Anal and Rectal Fistula: Clinical Guidelines

List of Abbreviations

CD – Crohn's disease

CI – confidence interval

ZAPK — sphincter apparatus of the rectum

MRI – magnetic resonance imaging

CT — computed tomography

MSK — mesenchymal stem cells

RCT – randomized controlled trial

SZP — anal fistula

LCE – level of confidence of evidence

GRS – grade of recommendation strength

US – ultrasound examination

Terms and Definitions

Sphincter-sparing surgery — surgery in which no trauma occurs to the sphincter apparatus of the rectum, or the impact on the sphincter apparatus is minimal and does not lead to clinically significant impairment of bowel content continence.

Non-healing of a fistulous tract – persistence or recurrence of communication between the rectal lumen and the wound or fistulous tract following surgery for a fistula (typically, this term is used in sphincter-sparing treatments where the fistulous tract may not be completely excised, and the internal opening is closed using one of the plastic repair techniques). This term differs from "recurrence" in that the wound or fistulous tract does not have time to heal completely before communication with the rectal lumen is re-established.

Fistula recurrence – reappearance of an anal fistula some time after a successful operation, i.e., complete healing of the fistulous tract (provided that the internal fistula opening is localized in the same place as before the surgery).

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Anal fistula – a pathological tract between the anal canal and surrounding tissues and/or organs and/or perianal skin.

In this case, the internal opening of the fistula is an inflamed anal crypt; therefore, an anal fistula without further specification generally implies a fistula of cryptoglandular origin. In other cases, the etiology of the anal fistula is specified additionally (post-traumatic fistula, post-radiation fistula, etc.).

The external fistula opening is most frequently located on the skin of the perianal region, perineum, or gluteal region. Much less commonly, the fistula opens into the vagina, urethra, and other pelvic organs. An anal fistula can also be an incomplete internal one, meaning it ends blindly in the soft tissues [1,2].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

The formation of an anal fistula of cryptoglandular origin is associated with the patterns of spread and persistence of the purulent-inflammatory process from the anal crypts along the course of the anal glands. Approximately 95% of anal fistulas are related to a history of acute paraproctitis. Most anal glands end blindly in the intersphincteric space or submucosal layer. Significantly less often, the glands are located between the circular and longitudinal muscle layers of the rectal wall or pass through the external sphincter [1-4].

During the formation of an anal fistula, an internal fistula opening forms in the area of the affected anal crypt, acting as the portal of entry for infection that maintains the chronic inflammatory process. Meanwhile, the purulent tract is surrounded externally by fibrous tissue, forming the fistulous tract. Along the course of the fistula within the adipose tissue, infiltrates, tracking abscesses, and purulent cavities may form if drainage is inadequate [2].

1.3 Epidemiology of the Disease or Condition

An anal fistula forms in 30-50% of cases as an outcome of acute paraproctitis [5-6].

The incidence of anal fistulas is 1.2-2.8 cases per 10,000 population per year. The disease most frequently develops at the age of 20 to 50 years, which accounts for its social significance. Men suffer from the disease 2-3 times more often than women [7-9].

1.4 Features of Coding the Disease or Condition

ICD-10 Codes

Chapter - Diseases of the digestive system (XI):

K60.3 Anal fistula

1.5 Classification of the disease or condition

Anal fistulas are classified as:

• complete (having both an internal and external fistula opening)

• incomplete internal (no external opening, only an internal one)

According to the localization of the internal opening in the anal canal:

• posterior (between 4 and 8 o'clock on the conventional clock face)

• anterior (between 10 and 2 o'clock on the conventional clock face)

• lateral (between 8 and 10 o'clock and between 2 and 4 o'clock on the conventional clock face)

Depending on the location of the fistulous tract relative to the external anal sphincter, they are distinguished as:

• intersphincteric

• transsphincteric

• extrasphincteric

Extrasphincteric fistulas are divided into 4 complexity grades:

• first grade of complexity: narrow internal opening, without scarring around it, no abscesses or infiltrates in the adipose tissue along the fistulous tract;

• second grade of complexity: scars are present in the area of the internal opening, but there are no inflammatory changes in the adipose tissue;

• third grade of complexity: narrow internal opening without scarring around it, but a purulent-inflammatory process is present in the adipose tissue;

• fourth grade of complexity: wide internal opening, surrounded by scars, with inflammatory infiltrates or purulent cavities in the tissues surrounding the fistula.

1.6 Clinical presentation of the disease or condition

The main clinical manifestations of an anal fistula include:

• presence of an internal fistula opening in the area of the anal crypt;

• presence of an external fistula opening on the skin of the perianal region, perineum, or gluteal region;

• serous, purulent, or serosanguineous discharge from the external fistula opening;

• recurrently occurring painful infiltrate in the perianal region or perineum, most often located in the area of the external fistula opening;

• discomfort and pain in the anal area.

With the exacerbation of a chronic purulent-inflammatory process in the pararectal adipose tissue, systemic inflammatory symptoms may appear, such as elevated body temperature and fever.

