What are the symptoms of anal fistula?

Written by Chen Tian Jing

Colorectal Surgery

Updated on April 11, 2025

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The clinical symptoms of anal fistula are mainly manifested as intermittent discharge of secretion from the local external opening near the anus, accompanied by varying degrees of pain in the anal area, and occasionally, pus is expelled with the stool. The main reason for its formation is that the anal fistula not only has an external opening, but also an internal opening near the dentate line of the anal canal. The internal opening discharges pus intermittently due to the stimulation of local inflammation. The composition of an anal fistula includes the internal and external openings, as well as the fistula tract that connects them; therefore, simply using medication cannot completely eliminate this lesion. The treatment of anal fistula is mainly surgical, aimed at removing the local lesion, with the principle of preserving the anal sphincter to avoid damage to it, which could affect the patient's future life.

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Written by Chen Tian Jing

Colorectal Surgery

1min 1sec

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Anal fistulas secondary to which disease?

An anal fistula generally originates from a perianal abscess, which is an infection focus formed near the anal sinuses in the local area of the anus. During its onset, there is obvious local redness, swelling, heat, and pain accompanied by the formation of a pus cavity containing pus. As the condition of the perianal abscess worsens, the local pus cavity will rupture and discharge pus, thus forming an anal fistula. After the rupture of a perianal abscess, its external opening cannot heal by itself, and there will be intermittent recurring discharge of pus. Therefore, it is necessary to carry out surgical treatment as soon as possible after the formation of an anal fistula, to prevent the enlargement of the local pus cavity or thickening of the fistula wall, which complicates later surgery and treatment and significantly impacts the patient's normal life.

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Written by Deng Heng

Colorectal Surgery

54sec

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What are the symptoms of anal fistula?

An anal fistula generally refers to a tract left behind after an anal abscess bursts on its own or is surgically opened. It usually consists of a primary internal opening and a secondary external opening. The main clinical manifestations, or primary symptoms, are: The first is discharge of pus, which occurs due to recurrent infections in the anal fistula; The second is pain. When the external opening is closed, the pus inside cannot drain properly, or when drainage is poor, this leads to accumulation of pus in the fistula tract, causing localized pain; The third is itching. Continuous irritation of the skin around the external opening by pus draining from the fistula tract can cause itching around the anus and may lead to symptoms like anal eczema.

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Written by Chen Tian Jing

Colorectal Surgery

1min 13sec

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How to deal with the internal opening of an anal fistula?

The internal opening of an anal fistula is generally located at the site of inflammation in the anal crypt. The primary reason for the formation of an anal fistula is the repeated outbreaks at the anal crypt, which lead to further infection and the formation of a perianal abscess. When the abscess cavity ruptures, it forms an external opening and the anal fistula. Surgical treatment is required for the internal opening of an anal fistula, generally involving a seton procedure that threads a line through the internal opening and part of the sphincter muscle, gradually cutting and draining the area slowly. If the inflammation at the internal opening is significant, it may also be necessary to excise part of the infected site in the anal crypt. Post-surgery care of the internal opening of an anal fistula primarily involves dressing changes, requiring daily thorough disinfection of the local area, ensuring clear drainage, to allow the granulation tissue at the internal opening to grow freshly, and to slowly heal the wound without infection. (Medication should be taken under the guidance of a doctor.)

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Written by Deng Heng

Colorectal Surgery

41sec

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How long does it take for an anal fistula to form?

An anal fistula is a tract left after an anal abscess bursts spontaneously or is surgically drained, generally consisting of a primary internal opening, a fistula tract, and a secondary external opening. Thus, an anal fistula and an anal abscess represent two stages of the same disease: initially, there is an anal abscess, and then, after the pus from the abscess is drained, an anal fistula forms. Typically, the transformation from an anal abscess to an anal fistula takes about two to three months, meaning that an anal fistula can form about three months after the abscess bursts.

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Written by Yang Dong

Colorectal Surgery Department

28sec

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What are the symptoms of an anal fistula?

Anal fistula is one of the common diseases in proctology. The most typical symptom of anal fistula is recurrent anal induration, accompanied by swelling, pain, and pus discharge, often with a ruptured external opening. During the quiescent phase, a hard cord can be felt leading from the ruptured external opening to the inside of the anus; during the acute inflammatory phase or abscess phase, pressing may cause pus to ooze from the ruptured opening.