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 Table of Contents  
Year : 2018  |  Volume : 7  |  Issue : 1  |  Page : 12-15

Mucosal advancement flap for fistula-in-ano: A single-institution experience

Department of Colorectal Surgery, St. Vincent's Hospital Melbourne, Melbourne, Victoria, Australia

Date of Web Publication30-Aug-2018

Correspondence Address:
Yui Kaneko
Department of Colorectal Surgery, St. Vincent's Hospital Melbourne, Melbourne, Victoria
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1941-8213.240254

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Background and Objective: Mucosal advancement flap (MAF) is a well-described definitive treatment for complex fistula-in-ano, with high healing rates ranging from 37 to 87% for cryptoglandular fistula, but with mild incontinence rates of up to 35%. There is a paucity of Australian data to support the efficacy and complication rates of MAF, nor predictive factors for success. Patients and Methods: This was a retrospective study, with ethical approval granted by St. Vincent's Hospital Melbourne (SVHM) Quality and Risk Unit. Patients who underwent MAF at SVHM and St Vincent's Private Hospital Fitzroy from 2011 to 2015 were included in the study; all data were collected from patient medical records. Results: A total of 65 patients were treated with MAF during the study period. Fistula etiology was cryptoglandular in 82%, anovaginal in 11%, and perianal Crohn's disease in 7% of patients. Overall success rates for MAF were 66% for cryptoglandular fistula, 14% for anovaginal fistula, and 40% for Crohn's fistula. Excluding anovaginal fistulae, the success rate of MAF was 74% for males and 57% for females. MAF performed for an anterior internal opening was associated with a success rate of 65% versus 56% for a posterior internal opening. Postoperative fecal incontinence rate was 6%. Five of the patients with failed MAF underwent a second sphincter-preserving procedure; none of these were successful. Conclusion: This study supports the use of MAF for the treatment of complex fistula-in-ano, with a success rate compatible with existing literature and a low incontinence rate.

Keywords: Complex anal fistula, fistula-in-ano, mucosal advancement flap

How to cite this article:
Kaneko Y, Lam D, Keck J, Woods R. Mucosal advancement flap for fistula-in-ano: A single-institution experience. World J Colorectal Surg 2018;7:12-5

How to cite this URL:
Kaneko Y, Lam D, Keck J, Woods R. Mucosal advancement flap for fistula-in-ano: A single-institution experience. World J Colorectal Surg [serial online] 2018 [cited 2021 Aug 2];7:12-5. Available from: https://www.wjcs.us.com/text.asp?2018/7/1/12/240254

  Introduction Top

Anal fistula is a common condition in the population associated with significant patient morbidity. Mucosal advancement flap (MAF) has been a well-described definitive treatment for complex fistula-in-ano; however, the management of this condition can be complicated and technically challenging. The aim of MAF is to achieve healing of the fistula while preserving anal continence, although concerns remain regarding the variable outcomes of this procedure, especially in their long-term outcome and postoperative fecal continence.

Previous studies have shown variable healing rates ranging from 37% to 83%[1],[2],[3],[4],[5],[6],[7] with mild fecal incontinence rates of up to 35%.[1] Difference in outcome among studies may reflect differences in the pathogenesis of the fistulas themselves where Crohn's disease and anovaginal fistulas were reported to have low success rates compared to cryptoglandular fistulas.[1],[4],[5],[6] Variation in surgical techniques between institution and surgeons, length of follow-up period and previous fistula surgery may also impact on the outcome.

There have been extensive studies on MAF; however, the Australian data for MAF are still limited. Thus, the aim of this study is to evaluate the efficacy of the technique with respect to healing and complication rates, especially on the impact on fecal continence and any predictive factors associated with higher success rates.

  Patients and Methods Top

A total of 65 patients who have undergone MAF for complex anal fistula disease at St Vincent's Public and Private Hospital from January 2011 to December 2015 were retrospectively studied. Clinical parameters were obtained from patient's electronic medical records including age, sex, previous attempts of fistula surgery, preoperative seton drainage, type of fistula according to Park's classification, and location of internal opening. The median follow-up was 24.6 months (range: 1–1358 months). Patients were evaluated for fistula recurrence and fecal continence.

This study was descriptive in nature where statistical analysis was described as percentages and mean numbers. Chi-squared test was used to identify clinical variables associated with treatment success. P < 0.05 was considered statistically significant. This study was approved by St Vincent's Hospital Melbourne Quality and Risk Unit.

All patients underwent MAF in lithotomy position with Lone Star™ retractor ring system (CooperSurgical) to obtain access. A partial-thickness flap was raised to include both mucosa and underlying internal anal sphincter. The flap was secured with 3-0 Vicryl™ (Ethicon). All patients received intraoperative intravenous antibiotics, postoperative oral antibiotics, and stool softeners. Patients were discharged postoperatively on the first day.

