Anal fistula

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

The anal fistula is an abnormal connection between the anorectal canal and the perianal skin that is lined with granulation tissue. Anal fistula develops from infection of anal crypts gland. Anal fistulas are classified depending upon the location of sphincter into 4 types-intersphincteric, transsphincteric, suprasphincteric, extrasphincteric. Anal fistula are classified into two categories based on the risk factors associated- simple anal fistula and complex anal fistula. Anal fistulas are also classified according to primary tracks into two- high and low anal fistulas. Anal fistulas patient presents with rectal pain, discharge. On rectal examination, there is redness, tenderness and discharge are seen. The anal fistula is diagnosed clinically and endoanal ultrasonography and MRI helps in finding out the anatomy of fistula. The mainstay of treatment is surgery but medical therapy for symptomatic relief of pain and fever. Antibiotics are used if there are sepsis and treatment of underlying cause is very important to prevent recurrence of fistula. Various options for surgical management are fistulotomy and Seton. Sphincter-saving methods are fibrin glue, endorectal advancement flap, LIFT procedure, BioLIFT, stem cells and defunctioning.

In 1880, Herman and Desfosses described the anal glands within the internal sphincter, sub-mucosa and their opening into the anal crypts and demonstrated that the infection of these glands and the spread of the infection through the intersphincteric space can result in the formation of an anorectal abscess. In 1900, Goodsall found a rule of thumb that uses the location of fistula for the treatment of fistula.

Anal fistula are classified into four types based on the relationship to sphincter– intersphincteric, transsphincteric, suprasphincteric, extrasphincteric. Anal fistula are classified into two categories based on the risk factors associated- simple anal fistula and complex anal fistula. Anal fistulas are also classified according to primary tracks into two- high and low anal fistulas.

Anal fistula develops from infection of anal crypts gland. The initial infection occurs in the ducts of the anal glands and the spread of infection results in the formation of the abscess.If the abscess is ruptured, a fistula is formed. Anal fistulas are associated with following conditions are diverticulitis, foreign-body reactions actinomycosis, chlamydia, lymphogranuloma venereum (LGV), syphilis, tuberculosis, radiation exposure, HIV disease, Crohn’s disease, pilonidal disease, hidradenitis suppurativa, trauma, previous surgery (including ileoanal pouch surgery), presacral dermoid cysts, sacrococcygeal teratoma.

Anal fistula is caused by crohn’s disease, obstetric injury, retained foriegn body in rectum, radiation proctitis, gonorrhea, HIV, cryptitis, lymphogranuloma venereum, perirectal abscess sequel of rupture or surgery, syphilis, thrombosed hemorrhoids, tuberculosis, ulcerative colitis.

Anal fistula must be differentiated from other causes of anal pain including anal fissure, thrombosed hemorrhoids, levator spasm, sexually transmitted disease, proctitis, hidradenitis suppurativa, infected skin furuncles, herpes simplex virus, tuberculosis, syphilis, actinomycosis and cancer.

The prevalence of anal fistula is approximately 1-2 per 10,000 individuals worldwide. In England, the incidence of anal fistula is approximately 18.4 per 10,0000 per year. Anal fistula commonly affects individuals in the third, fourth, and fifth decades, with a peak around 40 years of age. Men are twice more commonly affected by anal fistula than women.

Common risk factor in the development of anal fistula are diabetes, smoking, alcohol, obesity.

According to The American Society of Colon and Rectal Surgeons, screening for the anal fistula is not recommended.

Anal fistula usually develops in 20-30 years of age and peaks around 40 years. If left untreated, patients with anal fistula may progress to develop the perianal abscess and cancer. Common complications of anal fistula include: urinary retention, bleeding, perianal abscess, fecal incontinence, carcinoma. Prognosis is excellent after surgery and recurrence rate is 7-2.

There is no diagnostic criteria associated with anal fistula.

The hallmark of anal fistula is rectal pain during defecation, sitting and cough. A positive history of Crohns disease, Rectal abscess, Obstetric injury and prior anorectal injury is suggestive of anal fistula. Common symptoms are intermittent rectal pain during defecation, sitting and any activity, pain is throbbing in quality and sometimes occur throughout the day and resolved by opening the track, recurrent perianal malodourous discharge, perianal bloody discharge, perianal pruritis. Less common symptoms of anal fistula are fever and pain referred to thighs, low back, or buttocks.

