Perianal Crohn’s 101: Abscess vs Fistula vs Fissure (What’s What)
Last Updated Jan 15, 2026
Perianal Crohn’s refers to Crohn’s disease symptoms and complications that happen in the area around the anus (the opening where stool leaves the body). These issues can feel personal and stressful, but they are also common, treatable, and worth bringing up early. The tricky part is that several different problems can cause similar discomfort, and the words can sound alike, abscess, fistula, and fissure, even though they are not the same thing.
What “perianal Crohn’s” means (and why it can be confusing)
Crohn’s disease can cause ongoing inflammation anywhere in the digestive tract, including the rectum and the skin and glands around the anus. When inflammation affects this area, symptoms may include perianal pain, a tender lump, drainage that stains underwear, itching or burning, and bleeding. Some people notice symptoms mainly with sitting or bowel movements, while others notice discomfort that lasts all day.
Perianal symptoms can also overlap with non-Crohn’s problems (like hemorrhoids), and more than one issue can happen at the same time. For example, a small tear in the anal lining can sting and bleed, but it can also make the area feel tight and sore. An infection can cause swelling and throbbing pain, and later lead to ongoing drainage. Because of that overlap, self-labeling a symptom as “just irritation” can sometimes delay care.
Many care teams treat perianal Crohn’s with a step-by-step plan that aims to (1) check for infection, (2) map what is happening under the skin, and (3) calm inflammation over time. Clear names for each problem help patients and clinicians communicate and choose next steps.
Abscess vs fistula vs fissure (what each one is, and what it may feel like)
Abscess: An abscess is a pocket of pus caused by infection. In Crohn’s disease, abscesses can develop around the anal area and may cause a swollen, red, tender lump, fever, painful bowel movements, or pus draining from the anus. Abscess symptoms can escalate quickly, especially when infection is involved. [1]
Fistula: A fistula is an abnormal tunnel, often from the anal canal or rectum to the skin near the anus. In Crohn’s, perianal fistulas may cause a tender area around the anus, pain or irritation (often worse with sitting or bowel movements), and drainage that can be pus, blood, or even stool. A fistula can form after an abscess, especially when infection tracks its way to the skin surface. [2]
Fissure: An anal fissure is a small tear in the thin lining of the anus. Fissures often cause sharp pain during bowel movements, pain that can linger for hours afterward, and bright red blood on stool or toilet paper. Some people also notice a visible crack or a small skin tag near the tear. [3]
How clinicians tell them apart (and which symptoms are urgent)
Diagnosis usually starts with a careful history and an exam, but perianal Crohn’s often needs more than a quick look. Expert guidance commonly recommends combining imaging (often a pelvic magnetic resonance imaging, MRI, fistula protocol) with an exam under anesthesia by a colorectal surgeon to fully understand fistulas and abscesses below the surface. About 26% of people with Crohn’s may develop a perianal fistula, so clinicians take these symptoms seriously even when the outside skin looks “mostly normal.” [4]
Some symptoms are often treated as urgent because they can signal infection or a complication that should not wait. Examples include fever or chills, rapidly worsening perianal pain, spreading redness or swelling, and new or increasing pus-like drainage. Johns Hopkins notes that anorectal abscess needs immediate medical attention, and colorectal surgery guidance also highlights that abscesses can come back or later appear as a fistula, and that Crohn’s-related perianal fistula care is often primarily medical, with procedures used to control infection and support healing. [5]
Even when symptoms seem “manageable,” persistent drainage and irritation often do not resolve on their own when a fistula is present, and many cases require clinician-guided treatment planning. [6]