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Anorectal Fistula
Introduction
Anorectal fistula is an abnormal tract lined by epithelial tissue connecting the anorectum and the area around the anal verge, also known as a fistula in ano, anoperineal fistula, and perianal fistula. This complex clinical condition is characterized by recurrent pain, swelling, purulent discharge, and pruritus, causing significant physical and psychosocial distress to the affected individuals. Cryptoglandular infections are the most common etiology, resulting from suppuration of anal crypts located in the dentate line, leading to anorectal abscess.[1]
Anorectal fistulas can occur following a spontaneous drainage of these abscesses or can form after a surgical drainage of anorectal abscesses.[2] There are various classifications of anorectal fistulas based on the anatomy, relation to the anal sphincters and levators, and presence of suppurative collections. The oldest and most frequently used classification is that of Parks, Gordon, and Hardcastle, described in 1976.[3] The other classifications include the St James University Hospital classification, which is based on magnetic resonance imaging (MRI) findings, and the Garg classification, which also describes fistula severity (see Table 1. Anorectal Fistula Classifications).[4][5]
Table 1. Anorectal Fistula Classifications
| Grade | Park Classification | St James University Classification | Garg Classification |
| I | Intersphincteric | Intersphincter linear tract | Intersphincteric and low trans-sphincteric single tract |
| II | Trans-sphincteric | Intersphincter with extensions or associated abscess | Intersphincteric and low trans-sphincteric multiple tracts, horseshoe, or associated abscess |
| III | Suprasphincteric | Trans-sphincteric linear tract |
IIIa: High trans-sphincteric single tract IIIb: Anterior fistula in a female or any low-grade fistula with comorbid illnesses |
| IV | Extrasphincteric | Trans-sphincteric with extensions or associated abscess | High trans-sphincteric multiple tracts, horseshoe, or associated abscess |
| V | Supralevator and translevator extension | Suprasphincteric or extrasphincteric fistula |
The American Gastroenterology Association has proposed a simpler classification that is clinically applicable and helps guide treatment selection.[6] According to this classification, anorectal fistulas are categorized as simple and complex based on the number of tracts, anatomical location of the internal opening and the tract, involvement of the external anal sphincter, etiology of the fistula, and recurrence. Cryptoglandular fistulas that are intersphincteric and low trans-sphincteric and that are not recurrent are termed as simple fistulas. High trans-sphincteric, suprasphincteric, and extrasphincteric tracts; those with associated abscesses; noncryptoglandular etiologies such as Crohn disease, malignancy, radiation-related disease, and tuberculosis; deficient sphincter function; anterior tracts in females; and recurrent fistulas are classified as complex.[7]
The evaluation consists of a detailed history and a thorough clinical examination to identify the location of the internal opening, number and locations of external openings, associated abscesses, possible etiology, and the integrity of the external anal sphincter. For simple anorectal fistulas, further investigations such as endoscopy, MRI, or endoscopic ultrasound are seldom necessary. Complex fistulas require these tests to delineate the anatomy and identify the possible etiology, which can be addressed before or during fistula management.[8]
There are various treatment options for anorectal fistulas. Examination under anesthesia and fistulotomy remain the gold standard procedure for simple fistulas. The risk of sphincter injury and incontinence makes this operation not ideal for complex fistulas, which either require staged fistulotomy or sphincter-saving procedures.[9] This course discussion explains the epidemiology, etiopathogenesis, clinical evaluation, diagnosis, management, and complications of anorectal fistulas with an additional emphasis on patient education and measures to enhance healthcare outcomes.