2. Diagnostics, medical indications and contraindications for diagnostic methods

application of diagnostic methods.

Criteria for establishing the diagnosis/condition - based on pathognomonic data:

1) clinical examination;

2) instrumental examination.

Diagnosis of an anal fistula involves several tasks:

1. determining the etiopathogenesis of the fistula;

2. localizing the internal and external fistula openings;

3. topographic and anatomical characteristics of the fistula (direction of its tract, location of the tract relative to the external sphincter, presence of tracking cavities);

4. assessing the severity and extent of the inflammatory process (presence of infiltrates, purulent cavities, involvement of adjacent organs);

5. assessing the function of the anal sphincter complex.

Differential diagnosis is performed to rule out inflammatory diseases of the skin and soft tissues that have no connection to the anal canal and rectum [10].

In addition, differential diagnosis is carried out:

• with inflammatory bowel diseases accompanied by perianal complications (Crohn's disease, ulcerative colitis);

• with fistulas of traumatic origin;

• with specific infections (tuberculosis, actinomycosis);

• with fistulas draining pelvic purulent cavities caused by other conditions (complicated tumors, perforated diverticulitis, etc.);

• with chronic inflammation of the pilonidal sinus;

• with fistulas draining caudal teratomas;

• with chronic osteomyelitis of the pelvic bones.

In pulmonary or intestinal tuberculosis, common cryptoglandular anal fistulas cannot be excluded. A specific process is suspected in cases where liquid pus is abundantly discharged from the fistulas, and histological examination reveals numerous coalescing granulomas with caseous necrosis. Very rarely, malignant transformation of an anal fistula occurs, in which case the discharge becomes bloody with an admixture of mucus. A reliable diagnostic method is cytological examination of fistula scrapings, preferably obtaining the scraping from the deep part of the tract rather than the area of the external opening [11].

Principles of formulation of diagnosis.

When formulating the diagnosis of an anal fistula, one should reflect the localization of the internal fistula opening (posterior, anterior, lateral), the location of the fistulous tract relative to the external anal sphincter (intersphincteric, transsphincteric, extrasphincteric), the presence or absence of an external fistula opening (complete or incomplete), as well as the presence or absence of cavities and tracking tracts along the course of the fistula and their localization. For extrasphincteric fistulas, the complexity grade of the fistula is additionally determined (see classification). Examples of diagnosis formulations are given below:

1. "Anterior intersphincteric anal fistula".

2. "Posterior transsphincteric anal fistula with an ischiorectal extension" (it is possible to indicate through which portion of the external sphincter the fistulous tract passes – subcutaneous, superficial, or deep portions).

3. "Lateral incomplete internal transsphincteric anal fistula".

4. "Posterior extrasphincteric anal fistula, grade 3 complexity" (it is possible to indicate the localization of perianal extensions – subcutaneous, ischioanal, retroanal, retrorectal, pelvirectal).

2.1 Complaints and Anamnesis

Characteristic complaints: serous, purulent, or serosanguineous discharge from the external fistula opening and/or anus, discomfort, pain in the anal area, presence of an inflammatory infiltrate in the soft tissues of the perianal region, perineum, or gluteal region.

The medical history may reveal: single or multiple surgical openings of acute paraproctitis, hypothermia, history of perianal trauma, pain in the anus and rectum, spontaneous rupture of a perianal abscess, and purulent discharge from the anus.

2.2 Physical Examination

• All patients with suspected anal fistula are strongly recommended to undergo a physical examination to confirm the diagnosis [1, 2, 6, 12, 13, 22]:

- inspection of the perianal region;

- digital rectal examination;

- probing of the fistula tract;

- dye test.

GCR ALEL 2Grade of Recommendation – A (Level of Evidence – 2)

Comment. Inspection of the perianal region aims to identify the external openings of the fistula, assess signs of inflammation, its severity and extent. The anal reflex is also checked.

During digital examination, attention should be paid to the internal opening of the fistula (localization, width and shape, presence of inflammation and scars), concomitant diseases of the anal canal and the lower ampullary rectum (hemorrhoids, anal fissure, neoplastic process, etc.).

Probing of the fistula tract is performed to assess the topographic and anatomical features of the fistula tract in relation to the anal sphincter complex (ASC) and the rectal wall, the direction of the tract, and the presence of cavities and fluid collections along the fistula. Probing is performed with a probe with a bulbous tip from the external opening for complete fistulas and from the internal opening for incomplete internal fistulas. Forceful probing of the fistula tract in the presence of obstacles should be avoided due to the risk of creating a false passage.

The dye test is performed to verify communication between the external opening of the fistula and the lumen of the anal canal, and to stain accessory fistula tracts and cavities. To perform the test, a gauze swab (marker) is inserted into the anus, then a dye (methylthioninium chloride or povidone-iodine** solution) is injected into the fistula tract through the external opening, after which the marker is carefully withdrawn from the anus without rotating it along its axis. A colored mark on the swab indicates a connection between the external and internal fistula openings. If the patient complains of discomfort or pain, the dye test should be stopped. The dye test has greater diagnostic value during surgery rather than at the stage of diagnosis establishment [2, 14].

