A randomised study to compare the results of the anal fistula plug (AFP) with the endorectal advancement flap (ERAF) in the treatment of high fistula-in-ano of cryptoglandular origin
The use of lyophilised porcine submucosal plugs (Cook Surgisis®, AFPTM) has been proposed as an alternative to conventional surgical techniques for the treatment of anal fistulas. Rates of favourable outcomes are highly variable in the literature (between 13.9% and 87%). Unfortunately, some reports are retrospective studies, others are prospective cohort studies, and only one study has compared the efficacy of this technique with a retrospective review of patients treated with endorectal advancement flap (ERAF). Additionally, these studies include simple and complex anal fistulas, anovaginal fistulas and patients with inflammatory bowel disease. So far, there is not a randomised study comparing the AFP with other surgical procedures suitable for high fistulas. Therefore, the objective of this randomised study was to compare the results of AFP with ERAF in the treatment of high fistula-in-ano of cryptoglandular origin.
The Comité Ético de Investigación Clínica of the Health Department of the Government of Navarra (Spain) gave approval on the 2nd April 2007 (ref: Pyto. 14_07).
Interventional randomised single-centre trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
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Fistula-in-ano of cryptoglandular origin
All patients underwent full mechanical bowel preparation and received antibiotic and antithromboembolic prophylaxis. The patients were operated on under general anaesthesia in the lithotomy position. Surgical procedures were performed by two surgeons with accredited degrees in Coloproctology (ESBQ Coloproctology).
Anal fistula plug (AFP):
The plug was submerged in saline for two minutes; the internal fistula orifice was located by injecting hydrogen peroxide. Curettage of the track was not performed. A probe was inserted in the fistula track. The AFP was placed into the tract until resistance was felt and then fixed in place with a 2-0 polyglactin suture (Vicryl®) which included the internal sphincter. The suture was tied in order to close the internal opening of the fistula over the plug. Care was taken to ensure that the external orifice of the fistula was not completely occluded in order to allow the track to drain. The remaining plug was cut at the level of the external opening.
Endorectal advancement flap:
The tract of the fistula was completely excised, including the internal opening. A rectal flap above the internal opening was mobilised, including the mucosa and submucosa, with a 3 to 4 cm broad base. The rectal flap was mobilised sufficiently to cover the internal opening. Exhaustive haemostasis was performed to avoid a haematoma under the flap. Finally, the flap was sutured to the edge of the anal canal, covering the internal opening.
Average duration of treatment:
Anal Fistula Plug: 30 minutes
Endorectal Advancement Flap: 90 minutes
Total duration of follow-up for all arms of your trial: one year
Primary outcome measures
Fistula closure rate; recurrence is defined as the presence of an abscess arising in the area, or by obvious evidence of fistulation. Evaluated at 2, 4, 8, 12 weeks after surgery, and at 6, 9 and 12 months.
Secondary outcome measures
Continence, evaluated pre- and post-operatively (after one year) using the Wexner score.
Overall trial start date
Overall trial end date
Participant inclusion criteria
1. Aged above 18 years, either sex
2. High fistula-in-ano of cryptoglandular origin (the fistulas were defined as high when they included the upper two-thirds of the external sphincter complex)
3. Informed consent
Target number of participants
186 patients (93 in each group)
Participant exclusion criteria
1. Secondary tracts
2. Horseshoe fistulas
3. Anovaginal fistulas
4. Rectouretral fistulas
5. Human immunodeficiency virus (HIV)-positive patients
6. Diagnosed from Crohn's disease
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
C/Trinidad Fernandez Arenas
Hospital Virgen del Camino (Spain) - Public University of Navarra
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Results - basic reporting