Anal Fissure vs. Fistula: What Are the Differences?

Though they may have similar symptoms in some cases, anal fissures and fistulas are different conditions. An anal fissure is a crack or a tear in the tissue of the anus. A fistula is when a tunnel or connection forms between two organs or the organ and the skin.

Fissures and fistulas can both cause pain and bleeding. However, they are treated differently, so it’s important to tell them apart.

This article will explain the differences between an anal fissure and a fistula and how each condition is diagnosed and treated.

Symptoms

An anal fissure and a fistula can have similar symptoms. Rectal bleeding and pain during bowel movements are symptoms of both conditions. But other signs and symptoms of these conditions can help differentiate between them.

The symptoms of an anal fissure can include:

• Rectal bleeding
• Pain during a bowel movement (dyschezia)
• Pain that lasts a long time, even hours, after a bowel movement
• Tenderness or discomfort in the anal area
  

The symptoms of a perianal fistula can include:

• Discharge from the fistula (including blood, mucus, or other fluid)
• Fever
• Incontinence (leaking stool)
• Pain in the anal area (the bottom)
• Pain when going to the bathroom 
  

Causes

A fistula and a fissure form in different ways and may be associated with other conditions.

Anal Fissure

An anal fissure begins as a tear in the lining of the anus. It’s believed that many acute fissures (those that come on suddenly) may be due to tension in the muscles of the anus.

However, there are several other possible reasons for a fissure, especially for those that are long-lasting (chronic), including:

• Constipation: Hardened stool that is difficult to pass
• Diarrhea: Loose or watery stools that can occur several times a day
• Sexually transmitted infections (STIs): Infections that are transmitted from one person to another through intimate contact
• Inflammatory bowel disease (IBD): Chronic conditions that cause inflammation in the intestines and other parts of the body
• Human immunodeficiency virus (HIV): Weakens the immune system
• Childbirth: Can cause a tear or damage to the anus
• Other types of trauma to the anal area
• Tuberculosis: An infection with the bacterium Mycobacterium tuberculosis, which is an uncommon cause of a fissure
  

Fistula

A fistula is a connection between two internal organs or an organ and the skin that shouldn’t be there. The development of a fistula in the anal area commonly begins with an infection. It starts as an abscess, which is a pocket of pus. In some cases, this may create a lump or a bump under the skin in the anal area.

This abscess may eventually break open, creating a passage between two organs, a fistula. A fistula can form between:

• The anus and the skin
• The anus and the vagina (rectovaginal fistula)
• The skin and a part of the intestine
  

Some of the underlying causes of a fistula include:

• Cancer
• Crohn’s disease: A form of IBD that affects the entire digestive system
• Infection
• Radiation therapy: Might be used to treat some forms of cancer
• Surgery: Including intestinal resections (removal)

Diagnosis

There is some overlap in how an anal fissure and a fistula are diagnosed.

Anal Fissure

A fissure may be diagnosed by a healthcare provider after learning of your symptoms and after conducting a physical exam, such as a digital rectal exam. Let your provider know of any bleeding, itching, and burning you have had.

A history of changes in bowel movements is also important to bring up, including diarrhea and constipation. The duration of symptoms, such as how many times a day or week, is important. Keeping a diary of symptoms can be helpful when working with a healthcare provider.

In some cases, the fissure will be seen during a physical exam of the anal area. Other tests can include:

• Anoscopy: A tool is gently inserted into the anus to see the tissues there.
• Colonoscopy: A flexible tube with camera and a light on the end is inserted into the rectum and up into the colon.
• Flexible sigmoidoscopy: This is similar to a colonoscopy, except the tool is only used to see the first section of the large intestine, the sigmoid colon.
• Proctoscopy: This is similar to an anoscopy, but can see further up, beyond the anus, and into the rectum.

Fistula

Because a fistula begins as an abscess, a diagnosis of the abscess might be the first step. An abscess might be seen during an exam by a healthcare provider.

In some cases, a digital rectal exam is done. A gloved, lubricated finger is quickly inserted into the rectum to check for any lumps.

Tests that might be used to diagnose a fistula in complex situations include:

• Anoscopy
• Computerized tomography (CT) scan: Uses X-rays to create cross-sectional images of the organs and tissues in the abdomen
• Fistulography: An X-ray with contrast that's used to examine a fistula
• Magnetic resonance imaging (MRI): Uses strong magnetic fields and radio waves to take images of the abdomen and pelvis
• Proctoscopy
• Ultrasound: Uses sound waves

Treatment

Anal fissures and fistulas will be treated differently, so it’s important to get an accurate diagnosis.