It should be noted that the accuracy of physical examination in anal fistulas is lower than that of transrectal ultrasound of the rectum and magnetic resonance imaging of the pelvic organs [15].

2.3 Laboratory Diagnostics

Specific laboratory diagnostics for anal fistulas are currently unavailable. Laboratory diagnostic tests should be performed in patients during the preparation and planning of surgical intervention to rule out concomitant diseases and conditions.

2.4 Instrumental Diagnostics

Comment. Anoscopy is performed to accurately determine the location, assess the width and shape of the internal fistula opening, detect the presence or absence of scarring in the walls of the anal canal and rectum, and assess concomitant diseases of the anal canal [2, 6, 14].

• Colonoscopy is recommended for all patients over 40 years of age or those with suspected inflammatory bowel disease (IBD) to examine all parts of the colon and the terminal ileum [2, 6, 14].

GCP CLEL 5Grade of Recommendation – C (Level of Evidence – 5)

Comment. The examination is performed as an additional diagnostic method to assess the presence or absence of concomitant changes in the colon, inflammatory changes characteristic of Crohn's disease and ulcerative colitis, and to rule out colonic neoplasms in patients over 40 years of age [2, 6, 14].

• All patients with anal fistulas are recommended to undergo transrectal ultrasound of the rectum and anal canal and/or magnetic resonance imaging (MRI) of the pelvic organs to assess the position of the fistula tract relative to the anal sphincter, clarify the location of the internal fistula opening, diagnose purulent fluid collections, and identify additional fistula tracts. Both methods are comparable in diagnostic value [16-27].

GCR ALEL 1Grade of Recommendation — A (Level of Evidence — 1)

Comment. Transrectal ultrasound of the rectum and magnetic resonance imaging (MRI) of the pelvic organs are the methods of choice for topographic and anatomical assessment of the fistula tract.

Transrectal ultrasound of the rectum is relatively easy to perform, inexpensive, short in duration, and can be performed independently by either an ultrasound diagnostics physician or a coloproctologist. The study can also be supplemented by contrast enhancement of the fistula tract (usually a 3% hydrogen peroxide** solution diluted 1:1 with sodium chloride solution is used, which is injected through the external fistula opening) [28]. A disadvantage of the method is operator dependence. A simpler method for data interpretation in ultrasound is the use of a special probe that allows 3D image reconstruction. This expands visualization capabilities by providing images in all planes, similar to MRI. Pelvic MRI (examination with intravenous contrast is possible) demonstrates high detail and is an operator-independent study [29]. At the same time, MRI is an expensive study, requires the involvement of a radiologist, and takes more time.

Both methods have similar sensitivity and specificity in the diagnosis of anal fistulas [30, 31].

• In preparation for surgical intervention, patients with pre-existing anal sphincter dysfunction, those previously operated on for anal fistulas, patients scheduled for surgery for a transsphincteric fistula involving more than 30% of the sphincter, as well as those with extrasphincteric fistulas, are recommended to undergo an examination of the function of the rectal sphincter apparatus to detect incontinence, including subclinical forms [32].

GIB CLOE 4Grade of Recommendation – C (Level of Evidence – 4)

• Fistulography is not recommended for patient evaluation due to its low sensitivity and specificity [16].

GGR CLEL 3Grade of Recommendation – C (Level of Evidence – 3)

• Pelvic computed tomography in men and women is not recommended for patient evaluation due to its low sensitivity and specificity [16].

強B (level of recommendation — B)УДД 3Level of Recommendation — B (Level of Evidence — 3)

2.5 Other Procedures

Additional instrumental and laboratory examinations are performed for differential diagnosis.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

3.1 General principles of anal fistula treatment

The main treatment method for anal fistulas is surgical [2, 6].

Spontaneous healing of a fistula is extremely rare. Conservative treatment is not an independent method and is used in the perioperative period to reduce the severity and extent of the inflammatory process in the area of the fistula tract.

The choice of surgical treatment method is determined by a number of factors:

- the location of the fistula tract relative to the external sphincter;

- the severity and extent of the inflammatory process;

- the presence of additional fistula tracts, fluid collections, and cavities;

- the location and size of the internal fistula opening;

- the severity and extent of scarring in the walls of the anal canal and rectum in the area of the internal fistula opening;

- the condition of the ASC and the function of fecal continence [33, 34].

The goal of surgical intervention is the elimination of the fistula tract with maximum preservation of ASC structures and continence function. The choice of the optimal surgical method is determined by balancing the risk of anal fistula recurrence against the risk of anal incontinence. Maximum preservation of the structural elements of the ASC largely determines the functional outcome of treatment [2, 5, 6].

When deciding on the feasibility of using a particular method, the patient must be informed about the advantages and disadvantages of each intervention option in order to choose the most appropriate one for a specific clinical situation.

