Perianal fistulas are one of the most common conditions treated by colorectal and general surgeons.1,2 Although anal fistulas are not life-threatening, they result in debilitating pain and soiling, which negatively affect quality of life.3,4 In most instances, history of perianal abscess precedes fistula-in-ano.1,2,5 Although, 50-70% of patients resolve with surgical drainage, 30-50% progress to develop perianal fistula, which supports the theory that fistulas are commonly caused by cryptoglandular abscesses that fail to heal.1,2,5 However, the progression of abscess to fistula is more common in patients with other underlying conditions, such as Inflammatory Bowel Disease (IBD) or malignancy. 1,2 Thus, addressing the underlying cause is important to preventing recurrence. 1,2
Simple fistulas are low-lying within the anal canal, close to the anal verge, and are associated with low risks of fecal incontinence as they are superficial to the external anal sphincter.5 They can be treated by either fistulotomy or fistulectomy, with high rates of successful outcomes. 5 On the contrary, complex fistulas (CF) are located deeper in the anal canal (or “high” in the pelvis) to include the rectum, and can involve more than 30 % of the circumference of the external anal sphincter. 5 CFs can communicate with adjacent organs, such as the vagina, and often develop in conjunction with a history of radiation or IBD.6 They can also be due to iatrogenic injury after colorectal surgery or obstetric trauma. 5 Because of the diversity of etiologies and complexity of condition, there have been a wide variety of surgical procedures developed to treat CFs, including ligation of the fistula tract (LIFT),7 video-assisted anal fistula treatment (VAAFT),8,9 fistula laser closure (FiLAC),10 and endorectal advancement flap (EAF).11,12 However, these are associate with some risk of fecal incontinence due to manipulation of the tissues around the external anal sphincter. 11,12 While there are non-surgical options, such as fibrin glue, plugs or stem cell pastes, that have minimal risk of fecal incontinence, they have lower success rate compared to surgical options.13,14 Thus, at present, there is no ideal treatment strategy for CF.1,2
EAF is one of the most common procedures performed for CFs. It was first reported by Nobel in 1902 for the treatment of rectovaginal fistulas that commonly resulted from obstetric trauma.11,15 It was later modified using a flap of rectal tissue to close the tract between the source of the fistula deeper in the cryptoglandular tissue and its opening to the anal mucosa.11,15,16 Flaps can be tongue-shaped, rhomboid, or elliptical and can include the rectal mucosa alone, or extend deeper to include the submucosa, partial layers of the internal anal sphincter or the entire thickness of the internal anal sphincter.1,2 Traditionally, the opening of the fistula within the rectum is either left open to heal by secondary intention or closed with simple, interrupted, or figure-of-eight sutures. 11,15,16 In addition to covering with a flap, the fistula tract can be treated with curette or coring out.1,2 Although technically complex, the advantage of the EAF is that the sphincter complex is left intact, and thus, EAF has a lower risk of fecal incontinence when compared to other surgical options.1,2 After study for over a century, EAF has an accepted recurrence rate of 7-48% with a risk of fecal incontinence of 15-20%.1,2 However, the optimal thickness of the flap and technique for CFs fistulas is unknown.
Herein, we describe a novel modification of the EAF procedure along with surgical outcomes in terms of recurrence and fecal incontinence post-surgery. We also examine the factors associated with recurrence.
A retrospective chart review of patients diagnosed with complex rectal or anal fistulas who underwent an EAF procedure by the Principal Investigator between January 2004 and February 2019 was done. This study was approved by the Institutional Review Board under Protocol # 2019-233.
Inclusion and Exclusion Criteria:
Patients who presented with CFs and underwent evaluation for EAF placement were included. A CF was defined according to the Garg Classification of severe fistulas in which fistulotomy should not be attempted (Grade III, IV, V).17,18These included as a high linear transsphincteric fistula according(involving an estimated > 1/3 of the sphincter, a fistula associated with IBD, previous sphincter injury, post radiation exposure or an anterior fistula in a female), a transsphincteric fistula with either abscess, multiple tracts or a horseshoe component or interssphincteric supralevator or extrasphincteric extension.19 Due to discrepancy in fistula classification found historically in the literature, the newer Garg classification was compared to older classification systems (Parks5 and St James University20) to better assess how our population compares to the those previously reported. CFs were diagnosed and initially assessed by physical examination and confirmed by intraoperative exam under anesthesia (EUA). If fistula tract or anatomy was unclear by initial clinical exam, Magnetic Resonance Imaging (MRI) was obtained to further define anatomy and classify the fistula-in-ano and aid with surgical planning. All patients who were included were confirmed by MRI and/or EUA as having CFs, and therefore not amenable to simple fistulotomy.