Etiology
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Etiology
Cryptoglandular
This is the most common etiology of anorectal fistulas, constituting up to 90% of cases.[1] This type results from infection of the proctodeal glands located in the intersphincteric space at the level of the dentate line.[10] Anorectal abscesses also occur secondary to cryptoglandular infections and are associated with a concomitant fistulous tract in 30% to 70% of patients. Of those who do not have a fistula, 30% to 50% will develop one during the follow-up.[11]
Inflammatory Bowel Diseases
Crohn disease is more commonly associated with anorectal fistula formation compared to ulcerative colitis. The incidence of anorectal fistulas in patients with Crohn disease is approximately 34%, and these are often complex with multiple tracts, associated abscesses, and high recurrence rates.[12]
Trauma
Trauma-induced anorectal fistulas are often iatrogenic, with the most common being hemorrhoidectomy.[13] The other causes include obstetric anal sphincter injuries that can lead to perineal and rectovaginal fistulas. Complicated vaginal deliveries with third or fourth degree perineal tears, instrumental deliveries, cephalopelvic disproportion, absence of skilled birth attendant, and precipitate labor are the risk factors.[14]
Infections
Anorectal fistulas are rarely a presentation of anal tuberculosis and should be suspected in endemic regions or nonhealing recurrent fistulas. Using polymerase chain reaction on pus samples is more sensitive than histopathology for detecting tuberculosis.[15][16] Sexually transmitted infections, such as gonorrhea, chlamydia, syphilis, and herpes, are usually seen secondary to anal receptive intercourse, which may predispose individuals to perianal abscess and fistulas.[17] Patients with HIV, with or without AIDS, can develop anorectal diseases, including anorectal fistulas, which constitue 6% of anorectal pathologies, regardless of the use of antiretroviral therapy.[18]
Malignancy
Anorectal adenocarcinomas can often present with fistulas, especially in patients with Crohn disease who carry an additional risk of developing anal adenocarcinoma. Similarly, squamous cell carcinoma of the anal canal can also lead to anorectal fistulas.[19]
Radiation
Radiation proctitis is another cause of anorectal fistulas, which occurs following pelvic irradiation for anorectal, cervical, and prostate cancers.[20] This condition poses a significant management challenge due to poor wound healing, tissue fibrosis, and decreased vascularity. The fistulas are often complex with distortion of the anorectal architecture, sphincter dysfunction, and other associations such as rectourethral, rectovaginal, and rectovesical fistulas.[21]
Congenital
Anorectal malformations can be associated with congenital fistula, with a prevalence of 1 per 10,000 live births. Among the anal anomalies, congenital anal fistula is seen in 14% of patients and is more common in females, and is often associated with supralevator anal atresia.[22]
Epidemiology
Anorectal fistula is a common anorectal condition encountered in general and colorectal surgical practice. However, its true prevalence is difficult to estimate, and the reported data is available only from authors' and single-institutional experiences. In the United States, the prevalence of anorectal fistula is 0.69% to 5%, with approximately 34% of the patients having a concomitant anorectal abscess. In patients who undergo drainage of anorectal abscesses, 26% to 37% develop a fistula during follow-up.[23]
In Europe, the prevalence is reported to be 1.04 to 2.32 per 10,000 people per year, with an overall prevalence of 18.37 per 100,000 population.[24][25] The most common etiology is cryptoglandular, accounting for over 90% of the cases, followed by inflammatory bowel diseases, particularly Crohn disease, malignancies, trauma, tuberculosis, and radiation proctitis-associated fistulas.[26] Anorectal fistulas are twice as common in men as in women and are common between the ages of 20 and 60. Acquired anorectal fistulas are very uncommon in children.[23] The predisposing factors include obesity, diabetes, hyperlipidemia, a history of anorectal surgery, a sedentary lifestyle, poor personal hygiene, and smoking.[27][28][29][30]
Pathophysiology
The pathophysiology of anorectal fistulas varies with the underlying etiology. Cryptoglandular fistulas almost always develop from suppurative infections of the anal crypt glands, resulting from various risk factors mentioned above. Obstruction of the openings of these glands causes stasis of secretions, which then become secondarily infected, resulting in an abscess. The pathway of the spread of the abscess determines the type and complexity of the fistula. While intersphincteric fistulas are the most common type, where the internal (anal crypt at the dentate line) and external openings are connected by a tract lined by granulation tissue between the internal and external anal sphincters, trans-sphincteric, suprasphincteric, and extrasphincteric fistulas traverse either the external anal sphincter or the levators, making their management complex.[31]