Contraindications to surgical treatment: severe decompensated comorbidities. If the patient's condition can be improved through prior treatment, surgery becomes possible.

The timeframe for radical surgery is determined mainly by the clinical course of the disease. Most patients undergo elective surgical treatment. In case of an exacerbation of chronic paraproctitis with abscess formation, surgery is performed on an emergency basis, similar to acute paraproctitis. It is inadvisable to postpone radical treatment for long, because the exacerbation may recur, and the inflammatory process followed by scarring of the anal canal wall, sphincter, and pararectal tissue can lead to deformation of the anal canal and perineum, and the development of anal sphincter deficiency [2, 5, 35].

3.2 Treatment of intersphincteric and transsphincteric fistulas involving less than 30% of the external sphincter

Fistulotomy or fistulectomy into the intestinal lumen

Comment. Fistulectomy into the intestinal lumen is performed as follows: the fistulous tract is laid open or excised into the intestinal lumen over a probe. The wound is left open or the wound edges are sutured to the wound base.

When comparing fistulectomy into the intestinal lumen and fistulotomy into the intestinal lumen, it was found that wound healing takes longer after fistulectomy, postoperative wounds are larger, and the risk of anal sphincter deficiency is higher. The recurrence rate of the disease does not differ statistically significantly between the two approaches. The average wound healing time is 6 weeks [40, 41].

To date, there is no consensus on how much muscle tissue can be divided during surgery for anal fistulas. The efficacy of fistulotomy or fistulectomy into the intestinal lumen is quite high, ranging from 92 to 97% [36, 37].

Impaired continence after fistulectomy into the intestinal lumen ranges from 0 to 45% [32-49]. The wide variation in data is due to different approaches to assessing anal sphincter function and the duration of postoperative follow-up. Risk factors for anal incontinence after fistulotomy or fistulectomy into the intestinal lumen include: preoperative signs of anal sphincter deficiency, recurrent fistula, female gender, fistulas involving more than 30% of the external sphincter, and a history of surgery for diseases of the anus, rectum, pelvis, and perineum [32, 38-40].

• Suturing the wound edges to the base after transsphincteric fistulectomy may be recommended to accelerate wound healing (average healing time is 5 weeks) [41, 49, 50].

GCR ALEL 2Grade of Recommendation – A (Level of Evidence – 2)

Treatment by fibrin glue injection into the fistulous tract

Comment. Fibrin glue injection is performed under anesthesia after debriding the fistulous tract to remove epithelial elements and necrotic tissue (using a Volkmann spoon, electrocautery, etc.). A thin, flexible tube is inserted through the external opening of the fistula up to the internal opening under digital control. Fibrin glue is injected using a syringe. While continuously injecting the glue, the tube is gradually withdrawn from the external opening, thereby filling the entire fistulous tract.

The efficacy of the described method in this category of patients is 26-78% [51-60, 108]. The efficacy rate is significantly lower than that of fistulectomy into the intestinal lumen, but the use of fibrin glue has several advantages: simple surgical technique, minimally invasive nature, no damaging effect on the anal sphincter complex, and significantly shorter postoperative rehabilitation periods. If a fistula recurs, the method of fibrin glue injection does not preclude its repeated use and does not create unfavorable conditions for more effective methods.

Treatment of fistulas using bioplastic material (bioplastic sealing plugs, bioplastic implants)

Comment. Bioplastic implants are recommended for patients with a fistulous tract length of at least 3 cm, in the absence of fluid collections. In preparation for treating fistulas with bioplastic sealing plugs, it is advisable to drain the fistulous tract using a seton for 4-8 weeks.

Sealing plugs made of bioplastic material and bioplastic collagen implants (porcine small intestinal submucosa, porcine dermal extracellular matrix and collagen, biocompatible synthetic materials such as polyglycolic acid) are used. The biological or biocompatible material from which the implant is made serves as a scaffold for the obliteration of the fistulous tract [61, 62].

The method is performed as follows: after debriding the fistulous tract with a Volkmann spoon to maximize the removal of necrotic tissue and granulation tissue, a bioplastic sealing material in the form of a cone-shaped plug is inserted into the fistulous tract, completely filling it. The distal end of the plug is brought out through the external opening. The widened part of the sealing plug, located in the area of the internal opening, is sutured with a few stitches to the edges of the mucosa from the side of the anal canal and rectal lumen for more secure fixation. According to literature data, the technique is effective in 50-70% of cases in patients with fistulas involving less than 1/3 of the external sphincter [61-65].

Fistulectomy with sphincter repair

Comment. This method involves the excision of a transsphincteric fistula with division of the portion of the sphincter through which the fistula passes, followed by suturing the ends of the divided muscle. The efficacy of the method reaches 97-100% [91-96].

