About Anal Fistula

A fistula is an abnormal tunnel-like connection between two epithelial-lined surfaces that do not usually connect. In most cases, it forms due to an infection, injury, inflammation, or surgery that causes an unnatural communication between organs or tissues. Anal fistula is the most common type, usually developing between the anal canal and the perianal skin, often following an untreated or recurrent anal abscess. 

Fistulas can also occur in other regions—such as rectovaginal, enterocutaneous, or vesicovaginal fistulas—depending on the anatomical involvement. Left untreated, fistulas can cause persistent infection, pain, discharge, and in rare cases, lead to more serious complications like sepsis or fecal incontinence.

Anal Fistula Signs & Symptoms

The symptoms of a fistula can vary depending on its type and severity. Common signs include:

• Chronic discharge: Pus or stool leaking through the external opening near the anus or other abnormal sites.
• Pain or irritation: Especially during bowel movements or prolonged sitting.
• Redness or swelling: Around the external opening or tract site.
• Foul-smelling drainage: From the perianal area, sometimes associated with bleeding.
• Recurrent abscesses: Suggest an underlying fistula tract if the abscess keeps returning.
• Systemic symptoms: Fever, fatigue, or malaise may accompany severe infections or deeper fistulas.

Anal Fistula Causes

Fistulas may develop due to a variety of causes depending on the location and underlying disease. Common etiologies include:

• Perianal abscess: A major precursor to anal fistulas; when pus from the abscess finds a path to escape, it creates a tract.
• Crohn’s disease: Chronic inflammatory bowel disease that weakens intestinal walls, allowing abnormal tract formation.
• Surgical trauma: Pelvic or abdominal surgeries can lead to fistula formation due to injury or poor wound healing.
• Infections: Tuberculosis, HIV, or other chronic infections may cause caseating necrosis and tissue breakdown.
• Radiation therapy: Can damage tissues and contribute to the development of post-radiation fistulas, especially in cancer patients.
• Obstetric trauma: Difficult vaginal deliveries or episiotomy complications can cause rectovaginal fistulas.

Anal Fistula Risk Factors

Several factors can increase the likelihood of developing a fistula, particularly around the anal or rectal region:

• Chronic Anal Abscesses: Recurrent or untreated abscesses are one of the leading risk factors, as they can form persistent tracts to the skin.
• Inflammatory Bowel Disease (IBD): Conditions like Crohn’s disease significantly raise the risk due to chronic intestinal inflammation and ulceration.
• Previous Anorectal Surgery: Surgical interventions in the rectal or perianal region can sometimes lead to fistula formation as a postoperative complication.
• Trauma or Injury: Direct injury to the anorectal area, whether from childbirth, pelvic trauma, or medical procedures, can contribute to fistula development.
• Infections (Tuberculosis, HIV, STIs): Certain infections, especially in immunocompromised individuals, may cause chronic inflammation and tissue breakdown, leading to fistulas.

Complications of Anal Fistula

If not treated properly, fistulas can lead to serious health issues:

• Recurrent infections or abscesses: Due to persistent drainage or blockage of the tract.
• Fecal incontinence: Can occur if the sphincter muscles are damaged during surgery or due to disease progression.
• Sepsis: Rare but life-threatening infection in case of widespread tract infection.
• Malignancy: Long-standing fistulas, especially in Crohn’s patients, may carry a rare risk of cancerous transformation.
• Delayed healing or recurrence: Especially with complex fistulas or inadequate primary treatment.
   

Anal Fistula Diagnosis

Accurate diagnosis is crucial for effective fistula management. Diagnostic steps typically include:

• Physical examination: Inspection and gentle probing to locate the external opening and define the tract.
• Digital rectal exam (DRE): To assess internal opening and nearby induration or tenderness.
• Proctoscopy or anoscopy: Visualization of the internal opening of the fistula from inside the rectum.
• MRI Pelvis (Fistula protocol): Gold standard imaging for complex or high anal fistulas, giving detailed tract anatomy.
• Endoanal ultrasound (EAUS): Helpful in evaluating the sphincter complex and guiding surgical planning.
• Fistulogram: X-ray imaging after injecting dye into the external opening (less commonly used now).
• CT scan: For fistulas associated with abdominal disease or intra-abdominal abscess.

Anal Fistula Treatment

The treatment of fistula primarily depends on its complexity, tract anatomy, and involvement of surrounding structures such as the anal sphincters. Most require surgical management.

• Fistulotomy: Simple fistulas are laid open surgically to allow healing from the base; effective for low transsphincteric tracts.
• Seton placement: A thread or silicone loop is placed to promote drainage and fibrous healing while preserving sphincter function; useful in high or complex fistulas.
• LIFT (Ligation of Intersphincteric Fistula Tract): A sphincter-sparing technique where the internal opening is ligated and the tract is excised.
• Advancement flap: A flap of rectal or vaginal tissue is used to cover the internal opening, particularly in recurrent or high fistulas.
• VAAFT (Video-Assisted Anal Fistula Treatment): Minimally invasive, uses a fistuloscope to visualize and ablate the tract internally.
• FiLaC (Fistula Laser Closure): A laser probe destroys the tract lining; quick recovery with minimal sphincter damage.
• Biological plug or glue: Collagen-based plugs or fibrin glue used in selected cases; less effective in high-output fistulas.