Fistulizing perineal Crohn disease-related fistulas are formed by 2 mechanisms: epithelial to mesenchymal transition, which involves the transformation of epithelial cells into mesenchymal-type cells that can migrate and infiltrate adjacent tissues, and matrix metalloproteinases, which are enzymes that break down various components of the extracellular matrix. The other theories include fecal microbiota and genetic alterations that contribute to the formation of anorectal fistulas in patients with Crohn disease.[32][33][34] Malignant anorectal fistulas occur due to the obstruction of proctodeal glands by malignant cells, such as in squamous cell carcinoma of the anal canal, or by direct infiltration of the tumor into the perirectal tissue, resulting in abscess and fistula formation.[19]
Radiation proctitis leads to delayed tissue healing, reduced vascularity, obliterative endarteritis, and fibrosis, which can result in complex anorectal fistulas.[20] Tuberculous anorectal fistulas occur due to the dissemination of the tubercle bacilli into the anal canal via hematogenous spread from the lungs, ingestion of infected bacilli from the sputum, direct spread from adjacent organs, or lymphatic spread. The infection leads to caseous necrosis, often producing complex branching tracts with associated abscesses.[35]
Histopathology
Simple anorectal fistulas with cryptoglandular etiology show features of chronic inflammation with granulation tissue, and do not mandate histopathological confirmation. However, histologic analysis should be considered in complex and recurrent fistulas and in cases with atypical etiologies, such as Crohn disease, tuberculosis, malignancy, or radiation-induced fistulas. The histopathological features of Crohn disease-related anorectal fistulas include cryptitis, crypt distortion, nonnecrotizing granulomas, giant cells, and acute and chronic inflammatory granulation tissue.[36] Fistulas secondary to anorectal cancers show neoplastic tissue with prominent nuclei, a high nucleus-to-cytoplasm ratio, and other differentiations, such as squamous cell carcinomas, adenocarcinomas, neuroendocrine tumors, and malignant melanomas.[37] Tuberculous anorectal fistulas demonstrate caseation necrosis, Langhans giant cells, epitheloid cells, and granulomas.[38]
History and Physical
A thorough history, complete review of systems, and physical examination are the first steps in the evaluation of anorectal fistula. Typical symptoms of anorectal fistulas include perianal pain, discharge, pruritus, and skin irritation. Red flag signs and symptoms, such as rectal bleeding during defecation, altered bowel habits, passage of mucus, tenesmus, and weight loss, are not common in cryptoglandular anorectal fistulas, and such patients warrant a colonoscopy and other additional tests to rule out more sinister etiologies such as colorectal cancers and inflammatory bowel disease. Previous history of anorectal abscesses, including their management, complications, and recurrences, should be evaluated.
Patients with inflammatory bowel diseases, especially Crohn disease with perineal complaints, should be questioned regarding the duration, management, and complications related to the disease process. In addition, patients with long-standing inflammatory bowel disease should be evaluated for colorectal cancer. A history of malignancy or radiation to the pelvis is essential, as fistulas from anorectal cancers and radiation are well-documented, and treatment should be coordinated with the patient’s cancer care.
A history of rash or high-risk sexual behavior should prompt suspicion of STIs. A patient with a chronic cough, weight loss, or a history of pulmonary tuberculosis presenting from an endemic area with a complex anorectal fistula should be evaluated for tuberculous fistula. Similarly, draining fistulas, those in abnormal locations, and chronic or recurrent fistulas should raise concern for a systemic process.[39]
The general examination should focus on evaluating systemic conditions. Patients with malignant etiologies causing anorectal fistulas often have advanced cancers and display signs of cachexia, anemia, and malnutrition. Peripheral signs of inflammatory bowel disease, such as aphthous stomatitis, subcutaneous nodules, erythema nodosum, and pyoderma gangrenosum, should raise suspicion of fistulizing perineal Crohn disease.[40]
Tuberculous fistulas can have other extrapulmonary manifestations such as lymphadenopathy, scrofuloderma, sinuses, and ulcerations.[41] Abdominal examination is important, especially in patients with Crohn disease, anorectal cancers, and intestinal tuberculosis. Palpable abdominal masses, tenderness, guarding, and features of intestinal obstruction should be assessed to guide appropriate management.