3.3 Treatment of transsphincteric fistulas involving more than 30% of the sphincter and extrasphincteric fistulas

Fistulectomy with rectal mucosal advancement flap

Comment. The surgery is performed under anesthesia. The fistulous tract is excised from the external opening to the rectal wall. Next, 0.5-1 cm distal to the internal opening, a semilunar incision of the anal canal wall is made, encompassing about 1/4-1/3 of the circumference. The flap is mobilized proximally by sharp dissection for a distance of 2-4 cm. Depending on the specific technique, the rectal wall flap may be mucosubmucosal, mucosomuscular, or full-thickness. The internal opening is closed with 1-2 interrupted sutures, after which the flap is advanced distally and its edge is fixed without tension to the underlying muscle structures of the anal canal wall and/or perianal skin.

The rectal flap advancement procedure is sphincter-saving, as it does not damage the external sphincter. The efficacy of the method is 44-87% [76-85, 89].

The technique is not indicated in the presence of severe and extensive scar-inflammatory changes in the anal canal wall and lower ampulla of the rectum that hinder the mobilization and advancement of the flap [36, 77, 79-82].

Despite the fact that this method does not involve damage to the external anal sphincter, minor to moderate anal incontinence occurs in 7-38% of postoperative cases, as confirmed by postoperative anorectal manometry (decreased resting and voluntary squeeze anal canal pressure) [79, 83-85, 89]. This is explained by the fact that the mobilized flap typically includes elements of the internal sphincter, and the flap itself causes the rectal mucosa to shift into the anal canal, leading to moisture and mucus discharge.

To increase the efficacy of the technique in the presence of pronounced extensions, this surgery should be performed as a second stage after placing a draining seton for the period of inflammation remission.

Treatment of anal fistula using laser ablation of the fistula tract

Comment. Laser ablation is performed when a well-defined fistula tract is present or after placing a draining latex seton in the tract for 6-8 weeks, which facilitates the formation of a "straight" fistula with fibrous walls and significantly reduces the risk of persisting cavities and extensions along the tract. Laser ablation may be performed in the presence of superficial extensions with drainage through the external fistula opening.

The essence of the technique is laser coagulation of the fistula tract walls using a diode laser (wavelength 1470-1560 nm, radiation power 8–12 W) with a radial-emitting fiber optic probe.

The procedure is performed as follows: after cleaning the fistula tract with a small brush to maximally remove necrotic tissue and granulations, a diode laser fiber is inserted through the external opening along a guidewire and brought out through the internal fistula opening. As the fiber is gradually withdrawn at a speed of 1 mm/s, laser coagulation of the fistula walls is performed [69-72].

To ensure adequate drainage, the distal part of the fistula tract in the area of the external opening is excised. There are several options for completing the surgical intervention after laser ablation: without closure of the internal fistula opening, with closure of the internal fistula opening (using a Z-stitch or interrupted sutures), or with closure of the internal fistula opening using a mobilized mucosomuscular or advancement skin-anodermal flap.

The positive characteristics of this operation include: rapid patient rehabilitation, reduction of postoperative pain syndrome, and absent or minimal damaging impact on the anal sphincter complex, which prevents the development of anal incontinence. According to studies evaluating the efficacy of laser ablation, fistula healing ranges from 20 to 89% with a mean patient follow-up period of 7 to 48 months [69-75].

Treatment of fistulas using ligation of the intersphincteric fistula tract (LIFT)

Comment: The surgery is performed when a well-defined fistula tract is present or after prior placement of a draining latex seton in the tract for 6-8 weeks, which facilitates the formation of a "straight" fistula with fibrous walls and significantly reduces the risk of persisting cavities along the tract. Fundamentally, the method consists of ligating and dividing the portion of the fistula tract passing through the intersphincteric space [86-89]. A semilunar skin incision is made along the intersphincteric groove in the projection of the fistula tract. The fistula tract is identified in the intersphincteric space and mobilized circumferentially. At the borders of the external and internal sphincters, the fistula tract is divided and ligated, and the wound in the intersphincteric groove is closed. The distal part of the fistula tract in the area of the external opening is excised or the external opening is widened.

The LIFT operation has many modifications that do not fundamentally change the essence of the method. Wound healing occurs faster with this method than with rectal mucosal advancement flap surgery. Fistula healing occurs in an average of 76.5%, while incontinence phenomena develop significantly less frequently than after rectal advancement flap surgery with a comparable recurrence rate [86-89].

Fistulectomy with sphincter repair

• For patients with high recurrent transsphincteric and extrasphincteric fistulas, in the presence of cicatricial replacement of the sphincter in the area of the fistula, as well as when other sphincter-saving operations cannot be performed effectively and safely, excision of the transsphincteric and extrasphincteric anal fistula with sphincter repair is recommended [91-95].

Level of Evidence BGrade of Recommendation 3Level of Clinical Effectiveness – B (level of evidence – 3)

Comment. This method involves excision of the fistula tract (excision of the superficial or deep fistula tract) with division of the sphincter portion through which the fistula passes, followed by approximation of the ends of the divided sphincter muscle. The efficacy of the method ranges from 54 to 100%, averaging 93.2%, and is comparable to the efficacy of other surgical methods [91-95].