Patients with anal fistula usually appear in distress due to throbbing rectal pain. Patient presents with anal fistula is having normal vital signs but if anal fistula gets infected, it will lead to the formation of an abscess. Patient with an abscess presents with unstable vitals like High-grade fever, tachycardia, tachypnea, low blood pressure. On rectal examination, there is redness, tenderness and discharge is seen.

There are no diagnostic laboratory findings associated with anal fistula. The anal fistula is mostly diagnosed clinically but in case of complication like the anal abscess, tests done are – complete blood count with differentials, blood culture, ESR, wound culture.

Fistulography is used to diagnose anal fistula in the past but is replaced by MRI nowadays. This is used to find out the anatomy of fistulas.

There are no CT scan findings associated with anal fistula.

MRI is the gold standard imaging study to know about fistula anatomy. Indications are recurrent fistulas and complex fistulas.

There are no ECG associated with anal fistula.

Endoanal ultrasound used to know details of fistula anatomy, tracks, and the sphincters. This is used intraoperatively by surgeons to have better information of fistula. Accuracy of endoanal ultrasound is improved by injection of hydrogen peroxide into fistula tracks. Ultrasound has a limited use because probe can go 2 cm from the anus so it is poor at evaluating pathology beyond the sphincters.

Anoscope is used to visualize the internal opening of fistula. Sigmoidoscopy is used to visualize the opening of fistula in the rectum.

There are no other diagnostic studies associated with anal fistula.

Pharmacotherapy used in anal fistula depends upon the location and symptoms of patient. Antibiotics are used in patient with comorbities like immunosuppression, diabetes, extensive cellulitis, prosthetic devices and high risk cardiac patients. Antipyretics and analgesic for symptomatic relief of pain and fever. Treatment of underlying causes is important to treat recurrent anal fistulas.

The mainstay of treatment of anal fistula is surgical treatment.The principles for the management of anal fistula are described by the acronym SNAP, which stands for sepsis, nutrition, anatomy, and procedure according to British Medical Journal. Various methods of surgery are Fistulotomy and Seton. Sphincter-saving methods are Fibrin glue, endorectal advancement flap, LIFT procedure, BioLIFT, Stem cells and defunctioning.

Adequate treatment of crohn’s disease, HIV infection, actinomycosis, cryptitis, gonorrhea, syphilis, tuberculosis, and ulcerative Colitis. Maintaining proper hygiene.

Proper treatment of the anal fistula will prevent the complications, such as perianal abscess and cancer.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

In 1880, Herman and Desfosses described the anal glands within the internal sphincter, sub-mucosa and their opening into the anal crypts and demonstrated that the infection of these glands and the spread of the infection through the intersphincteric space can result in the formation of a anorectal abscess. In 1900, Goodsall found a rule of thumb that uses the location of fistula for the treatment of fistula.

• In 1880, Herman and Desfosses described the anal glands within the internal sphincter, sub-mucosa and their opening into the anal crypts and demonstrated that the infection of these glands and the spread of the infection through the intersphincteric space can result in the formation of a anorectal abscess.
• Tucker and Hellwig, provided evidence that the initial infection occurs in the anal ducts allowing the infection to spread from the anal lumen into the anal canal wall.^[1]
• In 1900, Goodsall found a rule of thumb that uses the location of fistula for the treatment of fistula.^[2][3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Anal fistula are classified into four types based on the relationship to sphincter– intersphincteric, transsphincteric, suprasphincteric, extrasphincteric. Anal fistula are classified into two categories based on the risk factors associated- simple anal fistula and complex anal fistula. Anal fistulas are also classified according to primary tracks into two- high and low anal fistulas.

Anal fistulas are classified into the four types based on the relationship to sphincter:^[1][2]

• Intersphincteric
• Transsphincteric
• Suprasphincteric
• Extrasphincteric

Anal fistulas are classified into two categories based on the risk factors associated:

• Simple anal fistula:^[3]
  • There are no risk factors associated with simple anal fistula.
  • Treatment of simple anal fistula results in low incidence of fecal incontinence and poor wound healing.
• Complex anal fistula:^[4]
  • There are many risk factors associated with complex anal fistula e.g preexisting incontinence, recurrent fistula, local irradiation, chronic diarrhea, or crohn’s disease.
  • There are multiple tracts found in complex anal fistula and is anterior in the location in females.