Anal Fissure

An anal fissure may heal on its own with some at-home treatments, such as over-the-counter (OTC) medications and lifestyle changes. More complex or persistent fissures may need treatment with prescription medications or surgery. Treatments include:

• Diet: Some changes to diet may be recommended by a healthcare provider, such as eating more foods with fiber or taking a fiber supplement, and drinking more water.
• Lifestyle: A healthcare provider might recommend using a bidet instead of wiping after a bowel movement, using a sitz bath (soaking your bottom in a shallow pan of warm water), and avoiding sitting too long on the toilet to ease pain and discomfort.
• OTC: If constipation contributes to the problem, a stool softener might be recommended in addition to changes in diet and lifestyle.
• Prescription medications: Topical medications include nitroglycerin, calcium channel blockers, and creams that might relieve pain by applying them directly to the anus. Oral drugs might be recommended when topical ones aren’t providing relief and might include calcium channel blockers. Botox (botulinum toxin) injection is also an option.
• Surgery: In some cases, when a fissure isn’t healing with more conservative methods, surgery might be used to treat the fissure and prevent a recurrence. The most common surgery is a lateral internal sphincterotomy. Other types of fissure surgery are fissurectomy or anal advancement flap surgery.

Fistula

An abscess might be treated with antibiotics or drainage, and a fistula might be treated with a seton or medications.

Abscess treatment or drainage: If an abscess is found before it forms into a fistula, it may be treated with antibiotics, which might stop the advancement to a fistula. An abscess might also be treated by draining the pus that has formed from the infection. Drainage is usually done as an outpatient procedure.

Setons: A seton is a loop of material that’s threaded through the tract of the fistula. It’s made of flexible materials such as silicone, nylon, silk, or a surgical suture. A seton keeps the fistula tunnel open so that any pus or other fluid can drain and the fistula can heal.

Medications: Prescription medications might be used to help the abscess and/or the fistula heal. Antibiotics can help clear up an infection. If the fistula is associated with another condition, such as Crohn’s disease, treating the underlying illness with medications may be part of the healing process.

Surgery: Different types of surgery might be used to heal a fistula. This can include closing one side of the fistula tract or opening it completely and cleaning it out so that it may heal cleanly. 

Ostomy surgery may be needed in complex cases. In this procedure, part of the intestine is brought through the wall of the abdomen, creating a stoma. Stool leaves the body through the stoma and is caught in an appliance worn on the abdomen. The appliance is emptied into a toilet when needed. Sometimes the ostomy is removed when the fistula heals.

For situations in which a fistula keeps occurring, surgery may be done to remove the rectum and the anus. In this case, the ostomy will become permanent.

Prevention

It won’t always be possible to prevent a fissure or a fistula. However, there are a few things to keep in mind if you are at risk of developing one of these problems or have had them in the past.

Fissure

Fissures might occur with constipation or diarrhea, so it’s worth paying attention to bowel habits and ensuring that stool is soft and easy to pass. Exercise, dietary fiber, hydration, and avoiding straining on the toilet may help prevent an anal fissure.

Anal Fistula

A fistula may not be preventable in some cases. If you have Crohn’s disease, ensuring the condition is well-managed may help prevent complications such as a fistula. If you are receiving bowel cancer treatment, including radiation or surgery, ask a healthcare provider about fistula prevention.

General advice to maintain good bowel habits includes not sitting on the toilet too long or straining, drinking enough water, eating fiber, and getting regular exercise. See a healthcare provider regularly and especially when something seems different about bowel movements.

Summary

Anal fissures and fistulas both affect the area in and around the anus, but they are treated differently. For that reason, it’s important to see a healthcare provider about pain or bleeding from the rectum to get a diagnosis and treatment.

A Word From Verywell

Having symptoms with a bowel movement can be upsetting and frustrating. Many people are concerned that any bleeding or pain is cancer, but anal fissures are more common, and anal fistulas can be associated with certain other conditions, such as Crohn’s disease.

Caring for your digestive health includes everything from diet and hydration to exercise to seeing healthcare providers regularly. It can be embarrassing to talk about bowel movements, but it is nothing your providers haven’t heard before, and they are trained to help you with any issues.