Why is perianal abscess prone to develop into anal fistula?

Nov 14, 2025 Source: Cainiu Health

Dr. Li Jingxiang

Introduction

Perianal abscesses tend to develop into anal fistulas, primarily due to factors such as unremoved infection foci, spontaneous rupture of the abscess, incomplete treatment, unique anatomical structures, and repeated infection or irritation. Essentially, the two conditions represent different stages of the same disease. If symptoms such as redness, swelling, pain, or pus discharge around the anus occur, prompt medical attention is recommended. Perianal abscesses are mostly caused by infection of the anal glands.

Perianal abscesses are prone to develop into anal fistulas, primarily due to unremoved infection foci, spontaneous rupture of the abscess, incomplete treatment, unique anatomical structure, and repeated infection or irritation. Essentially, the two conditions represent different stages of the same disease. If symptoms such as redness, swelling, pain, or pus discharge around the anus occur, prompt medical attention is recommended.

1. Unremoved infection focus: Perianal abscesses are mostly caused by infection of anal glands. The infection site lies deep within perianal tissues. If only superficial anti-inflammatory treatment is applied without completely eliminating the source, residual bacteria continue to multiply and gradually erode surrounding tissues, leading to the formation of a fistula tract.

2. Spontaneous rupture of abscess: As an abscess matures, it may spontaneously rupture. After the external opening heals, a false healing occurs, trapping pus inside. Persistent bacterial growth and repeated inflammation in the area eventually result in chronic anal fistula formation.

3. Incomplete treatment: If the internal opening is not identified during incision and drainage of the abscess, or if drainage is inadequate, residual pus in tissue spaces can gradually form an abnormal channel connecting the perianal skin to the anal canal, progressing into an anal fistula.

4. Unique anatomical structure: The perianal region has rich vascularity and loose connective tissue, making infections easy to spread and difficult to localize. Once an abscess forms, it tends to extend toward the anal canal, penetrate the anal mucosa to create an internal opening, and ultimately develop into a complete anal fistula.

5. Repeated infection and irritation: After recovery from a perianal abscess, poor perianal hygiene or unresolved triggers such as constipation or diarrhea may lead to reinfection of the anal glands. Recurrent inflammation causes fibrosis and permanent fistula tract formation, resulting in anal fistula.

To maintain perianal health, it is important to keep the area clean and dry, avoid prolonged sitting or standing, follow a light diet avoiding spicy and irritating foods, and maintain regular bowel movements. These measures help reduce irritation to perianal tissues and lower the risk of recurrent infection.

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Can anal fistula not be cured?

If the anal fistula is simple, with only one fistula tract, a clearly defined internal opening, and no branches or multiple external openings, timely undergoing standardized surgical treatment such as fistulotomy or seton placement at a正规 hospital can completely remove the fistula tract and internal opening. With proper postoperative wound care according to medical advice and prevention of infection, most cases of such anal fistulas can be cured彻底, and the recurrence rate is low.

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How is anal fistula treated?

Treatment options for anal fistula include fistulotomy, seton placement, fistulectomy, minimally invasive procedures, and adjunctive medical therapy. Surgery remains the primary method for definitive treatment, and the choice of procedure should be based on the type of fistula and individual patient condition. If symptoms such as recurrent pus discharge, worsening pain, or fever occur, prompt medical attention is recommended. Complete incision of the fistula tract allows open drainage of the wound.

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What are the differential diagnoses for perianal abscess?

Differential diagnoses of perianal abscess include anal fistula, perianal folliculitis, infected sebaceous cysts, pilonidal sinus, and anorectal tumors. These conditions must be distinguished through symptoms, physical signs, and diagnostic tests to avoid misdiagnosis and delayed treatment. If symptoms such as redness, swelling, heat, pain around the anus, or fever occur, prompt medical evaluation is recommended for accurate diagnosis. Anal fistulas often have a history of perianal abscess and typically present with recurrent external openings discharging pus.

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How long after anal fistula surgery should there be no bleeding?

There is no fixed standard for the time of cessation of bleeding after anal fistula surgery. Generally, bleeding significantly decreases and gradually stops within 3 to 7 days postoperatively. The exact duration depends directly on the size of the surgical wound, individual coagulation function, and postoperative care. Patients with smaller wounds and proper care tend to recover faster, while those with larger wounds or inadequate care may experience prolonged bleeding. In terms of diet, it is recommended to consume more liquid foods such as porridge and well-cooked noodles.