  Results Top

A total of 65 patients were included in this retrospective study consisting of 22 patients and 43 patients from St Vincent's Public and Private Hospital, respectively, with mean follow-up of 24.6 months (public 6.3 months and private 42.8 months), and the median age of 43 and 44 years, respectively. Nineteen males and 46 females were included in this study where five patients had a history of Crohn's disease. The most common cause of fistula requiring MAF was cryptoglandular fistula-in-ano (82%), with anovaginal fistula (11%), and perianal Crohn's (7%) comprising a minority of the study population.

Furthermore, more than half of the patients (68%) had previous history of anorectal abscess drained, and the majority of patients (91%) had seton insertion before MAF. Seventeen patients had previous fistula surgery before MAF where nine patients underwent fistulotomy, seven patients with partial fistulotomy, and one patient with ligation of intersphincteric fistula tract (LIFT). Imaging of the fistula tract was not routinely performed in our institute; however, 34% of patients had magnetic resonance imaging (MRI) scan and 8% had endoanal ultrasound scan before MAF. The majority of the fistula tracts were transsphincteric in nature with anterior internal opening and seven patients had anovaginal fistulas. Clinical parameters of the study population are described in [Table 1] and fistula characteristics on [Table 2].
Table 1: Clinical characteristics of patients

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Table 2: Fistula characteristics

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The overall healing rate after MAF was 57% in our study where the highest healing rate was observed in the cryptoglandular fistula (66%) group followed by 40% in Crohn's fistula. Only one patient had achieved primary healing from the anovaginal fistula group (14%) as shown in [Table 3]. Furthermore, excluding anovaginal fistula, male population had a higher success rate of MAF compared to female (74% vs. 57%), although it was not statistically significant (P = 0.21). Moreover, MAF performed for an anterior internal opening was associated with higher success rate compared to posterior internal opening (65% vs. 56%, respectively); however, this was also not statistically significant (P = 0.53).
Table 3: Comparison of success rate in different aetiology of fistulas

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A total of 27 patients had recurrence of the fistula after MAF where majority of the recurrence was detected within 3 months of follow-up. Within the patients who had recurrence post-MAF, over half of the patients (16/27; 59%) underwent reinsertion of seton and half of the patients underwent further definitive treatment (14/27; 52%) including fistulotomy, repeated MAF, and LIFT; however, all repeated repair of the fistulas failed. Temporary colostomy was performed in three patients (4.6%). Among the three patients with diverting colostomy, all patients had anovaginal fistula. Sixty-one patients (94%) had normal fecal continence after MAF. This is described in [Table 4].
Table 4: Further definitive treatment post mucosal advancement flap and faecal incontinence rate

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  Discussion Top

MAF has increasingly become the choice of operation for treating complex anal fistulas; however, variable recurrence rates ranging from 10% to 63% have been reported.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10] In our study, the recurrence rate was 43%, which was comparable to existing literature, especially with a low incontinence rate of 6%.

There are many factors which may influence the outcome of MAF and those who reported high recurrence rates or persistent disease were associated with previous attempts of repair.[1],[2],[3],[6],[9] Schouten et al. and Zimmerman et al. showed that success rate was inversely correlated with the number of prior attempts where healing rate was 87% and 78% in patients with no or only one previous attempt of repair; however, in patients with multiple repairs, the healing rate was only 50% and 29%, respectively.[1],[2] Similarly, in Mizrahi et al.'s study, patients who had three or more repair had a worse outcome with recurrence rate of 75%.[6] This is consistent with our current study where none of the patients achieved successful treatment for their second repair.

Crohn's disease and anovaginal fistulas were significant prognostic factors for poor outcome compared to cryptoglandular fistulas [5],[9],[11],[12],[13] and smoking also significantly impacted on healing rate.[8] This was consistent with our current study where majority of patients with anovaginal fistulas had a poor outcome. Fistulas associated with Crohn's disease were more common in females and were often anovaginal.[6] There are still no definite parameters for success of the MAF; however, increased age, history of incision, and drainage of a perianal abscess before advancement flap and previous placement of a seton drain were positive predictors for MAF.[3] In our study, male sex and anterior internal opening were associated with higher rates of success; however, both were not statistically significant.

Furthermore, successful treatment in fistula-in-ano involves long-term follow-up to assess the outcome of MAF. In most studies, follow-up period was shorter than 24 months; however, van der Hagen et al. conducted a long-term outcome study of perianal fistulas treated with MAF.[7] After 12, 48, and 72 months post-MAF, the fistula had recurred in 22%, 63%, and 63% of the patients, respectively.[7] Thus, the success rate of MAF decreased with time. The main reason for recurrence may be due to not detecting accurate fistulous tract. In our study, posterior internal opening fistulas had a lower success rate, which tends to have a curved fistulous tract, often resembling a horseshoe configuration. Unrecognized extensions of the fistula may result in insufficient drainage and local infection beneath the flap and hence resulting in persistent fistula. MRI is not routinely performed in fistula-in-ano; however, it may be reasonable to suggest its use for posterior internal opening fistulas and complex fistula-in-ano to aid in assessing the fistulous tract.

