], nine patients, in whom the initial flap repair failed, underwent a second operation, which was successful in all patients. In a further study conducted by Mizrahi and colleagues [4], 12 patients underwent repeat surgery because of initial flap failure, 8 of whom (67%) healed. Several large series [4, 22, 38, 43, 54] have investigated the use of transanal advancement flap repair for recurrent fistulae. Our group [43, 54] found that prior operations did not influence the healing rate of this technique. We believe this is a strong argument in favor of utilizing this technique where possible in patients with recurring complex fistulae.

Recently, several large series [4, 22, 38, 43, 54] have investigated the use of transanal advancement flap repair for recurrent fistulae; unfortunately, the impact on fecal continence was not properly assessed in any of these studies. It has been suggested that transanal advancement flap repair may result in impaired fecal continence. The reported incidence of this side effect varies between 8 and 35 % [31, 38]. Any decrease in fecal continence is usually minor (soiling or incontinence for flatus); according to some authors, inclusion of internal anal sphincter fibers contributes to the impairment of continence. On the basis of this assumption, it might be possible that a second flap repair results in further deterioration of fecal incontinence. A recent study of 87 patients by Mitalas et al. [54] showed that a repeat transanal advancement flap repair has a healing rate comparable to the first attempt without significant deterioration in postoperative fecal continence.

The use of mucosal advancement flap repair of perianal fistulae in patients with Crohn’s disease has been investigated by several authors. Initially, reticence with using this technique was advocated because reported healing rates varied widely, between 33 and 83 % [39, 55]. Furthermore, only small groups of patients were reported. Makowiec et al. [56] reported a relatively large series consisting of 36 operations in 32 patients with Crohn’s disease who were undergoing mucosal advancement flap repair. Even though short-term success seems to be acceptable (only four immediate failures were reported), fistula recurrence was reported in 17 patients, bringing the cumulative probability of overall fistula recurrence to 66 %. Functional results were, however, reported to be good. These results are remarkably similar to those of Mizrahi et al. [4] and Sonoda et al. [22], who reported healing rates of 43 and 50 %, respectively. Unfortunately, neither of these author groups presented a detailed objective analysis of the functional results. It is noteworthy that both groups found that the presence of Crohn’s disease was a significant negative predictor of success.

A recent systematic review on this subject by Soltani and Kaiser [57] computed the weighted average healing rate of mucosal advancement flap repair of perianal fistulae in patients with Crohn’s disease to be around 64 %. Unfortunately, they based their calculation of the weighted average healing rate on only immediate healing rates. Two relatively large studies [58, 59] that were included in this calculation reported healing rates of 75 and 71 %, respectively. In these studies, further recurrences were reported, bringing the ultimate success rates down to 44 and 50 %, respectively. Furthermore, small series (fewer than ten patients) seem to be over-represented in this calculation.

In conclusion, the healing rate of mucosal advancement flap repair of perianal fistulae in patients with Crohn’s disease is low. However, healing is possible and functional results seem to be relatively good, although few detailed data are available. Therefore, this procedure can be considered in selected patients who are willing to accept a relatively low chance of a successful outcome.

An under-utilized technique that was originally described by the group at St. Mark’s Hospital in London in 1993 [58] and later modified by Athanasiadis et al. [60] is fistulectomy with immediate sphincter repair. Some promising results with this technique have been published, although it is likely that the technical challenge in performing this technique correctly is the reason that it has not found widespread acceptance.

Anocutaneous advancement flaps were introduced in the treatment of complex perianal fistulae by del Pino et al. [66]. They reported a small number of patients with promising results. According to these authors, this procedure does not result in anatomic alteration of the anal canal, so all other operative choices are subsequently still feasible. Others have reported similar results; however, the technique has not found widespread acceptance.

In recent years, the Surgisis anal fistula plug (Cook Surgical Inc., Bloomington, IN) has been developed as an alternative to traditional fistula surgery. This plug consists of an extracellular matrix derived from the submucosa of porcine small intestine. This matrix supports remodeling of the host tissue, resulting in closure of the fistulous tract, and it does not encapsulate when implanted. According to some authors, this minimally invasive technique provides a simple and safe option in the treatment of fistulae. Initially, the reported healing rates were high – up to 87 % [74, 75]. More recently, however, less ­promising results have been reported, with healing rates ­dropping to 41 % [76], 24 % [77], and 14 % [78] in more complex fistulae.

A relative newcomer is the LIFT procedure (Fig. 36.3a–e), which recently was described by Rojanasakul et al. [62], although aspects of this approach had been reported previously [60, 64]. Relatively few data are available on this technique; however, the results seem to be promising.