Perianal examination is the most crucial aspect of evaluation in anorectal fistula. The examination should be conducted in a well-lit room with adequate exposure and allowing privacy. The number of external openings, their locations, distance from the anal verge, associated abscesses, and any healed scars or openings should be examined.
The internal opening is found on a digital rectal examination (DRE) as a firm, indurated area, mostly along the dentate line. The Goodsall rule is a clinical tool used to predict the location of the internal opening based on the external opening, with up to 75% accuracy.[42] As per this rule, anterior fistulas with external openings within 3 cm from the anal verge have a radial tract and an internal opening corresponding to the clock position of the external opening.
In contrast, posterior fistulas and those with external openings greater than 3 cm away from the anal verge have a curvilinear tract that opens into the internal opening posteriorly at 6 o'clock—the fistulous tract, especially when intersphincteric or low trans-sphincteric, can be palpated on perianal examination. DRE should also assess the integrity of the external anal sphincter, an intersphincteric abscess, felt as a boggy, tender swelling, previous scars, and luminal stenosis. Anoscopy is not an essential tool in the examination of anorectal fistula, as it provides no additional information beyond the DRE and is used only in patients suspected of hemorrhoidal disease or anal polyps in addition to the fistula.
Evaluation
The evaluation includes laboratory studies, imaging, endoscopy, and anorectal manometry. Radiological studies form the cornerstone of the evaluation of anorectal fistula. As mentioned above, not all patients require radiological studies; these are reserved for those with complex fistulas, noncryptoglandular etiologies, recurrent fistulas, or fecal incontinence. Imaging studies include EUS, MRI, and computed tomography (CT) of the pelvis with fistulography. These help accurately determine the location of the internal opening, orientation, branching, and relationship of the tracts to the external sphincter, identify abscesses, and the primary etiology, such as Crohn disease or anorectal cancers.
Laboratory Findings
Basic laboratory panels should be obtained in patients, including a complete blood count and a comprehensive metabolic panel. Low hemoglobin may indicate underlying anemia, which could be secondary to inflammatory bowel disease or a gastrointestinal malignancy. Leukocytosis and elevated C-reactive protein levels may reveal an underlying infectious process, occult abscess, or active Crohn disease. Erythrocyte sedimentation rate and Mantoux test should be considered in patients with suspected tuberculous fistula, and appropriate serological tests for sexually transmitted infections.
Endoscopic Ultrasound
Endoscopic ultrasound, EUS, and transperineal ultrasound are useful modalities in the evaluation of complex anorectal fistulas. EUS is valuable in delineating the fistula anatomy and its relationship with the external anal sphincter and the presence of abscesses. This modality is cost-effective, quick, and easy to perform, with accuracy similar to MRI in identifying internal openings, abscesses, and intersphincteric and transsphincteric tracts.[43][44][45][46][47] The introduction of hydrogen peroxide into the external fistulous opening canal improves the accuracy of endoanal ultrasound in identifying both fistulous tracts and occult abscesses.[48] However, its operator dependence and inability to be reinterpreted by other radiologists and surgeons based on the images make it less preferred than MRI.[49]
MRI
MRI is the gold standard imaging modality for anorectal fistulas. This modality has an accuracy of up to 100% in identifying the internal opening, primary and secondary tracts, abscesses, horseshoe tracts, and the relation to the anal sphincter.[50][51][52][53][54] MRI is crucial in the evaluation of complex fistulas, especially the suprasphincteric, extrasphincteric, and horseshoe fistulas.
