Crohn’s Fistulas: Symptoms, Imaging Tests, and Treatment Options
Last Updated Jan 15, 2026
Perianal fistulas are a common and stressful complication of Crohn’s disease. A fistula is an abnormal tunnel that forms when inflammation reaches deeper layers of the bowel wall and connects to another area, often the skin near the anus. Because fistulas can branch, hide abscesses (pockets of infection), and affect continence muscles, care often involves both gastroenterology and colorectal surgery, with testing to map the tunnel before choosing a plan.
Fistula symptoms and how imaging tests help
Perianal fistula symptoms can vary from mild irritation to severe pain. Common signs include a tender swelling or lump near the anus, pain or burning with sitting or bowel movements, and ongoing drainage that can be pus, stool, or blood (sometimes noticed on underwear). Skin around the opening can become sore or itchy. Some fistulas are “quiet” on the surface but still connect to a deeper tract, which is one reason imaging can matter. The Crohn’s and Colitis Foundation notes that additional testing may include pelvic magnetic resonance imaging (MRI), endoscopic ultrasound (a specialized ultrasound done through the rectum), or an examination under anesthesia to understand how far the fistula extends and whether there are branches or infection. [1]
Imaging is mainly used to find the fistula’s route and check for abscesses that may need drainage. The American College of Radiology (ACR) rates MRI of the pelvis with and without contrast as “usually appropriate” as initial imaging when perianal disease such as an abscess or fistula is suspected, with endoanal ultrasound listed as an option that “may be appropriate” in some cases. [2]
Because abscess symptoms can overlap with fistula symptoms, it helps to recognize infection warning signs. The Crohn’s and Colitis Foundation lists possible abscess symptoms such as painful bowel movements, pus discharge, a swollen red tender lump near the anus, and fever, and notes that abscesses often need antibiotics and may also need surgical drainage. [3]
Crohn’s fistula treatment options (medical + surgical)
Crohn’s fistula treatment often follows a stepwise approach: control infection, keep any trapped fluid draining, and treat the underlying inflammation so the tract has a better chance to close. Plans differ based on whether the fistula is “simple” or “complex,” whether there is rectal inflammation, and whether an abscess is present.
Medication options commonly discussed include:
- Antibiotics for short-term symptom relief or infection control in some situations.
- Biologic medicines that target inflammation. The 2025 American College of Gastroenterology (ACG) guideline recommends infliximab for induction of remission in perianal fistulizing Crohn’s disease, suggests adalimumab, and suggests other advanced therapies such as vedolizumab, ustekinumab, and upadacitinib (strength of evidence varies). The guideline also suggests that adding antibiotics to infliximab or adalimumab may improve response for some people. [4]
Procedures are often part of treatment, especially for complex fistulas or when an abscess is present. The ACG guideline highlights the role of surgical evaluation (often including an exam under anesthesia) to identify abscesses and tracts, and describes setons (thin loops placed through the tract) as a common way to allow ongoing drainage, often done before starting immunosuppression. Other surgical techniques may be considered in selected situations after infection and inflammation are controlled.
For decision-making, helpful questions for a clinic visit often include: whether an abscess is suspected, what imaging showed about branching tracts, what the short-term plan is for drainage and symptom control, and how success will be tracked over time (symptoms plus follow-up assessment).