Impairment of anal continence function after surgery is observed in 4-32%. Dehiscence of the repaired sphincter edges or wound suppuration significantly increases the risk of anal incontinence, with the rate of suture dehiscence being higher in patients where the fistula passes through deeper parts of the external anal sphincter or is extrasphincteric [5, 92, 94].

Fistula excision with seton placement

• For patients with recurrent transsphincteric fistulas involving more than 1/3 of the external sphincter and extrasphincteric anal fistulas, in the presence of cicatricial replacement of the sphincter in the area of the fistula, when effective and safe sphincter-saving interventions or fistula excision with sphincter repair cannot be performed, and when the patient refuses repeated complex plastic procedures, excision of the fistula (excision of the deep fistula tract) with seton placement is recommended. A seton may be placed for draining the fistula tract and preventing purulent-inflammatory processes; in this case, its ends are not tightened, and the seton serves a draining function. A seton may also be placed for gradual staged division of the fistula tract and the tissues encompassed by the seton (cutting seton); in this case, it is tightened in stages at intervals of 1 time every 1-3 weeks [60, 97-106].

GSI ALoE 2Grade of Recommendation — A (Level of Evidence — 2)

Comments: The method of using a cutting seton in the treatment of anal fistulas is not sphincter-saving and is often performed when other methods are ineffective.

A seton (silk or latex) is passed through the fistula tract with the aim of gradually cutting through the fistula tract and sphincter fibers by periodically tightening the seton. Slow division of the sphincter muscle fibers by the seton prevents their retraction. Deterioration of continence function when using the seton method reaches up to 54% [97-103]. Literature data vary significantly in this regard [60, 103-106].

Treatment of fistulas by injection of fibrin glue and other bioplastic materials into the fistula tract

For patients with transsphincteric fistulas involving more than 1/3 of the external sphincter and extrasphincteric fistulas, these methods may be used due to their safety regarding the development of anal incontinence and low complication rate. Nevertheless, the fistula healing rate after applying these techniques does not exceed 50%, and the research results evaluating their efficacy are based on the use of methods in heterogeneous groups with a small number of patients with complex anal fistulas [107, 108].

GCR BLEL 2Grade of Recommendation – B (Level of Evidence – 2)

3.4 Treatment of anal fistulas associated with Crohn's disease (CD)

Comment. Perianal lesions in Crohn's disease (CD) occur in 40–80% of cases. Choosing the surgical treatment method for anal fistula in CD is challenging and requires an individualized approach. As a rule, the management of CD-related fistulas begins with conservative measures combined with therapy for the underlying disease. In 90% of cases, antibiotic therapy helps reduce the severity of perianal lesions [113, 114]. The use of infliximab** and other tumor necrosis factor-alpha (TNF-alpha) inhibitors promotes the healing of anal fistulas in an average of 46% of cases [111]. Despite favorable outcomes of conservative therapy for CD with perianal lesions, the choice of treatment for each patient is individualized and depends on the severity of the underlying disease and symptom severity. The treatment of choice for patients with high inflammatory activity in the perianal region, characterized by high, complex, multiple fistulas, destruction of the rectal sphincter structures during a CD flare-up, is permanent ostomy formation or surgery involving rectal extirpation, rectal resection, or abdominoanal resection with internal sphincter resection [112-116].

Comment. Anal fistulas in CD can be "secondary," i.e., associated with the underlying disease. Ulcerative defects with undermined edges located in the anal canal and rectum often mimic fistulas and may appear as fistulous tracts or fluid collections on imaging studies. Fistulas may also be associated with an inflammatory process in the cryptoglandular zone. Regardless of the fistula's etiology, if it is completely asymptomatic and there is no active inflammation, surgical treatment is not required [116, 117].

In such cases, the fistula may remain asymptomatic for a long period, but patients must be warned about the possibility of future surgery for the fistula.

Comment. Laying open or excising a superficial fistula into the intestinal lumen is a fairly safe and effective surgical intervention for intersphincteric fistulas and those involving the distal 1/3 of the external sphincter.

Considering the chronic course of the disease and the high probability of recurrence, maximum preservation of the rectal sphincter muscle structures is required during surgery. Therefore, several factors must be considered prior to surgery: the activity of the inflammatory process in the rectum, the functional state of the anal sphincter complex, previous rectal and perineal surgeries, and stool frequency and consistency.

With careful patient selection, favorable outcomes for this surgery are reported in 56-100% of cases. The incidence of moderately impaired fecal continence is 6-12% [113, 116, 119, 120].

• When treating anal fistulas in patients with transsphincteric fistulas involving more than 1/3 of the external sphincter and extra-sphincteric anal fistulas in the setting of CD, the first step recommended is the placement of a draining seton for 6 weeks or more to ensure adequate drainage of the abscess cavity (fluid collection) and prevent closure of the external opening [113-115].

GRC CLEL 4Level of Evidence Rating – C (Level of Evidence - 4)

Comment. Long-term use of a draining seton can significantly improve the outcomes of surgical repair for high transsphincteric and extrasphincteric fistulas. However, despite this intervention, approximately 20-40% of patients experience periodic flare-ups of the inflammatory process in the pararectal tissue [97, 121-123].