Study results have shown that preoperative MRI in complex fistulas aids in developing an appropriate operative plan by providing the surgical team with a detailed, thorough understanding of fistula anatomy.[55] This results in effective management, the choice of the most appropriate surgical technique, and reduced complications such as sphincter injury and recurrence of anorectal fistulas. The various MRI sequences include T2 spectral attenuated inversion recovery, short tau inversion recovery, turbo spin echo, and fast field echo, acquired in coronal, sagittal, and axial planes.[56]
To harmonize the reporting and description of anorectal fistulas on an MRI, various classification systems and guidelines have been described. The St James University Hospital system was the first to classify anorectal fistulas into 5 types based on severity.[57] The others include the Garg system of classification, Structured MRI, and Endoanal Ultrasound Anal Fistula Reporting Template (SMART), and the height of penetration of the external anal sphincter (HOPE) systems. MRI also plays a crucial role in postoperative monitoring and follow-up by accurately assessing healing of the internal opening and the intersphincteric part of the tract in up to 99.2% of cases.[58]
CT and CT Fistulogram
CT is useful for identifying abscesses and drainable fluid collections, as it is quick and readily available in most clinical scenarios. However, its routine use in the evaluation of anorectal fistulas is not recommended due to its inaccuracy, the need for a contrast injection, and radiation exposure. MRI and EUS are superior to CT scans for the identification and classification of anorectal fistulas. The current use of CT scans is limited only to cases where MRI is not available or as a routine CT for imaging of the abdomen and pelvis, such as intestinal Crohn disease, tuberculosis, and postoperative complications after rectal resections.[8]
Endoscopy
In patients with suspected Crohn disease, malignancy, and tuberculosis, colonoscopy should be considered to rule out involvement of the rest of the colon and terminal ileum. Endoscopy can also help determine fistula complexity, mucosal involvement, and associated stenosis, strictures, or abscesses.[59]
Anorectal Manometry
Anal manometry objectively assesses the function of the internal and external sphincters by measuring resting and squeeze pressures, respectively, and evaluates the integrity of the continence mechanism using the water-holding and balloon expulsion tests. The routine use of anal manometry before surgeries for anorectal fistula has been shown to reduce the incidence of fecal incontinence and recurrence rates. This test should definitely be considered in patients with preoperative fecal incontinence, recurrent operations, and with high trans-sphincteric, suprasphincteric, and extrasphincteric fistula tracts.[60]
Treatment / Management
Medical Management
Medical management is mostly reserved for patients with Crohn disease and advanced anorectal malignancies, and is sometimes combined with the placement of draining setons.[61] Aminosalicylates and corticosteroids, which are commonly used first-line agents for intestinal Crohn disease, are ineffective for perianal fistulizing disease. Biological agents such as anti-tumor necrosis factor alpha drugs (infliximab) and monoclonal antibodies like adalimumab and ustekinumab remain the cornerstone of medical management. These are often combined with antibiotics such as ciprofloxacin and metronidazole when a concomitant abscess is present.[39](A1)
Surgical Management
The management of anorectal fistula is almost always surgical, and the choice of therapy depends on the etiology, type, and complexity of the fistula, as well as the integrity of the anal sphincter (see Table 2. Surgical Procedures for Anorectal Fistulas). Examination under anesthesia and fistulotomy are the most common surgical procedures and are still considered the gold standard treatment for intersphincteric and low trans-sphincteric fistulas. The other options include staged fistulotomy with seton placement, fistulectomy with sphincter reconstruction, and sphincter-preserving procedures such as ligation of the intersphincteric fistula tract (LIFT), fibrin glue, fistula plug, fistula laser-assisted closure (FiLac), video-assisted anal fistula treatment (VAAFT), and endorectal advancement flaps (ERAF). The newer modalities include transanal opening of the intersphincteric fistula space (TROPIS), platelet-rich plasma therapy, stem cell therapy, and photodynamic therapy.[9][8](A1)
Table 2. Surgical Procedures for Anorectal Fistulas
| Procedure | Indications | Technique | Success Rates | Complications |
| Fistulotomy | Intersphincteric and low trans-sphincteric fistulas | Examination under anesthesia (EUA) to identify the internal opening. The tract is probed and laid open to heal secondarily. | 95% to 100% | Sphincter injury, recurrence |
