What Is Fistula-In-Ano?
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Fistula-In-Ano- Causes, Symptoms, and Treatment

Published on Jan 24, 2023   -  4 min read


The connecting tunnel between the perianal skin and anal canal is fistula-in-ano. Read the article below to know more about it.

What Is Fistula-In-Ano?

An epithelial-lined tract that connects the anal canal to the perianal skin is fistula-in-ano. These fistulas usually occur as a result of an anorectal abscess. It is a benign condition that can cause embarrassment and distress to patients. This often occurs following an anorectal abscess. When an anorectal abscess occurs, it obstructs the anal gland resulting in abscess formation and infection. Around 30 to 70 % of patients with an anorectal abscess will have a fistula on examination. Another one-third of the patient's fistula develops later to anorectal abscess drainage.

What Are the Causes of Fistula-In-Ano?

Many glands are present in the anus that secrete fluid. Sometimes these glands get blocked and clogged. Due to this, bacteria builds up and can create a swollen sac of infected tissue and liquid, resulting in an anal abscess. If timely treatment of the abscess is not done, it can puncture, and the fluid can drain out. In most cases, the abscess turns into a fistula, which is a tunnel that connects the gland to the opening. Other conditions that cause fistula are sexually transmitted diseases, tuberculosis, illness of bowel, ulcerative colitis, Crohn's disease, cancer, and chemotherapy.

Who Is at the Risk of Getting Fistula-In-Ano?

The risk factors of fistula-in-ano include:

  • Crohn’s disease.

  • Colitis.

  • Chronic diarrhea.

  • Chemotherapy treatment for rectal cancer.

What Are the Signs and Symptoms of Fistula-In-Ano?

The signs and symptoms of anal fistula include:

How Is Diagnosis Done for Fistula-In-Ano?

The diagnosis of anal fistula is done by taking a record of your medical history and the symptoms observed. During the physical examination, the healthcare provider will look for a fistula opening near the anal opening. Palpating the area to find any sore or oozing pus. Other methods used for diagnosis are:

  • Anoscope: A special scope used to examine inside the anal canal.

  • Fistula Probe: A long thin, flexible tube is used through the outer opening of the fistula, and a special dye is injected to find out the openings and endings of the fistula.

  • CT Scan: Imaging technique used to create images of the anal area using computer technology and soundwaves.

  • MRI (Magnetic Resonance Imaging): Images the area with the help of special magnets and computer technology.

What Is the Treatment Provided for Fistula-In-Ano?

Fistula-in-ano is not only treated with medical interventions like antibiotic therapy but surgical intervention is also required. The surgical treatment includes:

  • Fistulotomy: It is usually an outpatient procedure. A procedure that opens up the fistula and heals the fistula inside out.

  • Reconstructive Surgery: Surgeries are done in stages. In some cases, this may be the option.

  • Seton Placements: This procedure includes placing a rubber band (seton) or suture in the fistula that tightens slowly. It lets the fistula drain and heal from behind the seton placement. This procedure lowers the risk of incontinence.

  • Filling the Fistula With a Special Plug or Glue: This is a new treatment that closes the inner opening of the fistula. The fistula tunnel is filled with absorbable material that the body absorbs over time.

Often anal fistulas are associated with Crohn’s disease. Fistula surgeries are usually done on an outpatient basis, but deep fistula cases require hospitalization. Even some fistulas require several recurrent surgeries to get rid of the fistula.

What Is Seton?

Setons are temporary initial interventions in the management of the fistula. It is a non-absorbable, nylon, silk suture that is guided in the fistula tract, and then it is tied this way exteriorly, and the compressing and maintaining of suture placement is done. For seton placement, a small vessel loop is used. This placement of seton is left for prolonged periods from weeks to months. Setons are used in individuals with a risk of secondary inflammation or inflammatory bowel disease association. Setons allow epithelization of the tract of the fistula and thus preventing secondary closure and also facilitating abscess drainage.

What Is the Differential Diagnosis of Fistula-In-Ano?

Differential diagnosis of fistula-in-ano is:

  • Constipation - A condition in which stool passing becomes difficult.

  • Diverticulitis- A condition in which small bulging pouches form on the lining of the digestive tract resulting in inflammation and infection.

  • Anorectal Abscess- A condition that is usually caused by blocked glands and anal infections.

  • Pilonidal Cyst- A condition in which abnormal skin growth occurs in the sacral region that contains skin and hair.

  • Hidradenitis Suppurativa- A chronic condition of the skin that is characterized by lumps in the armpits and groin.

  • Acute Proctitis- A condition in which the inflammation of the lining of the rectum, the rectal mucosa.

  • Inflammatory Bowel Disease- Inflammatory bowel disease is a combination of digestive disorders like Crohn’s disease or ulcerative colitis.

  • Anal Carcinoma- A condition in which cancer cells form over the tissue of the anus. Most cases are related to human papillomavirus.

  • Pilonidal Sinus- When a pilonidal cyst gets infected and forms into an abscess. Over time it ruptures, and the pus starts draining into the sinus, known as a pilonidal sinus.

What Are the Complications of Surgery in Fistula-In-Ano?

Complications of fistula-in-ano come after the treatment. An inability to control bowel movements is fecal incontinence. This occurs due to the removal of muscle around the anal opening, and the sphincter is removed in the surgery. Recurrence of anal fistula is higher in smokers, obese patients, and with a history of anal surgery. Recurrence occurs within one year of treatment.


Fistula-in-ano is not a life-threatening condition but can significantly impact the life of an individual. Fistulas respond well to surgery. After the surgery, a warm bath for the affected areas is recommended, known as a sitz bath. Also, stool softeners and laxatives are recommended for a week or more. For prolonged pain after surgery, the healthcare provider injects Lidocaine at the site to decrease the pain and discomfort, and also painkillers are prescribed.

Last reviewed at:
24 Jan 2023  -  4 min read




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