Patient demographic information including age, sex, race, body mass index (BMI), number and type of previous perianal surgeries, history of smoking, systemic steroid use, immunomodulator or immunosuppressive use, IBD (Crohn’s Disease, Ulcerative Colitis (UC) or indeterminant colitis), Chronic Obstructive Pulmonary Disease, Congestive Heart Failure, Coronary Artery Disease, Type II Diabetes Mellitus, Hypertension, and Chronic Kidney Disease were recorded if listed as a diagnosis within the patient’s chart at the time of initial pre-op clinical evaluation. Immunomodulator or immunosuppressive use was defined as those who before or at the time of surgery received the current FDA approved agents for the treatment of Crohn’s or UC (including, mercaptopurine, azathioprine, infliximab, or any novel monoclonal antibodies), or chemotherapy for alternative cancer, or immunosuppression for a history of solid organ transplantation. The etiology of fistula-in-ano including cryptoglandular, Crohn’s disease, UC, post-obstetric fistula, radiation-induced, untreated carcinoma, or Hidradenitis Suppurativa was noted. Additional information regarding the surgical procedure was noted including date of surgery, date of subsequent follow-up visits and date of last follow-up, presence of recurrence of symptoms post-surgery, and subsequent surgical interventions (such as diversion, fistulectomy or repeat EAF). The presence of fecal incontinence, before and after surgery, was assessed at time of history taking during outpatient clinical exams.
Primary outcomes were fistula recurrence and new-onset fecal incontinence after EAF surgery. Recurrence was defined as “the presence of an abscess or purulent drainage from the primary fistula area after at least 6 weeks of healing from EAF”. Fecal incontinence was defined as “difficulty controlling stools (soiling) during follow-up as described by the patient.”1,2 Fecal incontinence was assessed by thorough history and any complaints of difficulty controlling stool or flatus was extracted from the patient’s medical record. Healing from surgery was defined as absence of pain impairing activities of daily living, drainage, soiling or signs of persistent inflammation consistent with concern for wound infection.
Endorectal Advancement Flap: Technical details
Preoperative and intraoperative patient preparation:
All patients received full bowel preparation prior to surgery. On the day of the surgery, a fleet or saline enema was given to the patient based on tolerability. All procedures were performed in the outpatient setting under spinal or general anesthesia. Patients that had fistulas with an anterior lying internal opening were positioned in a prone jack-knife position, whereas those with a posterior internal opening were placed in a lithotomy position.
Description of the surgical technique:
Initial exposure of the surgical field is provided using a Park’s anal retractor, which is later exchanged for a large or medium-sized Sawyer or Hill-Ferguson retractor to decrease tension on the lateral edges during flap closure. Since local anesthetic injection around the future flap site could potentially compromise flap perfusion, local anesthetic is not administered. The rectal mucosa is dissected using needle-tip electrocautery, ensuring a flap base that is three times wider than the apex of the flap (Figure 1A & 1B). Once the flap is created, the internal opening is closed by imbricating the internal sphincter using multiple transverse interrupted 2-0 Vicryl sutures (Figure 1C). This modification not only serves to close the internal sphincter opening, but it also decreases tension on the flap during the closure. The flap is secured over the center of the defect by suturing the inferior edge of the flap with multiple interrupted 3-0 Vicryl sutures to the internal sphincter and anoderm distally to control the interssphincteric tract (Figure 2 A). Compared to running sutures, interrupted suture placement is believed allow drainage underneath the flap that would otherwise collect and impair healing. The lateral edges of the flap are then closed with 3-0 Vicryl sutures, with lateral bites that measured less than 3mm (Figure 2 B).
All external fistula openings and granulation tissue are debrided in a core-out fashion, and the fistula tract(s) are excised to the border of the external sphincter muscle (Figure 3A, 3B &3C). Post-operatively, patients are instructed to avoid strenuous activity and provided with non-narcotic analgesia for 7 days. Patients are followed-up in the clinic at 1-2 weeks postoperatively and approximately every 3 months thereafter until complete healing. Fiber supplements are provided to maintain regular bowel movements and avoid constipation during post-operative healing.
Continuous data were analyzed for normality using the Shapiro-Wilki’s test. Normally distributed continuous variables were analyzed for statistical significance using Student’s t-test and reported as means with standard deviation, whereas non-normally distributed continuous variables were analyzed for statistical significance using Mann-Whitney U tests and reported as median with 25th-75th interquartile range (IQR). Categorical variables were compared using Pearson chi-squared test. Statistical analysis was performed using StataSE software (StataCorp. 2019. Stata Statistical Software: Release 16. College Station, TX: StataCorp LLC), and statistical significance was defined as alpha <0.05. Figures were created using Adobe Illustrator version 24.0.1.