| Fistulectomy and sphincter reconstruction | High trans-sphincteric, suprasphincteric, extrasphincteric, horseshoe, and anterior fistulas in women (complex fistulas) | The fistula tract is completely excised, dividing the external anal sphincter, which is then formally repaired in single or multiple layers. | 90% to 95% | Wound breakdown and failure of repair, sphincter injury, recurrence |
| Partial fistulotomy and seton placement | Complex fistulas and Crohn disease-related fistulas | EUA is done to identify the fistula tract, which is laid open partially to preserve most of the external anal sphincter, and a seton is placed around the residual tract. | 94.4% | Sphincter injury, postoperative pain, need for repeated procedures, and longer healing time |
| Device-based sphincter-saving procedures (fibrin glue, fistula plug, over-the-scope clip) | Complex fistulas |
EUA is done, and the external opening is occluded using either fibrin glue or a fistula plug. Over-the-scope clips are used to occlude the internal opening. |
20% to 55% | High failure rates and recurrence |
| Ligation of the intersphincteric fistula tract (LIFT) | Complex fistulas | EUA is done, and the intersphincteric portion of the fistula tract is identified, which is then sutured closed to the internal opening and divided. BioLIFT involves incorporating a bioprosthetic graft into the tract, in addition to LIFT. | 76% | Failure, recurrence, sphincter injury, and expulsion of the graft |
| Fistula Laser-assisted closure | Simple and complex fistulas | EUA is done, and the internal opening is closed; the laser fiber is passed through the external opening to ablate the tract. | 63% | Recurrence, infections |
| Video-assisted anal fistula treatment | Complex and recurrent fistulas | EUA is done, and a fistuloscope is passed through the external opening, identifying the tract and its branches, which are debrided with an endobrush, and the tract is ablated using diathermy or laser. Finally, the internal opening is sutured. | 71.2% to 87.1% | Recurrence, infections |
| Endorectal advancement flap | Complex and recurrent fistulas | Usually performed to drain fistulas or to place a seton. The external opening is cored out and left open to drain. The internal opening is sutured, and a rectal mucosal or a full-thickness flap is raised to cover the internal opening. | 66% to 87% | Failure, infections, recurrence |
| Transanal opening of the intersphincteric space | Complex and recurrent fistulas | EUA is done, and the intersphincteric space is accessed transanally through the internal opening, which is then laid open and left to heal by secondary intention. The lateral part of the tract is either curetted or ablated using a laser. | 86% to 93% | Recurrence, incontinence |
| Platelet-rich plasma (PRP) and stem cell therapy | Complex and recurrent fistulas | EUA is done, the internal opening is sutured, and the external opening is curetted. The tract is injected with either freshly prepared PRP or stem cells | 50% to 62.4% | Recurrence |
| Photodynamic therapy | Complex and recurrent fistulas | Photo-oxidative damage is induced in the fistula tract using the photosensitizers in the light energy | 65.3% to 80% | Recurrence |
Differential Diagnosis
The differential diagnosis for anorectal fistulas includes the following:
- Anal fissure
- Presents with painful defecation and passage of drops of fresh blood. The presentation can mimic an intersphincteric abscess with a fistula. Clinical examination does not reveal any external opening, and there will be severe anorectal spasm on DRE.[62]
- Thrombosed or strangulated hemorrhoids
- Patients present with perianal pain and swelling that is not reducible. There can be a prior history of hemorrhoidal disease, such as painless bleeding towards the end of defecation and a mass descending per rectum. Clinical examination reveals a tender, boggy swelling at the anal verge, which can be confused with a perianal abscess.[63]
- Solitary rectal ulcer syndrome
- THis condition is seen in patients with obstructive defecation syndrome, causing rectoanal intussuception. Presenting complaints are usually perianal pain, constipation, sensation of incomplete evacuation, and bleeding during defecation. DRE reveals an indurated rectal mucosa mostly involving the anterior wall.[64]
- Perianal abscess
- Presents with severe perianal pain, swelling, warmth, and induration. Perineal examination will not reveal any external opening. However, an internal opening can be identified in up to one-third of the patients.[65]
- Anal cancer
- Squamous cell carcinoma of the anal canal and the perianal skin, and anorectal adenocarcinoma present with ulceroproliferative growth at the anal verge associated with pain, bleeding, discharge, and fecal incontinence. Clinical examination, imaging, and histopathological examination confirm the diagnosis.