• As a second step, for patients with a transsphincteric fistula involving more than 1/3 of the external sphincter and an extrasphincteric anal fistula in the setting of CD, it is recommended to perform surgery aimed at eliminating the fistula (excising the transsphincteric and extrasphincteric fistulous tract), with the choice of surgical technique determined individually for each specific case. Any of the methods described above are acceptable [53, 71, 83, 84, 90, 125-128].

GIB CLOE 4Grade of Recommendation – C (Level of Evidence – 4)

Treatment of Crohn's disease-related anal fistulas using mesenchymal stem cells (MSCs).

Comment. Immediately before MSC administration, the draining seton is removed, and the solution containing mesenchymal stem cells is injected using a syringe along the fistulous tract, filling the space around it; the solution is also injected into the rectal wall in the area of the internal opening. If there are multiple fistulous tracts, the MSC administration procedure is repeated separately for each tract. The mechanism of action involves the anti-inflammatory, regenerative, and immunomodulatory properties of MSCs, as well as the stimulation of angiogenesis in the injection zone. Favorable outcomes after this technique with a follow-up period of more than 1 year range between 37 and 88% [125-128].

3.5 Anesthesia

In the event of acute or chronic pain syndrome, the patient is administered analgesia in accordance with existing pain management protocols (see relevant clinical guidelines on chronic pain), including opioid analgesics based on clinical indications.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

5. Prevention and Dispensary Observation

• All patients are recommended timely surgical treatment of acute paraproctitis with adequate drainage of the purulent cavity and subsequent monitoring of wound healing to prevent fistula formation [9, 14].

GCP CLEL 5Grade of Recommendation – C (Level of Evidence – 5)

Comment. Patients after incision and drainage of acute paraproctitis must have a clear understanding of the possibility of incomplete wound healing with subsequent fistula formation, or the potential for recurrence of the suppurative-inflammatory process in pararectal tissues, and recognize the importance of promptly notifying their physician of any clinical symptoms [9]. A potential measure for disease prevention is the timely treatment of concomitant anorectal disorders (hemorrhoids, anal fissure, cryptitis).

• Perioperative antibiotic therapy is advisable in cases of extensive inflammation, sepsis, immunodeficiency states and diseases, neutropenia, and IBD [129-131].

GCR ALEL 2Grade of Recommendation – A (Level of Evidence – 2)

Comment. Prevention of acute paraproctitis also involves general health-promoting measures aimed at eliminating the etiological factors of the disease. All patients are recommended:

- treatment and sanitation of foci of acute and chronic infection;

- management of chronic conditions such as diabetes mellitus and atherosclerosis;

- management of functional intestinal disorders;

- timely treatment of concomitant proctologic diseases.

6. Organization of Medical Care

• treatment of patients with anal fistulas may be carried out both on an outpatient basis and in a coloproctological inpatient setting;

• care for patients is provided by coloproctologists;

• prior to referring a patient for elective hospitalization, a full diagnostic workup must be performed to rule out risk factors and comorbidities;

• hospitalization of patients is carried out on a scheduled basis.

Indications for planned hospitalization:

• if there is a need to adjust treatment or if therapeutic measures cannot be performed in outpatient settings;

• inability to perform diagnostic or therapeutic procedures in an outpatient setting;

• failure of outpatient treatment;

• need for surgical treatment.

Indications for patient discharge:

• uncomplicated course of the early postoperative period;

• absence of purulent-septic complications;

• controlled pain syndrome with the possibility of management using oral medications in an outpatient setting;

• ability to achieve independent, full-fledged defecation;

• ability of the patient (for patients with limited mobility) to independently continue the course of conservative therapy in an outpatient setting under the supervision of an outpatient coloproctologist.

7. Additional Information

Negative factors affecting treatment outcomes include:

1. Development of infectious complications.

2. Bowel habit disorders (diarrhea or constipation).

3. Non-compliance by the patient with restrictions on physical activity and exertion.

Criteria for Evaluating the Quality of Medical Care

Quality assessment criteria for primary health care delivered to adults with anal fistula (ICD-10 codes: K60.3)

Quality assessment criteria for specialized medical care delivered to adults with anal fistula (ICD-10 codes: K60.3)

References

Appendix A1. Working Group Composition

All members of the working group are members of the Association of Coloproctologists of Russia.

There is no conflict of interest.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience of the clinical guidelines:

1. Coloproctologists

2. Surgeons

3. Gastroenterologists

4. General practitioners / Internists

5. General practitioners / Family physicians

6. Endoscopists

In these clinical guidelines, all data are ranked by level of reliability (evidence) depending on the quantity and quality of studies on the issue.

