Anal Fistula: Causes, Symptoms and Treatment
An anal fistula is a small tunnel that forms between the inside of the anal canal and the skin around the anus. It usually develops after an abscess and causes pain, swelling, and discharge.
Things worth knowing about "Anal Fistula"
An anal fistula is a small tunnel that forms between the inside of the anal canal and the skin around the anus. It usually develops after an abscess and causes pain, swelling, and discharge.
What Is an Anal Fistula?
An anal fistula is an abnormal, tunnel-like channel that connects the inner lining of the anal canal or rectum to the skin surrounding the anus. It most commonly develops as a result of a previously infected anal abscess that has either burst or been surgically drained, leaving behind a persistent passage. Anal fistulas are a common proctological condition and tend to affect men slightly more often than women.
Causes
The most frequent cause of an anal fistula is a preceding anal abscess -- a collection of pus near the anus. When such an abscess drains, it can leave a tract that does not heal properly. Other possible causes include:
- Crohn disease: A chronic inflammatory bowel disease strongly associated with perianal fistulas
- Tuberculosis or other specific intestinal infections
- Diverticulitis: Inflammation of pouches in the bowel wall
- Malignant tumors in the anal or rectal area
- Previous surgery or radiation therapy in the pelvic region
- Obstetric injuries following childbirth
Symptoms
Symptoms of an anal fistula can vary depending on severity. Common complaints include:
- Pain and pressure around the anus, especially when sitting or during bowel movements
- Purulent or bloody discharge from a small opening beside the anus
- Redness, swelling, and warmth of the perianal skin
- Itching or irritation of the skin around the anus
- Recurrent abscesses in the anal region
- Occasional fever when an active infection is present
Diagnosis
Diagnosis is typically established through a clinical examination by a proctologist or colorectal surgeon. The following diagnostic methods are commonly used:
- Inspection and palpation: Visual examination and gentle probing of the anal region to identify the external fistula opening
- Proctoscopy / rectoscopy: Endoscopic examination of the anal canal and lower rectum to locate the internal opening
- Pelvic MRI (Magnetic Resonance Imaging): The gold standard for precisely mapping the fistula tract and its relationship to the sphincter muscles
- Endoanal ultrasound: Ultrasound performed from within the rectum to assess the fistula course
- Fistulography: X-ray imaging after contrast injection into the fistula tract (less commonly used today)
Treatment
An anal fistula rarely heals on its own and almost always requires surgical treatment. The primary goal is complete elimination of the fistula tract while preserving the sphincter muscles to prevent fecal incontinence.
Surgical Procedures
- Fistulotomy: The fistula tract is laid open and left to heal from the inside out. Suitable for simple, superficial fistulas.
- Seton placement: A surgical thread (seton) is passed through the fistula to slowly cut through the sphincter or to keep the tract open for drainage and infection control.
- Advancement flap repair: The internal fistula opening is covered with a flap of rectal mucosa, sparing the sphincter muscle.
- LIFT procedure (Ligation of Intersphincteric Fistula Tract): The fistula tract is tied off and divided between the sphincter muscles.
- Fibrin glue or fistula plug: Biological materials are injected or inserted to seal the fistula channel. Less invasive but with lower success rates.
- Laser fistula therapy (FiLaC): Laser energy is used to obliterate the fistula tract from within.
Treatment in Crohn Disease
Fistulas associated with Crohn disease require a combined approach of medical therapy -- such as biologics like infliximab or adalimumab -- and surgical intervention. Close collaboration between gastroenterologists and surgeons is essential for optimal outcomes.
Prognosis and Complications
The likelihood of successful treatment depends on the type of fistula, its relationship to the sphincter, and any underlying conditions. Simple fistulas often respond well to surgery, while complex or Crohn-related fistulas carry a significantly less favorable prognosis and a higher risk of recurrence. Potential complications include:
- Recurrence of the fistula (relapse)
- Fecal incontinence if the sphincter is damaged
- Chronic wound infections
References
- Ommer A. et al. - S3 Guideline: Cryptoglandular Anal Fistulas. German Society of Coloproctology (DGK), 2016.
- Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. British Journal of Surgery, 1976; 63(1):1-12.
- World Gastroenterology Organisation (WGO) - Practice Guidelines: Inflammatory Bowel Disease. WGO, 2015.
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