- STIs
- They include gonorrhea, chlamydia, syphilis, herpes, and HIV infections. The clinical features include anorectal pain, tenesmus, pruritus ani, perianal vesicles and other skin lesions, and inguinal lymphadenopathy.
- Perianal Crohn disease without fistulization
- Perianal Crohn disease presents in a variety of ways. Apart from complex anorectal fistulas, perianal abscesses, fissures, ulcerations, and anorectal malignancies can be seen in patients with perianal Crohn's disease.
Prognosis
The prognosis of anorectal fistulas varies depending on the etiology, fistula type, prior surgical management, and patient comorbidities. In anorectal fistulas of cryptoglandular origin, healing rates for simple fistulas approach 80%, and complex fistulas are around 60% for sphincter-preserving operations. Setons have been used with great success, achieving 6-month healing rates of 80% to 90%.
However, setons removed too early may lead to incomplete healing if the tract has not migrated sufficiently to allow healing. These fistulas require a seton exchange 1 or multiple times. A fistula that fails to heal by 12 weeks is considered a treatment failure, and if a previously healed fistula starts discharging within a year, it is deemed to have recurred.[66] Treatment failure and recurrence are the important prognostic features affecting the outcomes in patients with anorectal fistulas.
Causes for failure of surgical therapy include failure to identify the internal opening and incomplete division of the fistula tract in a fistulotomy.[67] In the LIFT procedure, leaving a long fistula tract behind and incomplete ligation of the tract are possible causes of failure. In ERAF, the success of the procedure depends on the integrity of the flap.
If the flap fails, either due to poor vascularity, persistent infection and inflammation at the internal opening as seen in Crohn disease, or patient risk factors such as smoking, immunocompromised states, or diabetes mellitus, the fistula will recur.[68][69] Device-based sphincter-saving procedures for anorectal fistulas, such as fibrin glue and fistula plugs, have higher failure rates. The causes for failure include incomplete occlusion of the internal and external openings, incomplete debridement of the fistula tract, and premature dislodgement of the fistula plug.
Depending on the initial procedure performed, additional procedures are used to treat recurrent fistulas. Most sphincter-saving procedures, such as LIFT, FiLac, VAAFT, and ERAF, are performed after an initial procedure, often involving examination under anesthesia (EUA) and seton placement. When a fistula recurs or fails to heal, it is useful to perform an endoanal ultrasound or an MRI to characterize the tract and delineate the anatomy before EUA.
Due to the risk of incontinence with repeated anorectal surgeries, a sphincter-preserving approach is best utilized in the treatment of recurrent fistulas, mainly if a fistulotomy or fistulectomy was the primary treatment. The LIFT procedure is an option for recurrent fistulas; other options include FiLac, VAAFT, and ERAF, which can be combined with LIFT. These procedures can be repeated in combination with other modalities such as bioprosthesis insertion or stem cell therapy when required.[70]
Complications
Complications of anorectal fistulas include perineal sepsis, necrotizing soft tissue infections, and fourneir's gangrene. The prolonged nature of illness, chronic and recurrent symptoms, can pose a significant psychosocial burden on the affected individuals, resulting in severe depression. Complications of surgeries for anorectal fistulas include bleeding, incontinence to stools or flatus, perineal sepsis, anal stricture, and recurrence. The risk factors for recurrence include high transanal fistula, horseshoe extensions, multiple branching tracts, and failure to identify the internal opening during the procedure.[67] Complex etiologies such as Crohn disease, tuberculosis, radiation proctitis, and anorectal cancers lead to higher recurrence rates.
Risk Factors for fecal incontinence after surgeries for anorectal fistulas include a previous history of anorectal procedures, especially fistulotomy or fistulectomy, anterior fistulas in females, complex fistulas, and preoperative incontinence.[66][71] Anorectal manometry is a useful objective tool for assessing anal sphincter function and the continence mechanism. Low resting pressure indicates poor resting anal tone that is reflective of internal sphincter dysfunction. Similarly, decreased squeeze pressures, inability to sustain squeeze, and failure of balloon expulsion tests indicate dysfunction of the external anal sphincter.