The incidence of disturbed continence after MAF has been reported to vary between 8% and 35%.[1],[2],[3],[10] In previous studies, repeated dilatation of anal sphincters using Park's retractor has been attributed to deteriorating effect on fecal continence.[1],[10] The mobilization of internal anal sphincter to create the MAF may result in anal canal distortion that may also contribute to decreased continence.

There have been several randomized controlled studies to compare the role of technical factors in MAF outcome. Khafagy et al. compared full-thickness endorectal advancement flap versus mucosal rectal flap where the recurrence rate was 10% vs. 40%, respectively.[9] Similarly in Dubsky et al.,[14] recurrence was reported in 5% in full-thickness rectal wall flap and 35.5% in rectal mucosal flap.[14] The circular muscle layer included in the rectal advancement flap was associated with better outcome.

The limitations of the current study were relatively small number of patients used for our retrospective cohort analysis and lack of a scoring method to assess fecal continence after MAF.

  Conclusion Top

The healing rate and fecal continence post-MAF are comparable to previous published data. However, patient selection may be imperative for MAF as higher failure rate is associated in patients with anovaginal fistulas.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Schouten WR, Zimmerman DD, Briel JW. Transanal advancement flap repair of transsphincteric fistulas. Dis Colon Rectum 1999;42:1419-22.  Back to cited text no. 1
Zimmerman DD, Briel JW, Gosselink MP, Schouten WR. Anocutaneous advancement flap repair of transsphincteric fistulas. Dis Colon Rectum 2001;44:1474-80.  Back to cited text no. 2
Sonoda T, Hull T, Piedmonte MR, Fazio VW. Outcomes of primary repair of anorectal and rectovaginal fistulas using the endorectal advancement flap. Dis Colon Rectum 2002;45:1622-8.  Back to cited text no. 3
Abbas MA, Lemus-Rangel R, Hamadani A. Long-term outcome of endorectal advancement flap for complex anorectal fistulae. Am Surg 2008;74:921-4.  Back to cited text no. 4
Jarrar A, Church J. Advancement flap repair: A good option for complex anorectal fistulas. Dis Colon Rectum 2011;54:1537-41.  Back to cited text no. 5
Mizrahi N, Wexner SD, Zmora O, Da Silva G, Efron J, Weiss EG, et al. Endorectal advancement flap: Are there predictors of failure? Dis Colon Rectum 2002;45:1616-21.  Back to cited text no. 6
van der Hagen SJ, Baeten CG, Soeters PB, van Gemert WG. Long-term outcome following mucosal advancement flap for high perianal fistulas and fistulotomy for low perianal fistulas: Recurrent perianal fistulas: Failure of treatment or recurrent patient disease? Int J Colorectal Dis 2006;21:784-90.  Back to cited text no. 7
Zimmerman DD, Delemarre JB, Gosselink MP, Hop WC, Briel JW, Schouten WR, et al. Smoking affects the outcome of transanal mucosal advancement flap repair of trans-sphincteric fistulas. Br J Surg 2003;90:351-4.  Back to cited text no. 8
Khafagy W, Omar W, El Nakeeb A, Fouda E, Yousef M, Farid M, et al. Treatment of anal fistulas by partial rectal wall advancement flap or mucosal advancement flap: A prospective randomized study. Int J Surg 2010;8:321-5.  Back to cited text no. 9
Mitalas LE, Gosselink MP, Zimmerman DD, Schouten WR. Repeat transanal advancement flap repair: Impact on the overall healing rate of high transsphincteric fistulas and on fecal continence. Dis Colon Rectum 2007;50:1508-11.  Back to cited text no. 10
Kodner IJ, Mazor A, Shemesh EI, Fry RD, Fleshman JW, Birnbaum EH, et al. Endorectal advancement flap repair of rectovaginal and other complicated anorectal fistulas. Surgery 1993;114:682-9.  Back to cited text no. 11
Gustafsson UM, Graf W. Excision of anal fistula with closure of the internal opening: Functional and manometric results. Dis Colon Rectum 2002;45:1672-8.  Back to cited text no. 12
Jones IT, Fazio VW, Jagelman DG. The use of transanal rectal advancement flaps in the management of fistulas involving the anorectum. Dis Colon Rectum 1987;30:919-23.  Back to cited text no. 13
Dubsky PC, Stift A, Friedl J, Teleky B, Herbst F. Endorectal advancement flaps in the treatment of high anal fistula of cryptoglandular origin: Full-thickness vs. mucosal-rectum flaps. Dis Colon Rectum 2008;51:852-7.  Back to cited text no. 14


  [Table 1], [Table 2], [Table 3], [Table 4]


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