Anal fistula

An anal fistula, also known as fistula-in-ano, is a chronic abnormal communication between the epithelialized surface of the anal canal and the perianal skin. This condition is usually the result of an infection in an anal gland that spreads to the skin. When the infection drains, it can create a passage or 'fistula'. It's a common condition in the field of colorectal surgery.

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Anal fistula diagram

Etiology and Pathogenesis

Anal fistulas are commonly associated with conditions that lead to inflammation and infection of the anal canal. These include Crohn's disease, a chronic inflammatory bowel disease, and previous anal abscesses. Other less common causes include tuberculosis, sexually transmitted infections, trauma, and malignancies. The formation of a fistula begins with infection of an anal gland, which subsequently forms an abscess. The abscess may then open to the surface and drain, creating a fistula tract.

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Clinical Presentation

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Patients with anal fistula often present with recurrent perianal abscesses, pain, and purulent discharge. Other symptoms may include irritation of the perianal skin, rectal bleeding, and, in some cases, fecal incontinence. The symptoms may be more pronounced during bowel movements.

Diagnosis

Diagnosis of an anal fistula is primarily clinical, based on patient history and physical examination. This may be complemented by imaging studies such as endoanal ultrasound, magnetic resonance imaging (MRI), or computed tomography (CT) scan to determine the exact course of the fistula tract, especially in complex or recurrent cases.

Treatment

The main goal of treatment for anal fistula is to ensure healing of the fistula tract while preserving the anal sphincter muscles to avoid incontinence. This can be achieved through several surgical options including fistulotomy, seton techniques, advancement flap procedures, fibrin glue, and the ligation of the intersphincteric fistula tract (LIFT) procedure. The choice of procedure depends on the location and complexity of the fistula, as well as the surgeon's expertise.

Prognosis

The prognosis after treatment of anal fistula is generally good, although recurrence is not uncommon, particularly with complex fistulas. Successful treatment significantly improves the quality of life by alleviating symptoms and preventing recurrent infections.

References

• [1] Vogel JD, Johnson EK, Morris AM, et al. (2020). Clinical Practice Guideline for the Management of Anorectal Abscess, Fistula-in-Ano, and Rectovaginal Fistula. Diseases of the Colon & Rectum, 63(12), 1622–1632.
• [2] Zanotti C, Martinez-Puente C, Pascual I, Pascual M, Herreros D, García-Olmo D. (2007). An assessment of the incidence of fistula-in-ano in four countries of the European Union. International Journal of Colorectal Disease, 22(12), 1459-1462.

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