Anal fistulas are classified according to the position of primary tracks:^[5]

• Low fistula – In a low fistula close to the skin and the track passes through few or no sphincter muscle fibres.
• High fistulas– High fistula passes through multiple muscle fibers.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Anal fistula develops from infection of anal crypts gland. The initial infection occurs in the ducts of the anal glands and the spread of infection results in the formation of the abscess.If the abscess is ruptured, a fistula is formed. Anal fistulas are associated with following conditions are diverticulitis, foreign-body reactions actinomycosis, chlamydia, lymphogranuloma venereum (LGV), syphilis, tuberculosis, radiation exposure, HIV disease, Crohn’s disease, pilonidal disease, hidradenitis suppurativa, trauma, previous surgery (including ileoanal pouch surgery), presacral dermoid cysts, sacrococcygeal teratoma.

• The anal canal is a 2 to 4cm in length, starts at the anorectal junction to the end of anal verge.^[1]
• It is divided into an upper and a lower part by transition zone that is seen at the dentate line or pectinate line which is surrounded by longitudinal mucosal folds, called columns of Morgagni.^[1]
• Each of this fold contains anal crypts, each of which contains 3 to 12 anal glands, the distribution of these glands is not uniform with most of the glands present anterior to the position of the anal canal and fewer in the posterior position.

There are following steps in the formation of anal fistula:

• Anal fistula develops from infection of anal crypts gland.

• The initial infection occurs in the ducts of the anal glands and the spread of infection results in the formation of the abscess.^[2]
• The crytoglandular theory states that obstruction of anal gland duct results in a infection.
• The presence of these glands deep in relation to the anal canal and sphincter, the infection follows the path of least resistance resulting in abscess formation at the termination of the gland.^[3][4]

• If the abscess is ruptured, a fistula is formed.

Anal fistulas are associated with following conditions:^[5]

• Diverticulitis
• Foreign-body reactions
• Actinomycosis
• Chlamydia
• Lymphogranuloma venereum (LGV)
• Syphilis
• Tuberculosis
• Radiation exposure
• HIV disease
• Crohn’s disease
• Pilonidal disease
• Hidradenitis suppurativa
• Trauma
• Previous surgery (including ileoanal pouch surgery)
• Presacral dermoid cysts
• Sacrococcygeal teratoma
• Rectal duplication

On gross pathology:

• They are seen linear or completely maloriented and have the epithelial lining at one of its edges.

On microscopic histopathological analysis, following features are found:^[6]

• There is the central core of active and chronic inflammation with granulation tissue, foreign body giant cells, and surrounded by scar.
• Granulomas are seen occasionally.
• There is squamous cell extend into the fistula track which is partially epithelialized.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Anal fistula is caused by crohn’s Disease, obstetric injury, retained foriegn body in rectum, radiation proctitis, gonorrhea, HIV, cryptitis, lymphogranuloma venerum, perirectal abscess sequelae of rupture or surgery, syphilis, thrombosed hemorrhoids, tuberculosis, ulcerative Colitis.

Anal fistula is caused by:^{[1][2][3][4][5][6]}

• Crohn’s Disease
• Obstetric injury
• Retained foriegn body in rectum
• Radiation proctitis
• Gonorrhea
• HIV
• Cryptitis
• Lymphogranuloma venereum
• Perirectal abscess sequel of rupture or surgery
• Syphilis
• Thrombosed hemorrhoids
• Tuberculosis
• Ulcerative Colitis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Anal fistula must be differentiated from other causes of anal pain including anal fissure, thrombosed hemorrhoids, levator spasm, sexually transmitted disease, proctitis, hidradenitis suppurativa, infected skin furuncles, herpes simplex virus, tuberculosis, syphilis, actinomycosis and cancer.

