What are the consequences of not treating an anal fistula?

Written by Chen Tian Jing
Colorectal Surgery
Updated on March 22, 2025
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If an anal fistula is not promptly treated with surgery, it may lead to an increase in the number of local branches or a thickening of the fistula wall. If the branches of the anal fistula extend to the ischiorectal fossa, it may also lead to pelvic infections. Moreover, if the anal fistula persists for a long time or if there is significant local inflammatory stimulation, it may even lead to cancerous changes in the fistula. Therefore, once an anal fistula is discovered and diagnosed, it is recommended to promptly undergo surgical treatment with fistulotomy and seton placement. Post-surgery, it is crucial to ensure thorough disinfection of the local wound, debridement, and dressing changes, which are very important for the recovery of the wound. This helps prevent pseudohealing, ensuring that the anal fistula heals completely and preventing recurrent episodes.

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Written by Chen Tian Jing
Colorectal Surgery
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Symptoms of cancerous transformation in anal fistula

The vast majority of anal fistulas do not undergo malignant transformation. However, there is a possibility of cancerous changes if an anal fistula that has repeatedly recurred over a long period is not treated aggressively, or if the inflammation of the fistula tract is severe. When an anal fistula undergoes malignant transformation, the secretion from the local fistula tract increases and is accompanied by a foul smell, and there may even be ulceration of the local fistula tract mucosa. Further surgical procedures, such as fistulotomy with seton placement, are required, and the excised fistula tract suspected of high-grade malignant transformation should be sent for pathological examination. If malignant transformation is confirmed, further pelvic MRI examinations are necessary to determine whether there is local and surrounding lymph node metastasis.

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Written by Yang Dong
Colorectal Surgery Department
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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.

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Written by Chen Tian Jing
Colorectal Surgery
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The difference between perianal abscess and anal fistula

Perianal abscesses and anal fistulas both belong to local infectious diseases of the anus. A perianal abscess represents the acute phase of infection, characterized by significant localized subcutaneous swelling, heat, pain, and the formation of pus and abscesses. Once the pus breaks through the skin and discharges, it naturally forms an anal fistula. Anal fistulas represent the later stages or dormant phases of local infections. Both perianal abscesses and anal fistulas require surgical treatment. The surgical method for perianal abscesses mainly involves a one-time radical surgery for the abscess, while the surgical approach for anal fistulas primarily involves fistulotomy with seton placement, followed by regular wound cleaning and dressing changes post-surgery.

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Written by Chen Tian Jing
Colorectal Surgery
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Do anal fistulas need surgery even if there are no symptoms?

After the formation of an anal fistula, it does not always lead to acute episodes over a long period. Acute episodes of an anal fistula, causing infectious symptoms, occur only when there is a severe localized damp-heat condition. Therefore, the symptoms of an anal fistula are intermittent. The absence of symptoms does not mean that the anal fistula is completely cured or will not recur. Therefore, if an anal fistula is diagnosed, it is necessary to undergo surgical treatment as soon as possible to avoid repeated episodes due to lack of active treatment. Long-term repeated episodes of an anal fistula can lead to thickening of the fistula wall and an increase in branching. Even if an anal fistula is not actively treated over many years, it may even induce carcinogenesis in the local fistula wall.

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Written by Chen Tian Jing
Colorectal Surgery
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Symptoms of hemorrhoids and anal fistula

If there are concurrent hemorrhoids and anal fistulas, then the clinical manifestations primarily involve the combined symptoms of both conditions. The clinical manifestations of hemorrhoids mainly include recurrent prolapse of local swellings at the anus along with defecation bleeding or pain. As for anal fistulas, they primarily present with local infectious symptoms at the anus because anal fistulas have distinct external and internal openings. During acute episodes, there typically is intermittent discharge of pus from the external opening along with accompanying stabbing pain. If the patient also has hemorrhoids or an exposed anal fissure, it is recommended to proceed with surgical treatment as soon as possible. The only treatment method for anal fistulas is surgery. During the surgery, while excising the wall of the anal fistula tract, mixed hemorrhoids can also be removed simultaneously, achieving the purpose of complete cure.