Performing anorectal manometry preoperatively can help guide the choice of the appropriate surgical procedure, especially in patients with complex and recurrent fistulas.[72] Treatment of minor incontinence to flatus and stools involves biofeedback therapy and physiotherapy such as Keigle exercises. Major incontinence necessitates sacral nerve stimulation or sphincter reconstruction.[73]
Postoperative and Rehabilitation Care
Anorectal fistula requires comprehensive postoperative and rehabilitation care. When a fistulotomy or a seton is placed, it is important to teach patients to digitate the wound and gently tug the seton at regular intervals until the wound heals. Wound digitization prevents premature approximation of the skin edges and allows the wound to granulate and heal from within, thus reducing the risk of fistula recurrence.
Similarly, frequent tugging on the seton will aid migration of the tract to more superficial layers, making seton exit feasible and avoiding multiple seton exchanges.[69] Sitz bath helps by providing comfort and pain relief through thermoregulatory mechanisms and should be advised postoperatively for all patients undergoing surgeries for fistula. Patients who have undergone fistulotomy for trans sphincteric fistulas should be taught Keigle exercises to restore the strength and function of the external anal sphincter.[74]
Deterrence and Patient Education
Anorectal fistulas pose a considerable psychosocial and financial burden on affected individuals due to their distressing symptoms, complex procedures, and high chances of recurrence. Patient education is crucial in achieving optimal outcomes. First and foremost, patients should be counseled regarding the nature of the illness, whether it is a simple or complex fistula, possible underlying etiology if known, and investigative modalities such as EUA and MRI pelvis to delineate the fistula anatomy and plan the most appropriate surgical procedure. Simple cryptoglandular fistulas do not warrant any prior imaging, and such patients can be considered for EUA and fistulotomy, which can achieve high cure rates. Those with complex and recurrent fistulas need to be informed regarding the need for preoperative workup, available surgical options, their success rates, and the complications.
As described above, postoperative care and rehabilitation play a pivotal role in achieving successful outcomes after surgery. The importance of perineal hygiene, wound digitization, seton care, and a healthy bowel habit should be emphasized. Complications such as infection, reactionary or secondary hemorrhage, and transient incontinence to stools and flatus should be explained to all patients. Finally, a healthy lifestyle that includes exercise, a healthy diet, prevention of constipation, and management of comorbid conditions such as diabetes mellitus should be encouraged. Certain high-risk groups, such as patients with Crohn disease, gastrointestinal tuberculosis, radiation proctitis, anorectal malignancies, and STIs, should be warned regarding the symptoms of anorectal fistulas and should be advised to seek immediate care when necessary.
Enhancing Healthcare Team Outcomes
Management of anorectal fistula is often challenging due to its multiple etiologies, varied presentations, challenging complications, numerous treatment modalities, different outcomes, and higher recurrences. The care of patients with anorectal fistulas necessitates a collaborative approach including general and colorectal surgeons, pelvic floor physiotherapists, anorectal manometry technicians, nurses, pharmacists, advanced care practitioners, and other health workers. Clinicians should equip themselves with sufficient knowledge to accurately diagnose anorectal fistulas, differentiate between simple and complex cases, identify the underlying etiology, and initiate appropriate referral pathways. General surgeons can effectively manage simple cryptoglandular fistulas. However, complex and recurrent fistulas benefit from consultation with a colorectal surgeon and treatment. Patients with Crohn disease should be managed by a multidisciplinary team consisting of gastroenterologists, nutritionists, and surgeons to achieve optimal outcomes.[75][76]
Patients should be thoroughly counseled regarding the treatment modalities, outcomes, and complications. In case of recurrence, evaluation should aim to identify a noncryptoglandular etiology and delineate the correct anatomy of the fistula tract using endoanal ultrasound, magnetic resonance imaging, and, if required, colonoscopy. Care coordination plays a pivotal role in ensuring that the patient's journey from initial presentation through treatment and follow-up is well-managed and safe. By embracing these principles of skill, strategy, ethics, responsibilities, interprofessional communication, and care coordination, healthcare professionals can deliver patient-centered care, ultimately improving patient outcomes and enhancing team performance in the management of anorectal fistulas.
References
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