Anal fistula must be differentiated from other causes of anal pain, including anal fissure, thrombosed hemorrhoids, levator spasm, sexually transmitted disease, proctitis, hidradenitis suppurativa, infected skin furuncles, herpes simplex virus, tuberculosis, syphilis, actinomycosis and cancer.^[1]

Disease	Definition	Causes	Clinical Features	Diagnosis
Anal fistula	A epithelialized track formed between the anorectum and the perianal skin secondary to rupture of anorectal abscess Chronic manifestation of anorectal abscess	Anorectal abscess Crohn’s Disease Radiation proctitis Lymphogranuloma venereum Actinomycosis	Anal pain with bowel movement and sitting Perianal discharge Perianal pruritus Presence of exteral opening on examination Perianal inflammation	Endoanal ultrasound Fistulography Computed tomography
Anal Fissure	Tear in the anoderm distal to the dentate line	Anal Trauma Receptive anal sex Inflammatory bowel disease	Pain with passing of stools Minimal bright red rectal bleeding on the toilet paper or stool On examination acute fissure appears as a fresh laceration Chronic fissure has raised edges with anal skin tag	Clinical diagnosis
Thrombosed external hemorrhoids	Engorged fibrovascular cushions lining the anal canal	Constipation Prolonged straining	Anal pain Anal pruritus Rectal bleeding with bowel movement Tenderness on examination with a palpable thrombus	Clinical diagnosis
Levator spasm	Severe, intermittent episodes of rectal pain	Seen in patients with perfectionistic, anxious somatic, and/or neurotic tendencies	Severe anal pain lasting for seconds to 5 minutes	Diagnosis is by Rome IV criteria It is diagnosis of exlusion
Proctitis	Epithelial damage to the rectum secondary to radiation, associated with minimal or no inflammation	Radiation therapy	Diarrhea within six weeks of radiation therapy Urgency Tenesmus Rectal bleeding	Biopsy
Hidradenitis suppurativa	Suppurative disorder of sweat glands	Causes unidentified	Anal pain Anal mass Recurrent and relapsing symptoms Nodules and scarring is demonstrated on examination	Clinical Diagnosis Biopsy should be done to rule out cancer
Infected skin furuncle	Well-circumscribed, painful, suppurative inflammatory nodule involving hair follicles	Staphylococcus aureus	Anal pain Inflammed and red, tender elevated pustular lesion on examination	Clinical diagnosis
Bartholin’s abscess	Obstruction of the bartholin’s ducts, results in abscess formation	E.coli	Vulvar pain Palpable bartholin gland on examination	Clinical diagnosis Incision and drainage

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

The prevalence of anal fistula is approximately 1-2 per 10,000 individuals worldwide. In England, the incidence of anal fistula is approximately 18.4 per 10,0000 per year. Anal fistula commonly affects individuals in the third, fourth, and fifth decades, with a peak around 40 years of age. Men are twice more commonly affected by anal fistula than women.

• The prevalence of anal fistula is approximately 1-2 per 10,000 individuals worldwide.
• In Spain, the prevalence of anal fistula is approximately 1.04 per 10,000 per year.
• In Italy, the prevalence of anal fistula is approximately 2.32 per 10,000 per year.^[1][2][3]

• In England, the incidence of anal fistula is approximately 18.4 per 10,0000 per year.

Anal fistula commonly affects individuals in the third, fourth, and fifth decades, with a peak around 40 years of age.^[4]

Men are twice more commonly affected by anal fistula than women.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Common risk factor in the development of anal fistula are diabetes, smoking, alcohol, obesity.

• Common risk factors in the development of anal fistula include:^[1][2][3]
  • Diabetes
  • Smoking
  • Alcohol
  • Obesity

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

According to The American Society of Colon and Rectal Surgeons, screening for the anal fistula is not recommended.

According to The American Society of Colon and Rectal Surgeons, screening for the anal fistula is not recommended.

Template:WS Template:WH

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Anal fistula usually develops in 20-30 years of age and peaks around 40 years. If left untreated, patients with anal fistula may progress to develop the perianal abscess and cancer. Common complications of anal fistula include: urinary retention, bleeding, perianal abscess, fecal incontinence, carcinoma. Prognosis is excellent after surgery and recurrence rate is 7-21%.

• The symptoms of anal fistula usually develop in the second and third decade of life and peaks around 40 years.
• If left untreated, patients with anal fistula may progress to develop the perianal abscess and cancer.

Common complications of anal fistula include:

• Urinary retention
• Bleeding
• Perianal abscess
• Fecal incontinence
• Carcinoma

• Prognosis is excellent after the surgery.
• Recurrence rate is 7-21% depending upon the anatomy and complexity of fistula.^[1][2]

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