Table 1. Scale for grading levels of evidence (LE) for diagnostic methods (diagnostic interventions)

Table 2. Grading of levels of evidence (LE) for preventive, therapeutic, and rehabilitation methods (interventions)

Table 3. Grading of grades of recommendations (GR) for preventive, diagnostic, therapeutic, and rehabilitation methods (interventions)

Procedure for updating clinical guidelines

The clinical guideline update mechanism provides for systematic revision at least once every three years, as well as upon the emergence of new evidence-based data regarding the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or when justified additions/comments to previously approved clinical guidelines arise, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines were developed taking into account the following regulatory legal documents:

1. Clause 3 of Article 37 of Federal Law of the Russian Federation No. 323-FZ dated November 21, 2011, "On the Fundamentals of Healthcare Protection in the Russian Federation" (as amended and supplemented, effective January 11, 2023);

2. Order of the Ministry of Health of the Russian Federation No. 203n dated May 10, 2017, “On Approval of Criteria for Assessing the Quality of Medical Care”;

3. Order of the Ministry of Health of the Russian Federation No. 206n dated April 2, 2010 (as amended on February 21, 2020) "On Approval of the Procedure for Providing Medical Care to the Population with Colorectal Diseases, Diseases of the Anal Canal, and Perineum in Coloproctology";

4. Order of the Russian Ministry of Health No. 694n dated June 30, 2021, "On Approval of Standards of Medical Care for Adults with Anal Fistula" (including the "Standard of Medical Care for Adults with Anal Fistula (Diagnosis and Treatment)", "Standard of Medical Care for Adults with Anal Fistula (Dispensary Follow-up)").

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Disease Information. Anal fistula is a chronic inflammatory condition of the pararectal adipose tissue, characterized by the presence of an internal opening in the anal canal and a fistulous tract that may open onto the skin in the perianal region or adjacent areas (gluteal, inguinal, sacrococcygeal). The only definitive (radical) treatment for fistulas is surgery, during which the fistulous tract and internal opening are eliminated, and any purulent cavities are opened and drained. In the absence of timely surgical treatment, the condition is frequently complicated by exacerbations of the purulent-inflammatory process, which can lead to life-threatening sepsis or extensive purulent-necrotic melting of the soft tissues surrounding the rectum. These conditions require emergency hospitalization and surgical treatment and present a direct threat to the patient's life.

Information needed for the postoperative period. In the postoperative period, during the first 1–3 months after surgery, proper hygiene measures (sitz baths with chamomile decoction, washing with cool water) and regulation of stool frequency and consistency are crucial. It is necessary to achieve regular daily stools of a soft consistency that do not traumatize wound surfaces in the anal canal and perianal region.

If difficulty in defecation or constipation develops, normalization of stool consistency must be achieved. The treatment of constipation, unless caused by conditions requiring surgical intervention, should begin with a diet containing sufficient amounts of dietary fiber, fermented milk products, and vegetable oil. Smoked, salted, and pickled foods, cocoa, and chocolate should be excluded from the diet, while fried foods, sausage products, and rye bread should be partially limited. Try to include less bread and bakery products made from premium wheat flour (especially fresh and soft ones), pasta, and semolina dishes in your diet. Foods rich in fiber and ballast substances (found in plant-based foods, primarily grains) are recommended. Foods that contribute to stool normalization include: fresh kefir, prostokvasha (fermented baked milk/sour milk), and acidophilus milk. Prunes and figs soaked in water, their infusions, plum juice, boiled beets, and dried fruit puree have a positive effect. Soups, borscht, and cabbage soup made with a strong vegetable broth are beneficial as first courses.

Dietitians recommend carrot, prune, and apple puddings with lemon, beet puree, and vinaigrette salad with vegetable oil. It is recommended to drink a glass of mineral water, fruit juice (plum, peach, apricot), or a hot lemon drink on an empty stomach in the morning. Grated carrots, raw apples, prostokvasha, and 5–7 prunes washed and soaked in boiling water overnight have a laxative effect when eaten on an empty stomach. In addition, provided the general condition is satisfactory, walking and light physical activity are indicated. Morning gymnastics, physical exercises focusing on the abdominal muscles, and brisk walking are recommended.

Pharmacotherapy for constipation should be carried out with great caution, in short courses, under medical supervision.

Several additional recommendations for constipation:

1. Consult your physician to determine which of the above recommendations are suitable for you;

2. Drink 4–8 glasses of fluids per day;

3. Your diet should include foods that promote bowel motility. We recommend whole-grain bread, bran crispbreads, porridges—buckwheat, oatmeal, wheat, pearl barley with milk or vegetable oil, and grain dishes. Include fiber-rich foods in your diet (dietitians recommend adding raw vegetables, fruits, nuts, and sprouted wheat to milkshakes, for example). Try oatmeal cookies and cornflakes;

4. Apples, figs, dates, and tea with lemon help some patients considerably;

5. Prune decoction is beneficial in the mornings and at night;

6. Be sure to add bran to your food, starting with one teaspoon per day. Then, increase this amount to 4–6 tablespoons per day. Increasing the dose too quickly can cause loose stools and abdominal bloating. Try adding bran to porridges, rice or potato casseroles, and dairy products;

7. During antitumor drug therapy, use laxatives only as a last resort.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

No.