Anal Fissure

An anal fissure is a small tear or split in the tissue lining the anus. It is common. Sharp pain arising particularly as the bowels are opened, and bright red bleeding, are the typical complaints.

An anal fissure can be confused with haemorrhoids, but the two are different conditions.

Why does an anal fissure happen?

The commonest cause is a hard, bulky stool damaging the tissue as it passes through the anus. Long-standing constipation and excessive straining are therefore important risk factors.

Frequent diarrhoea, childbirth and trauma to the anal region can also lead to a fissure.

Less often, fissures related to conditions such as Crohn’s disease and certain infections can be seen. Where a fissure is in an unusual position, where there is more than one, or where it does not respond to treatment, another underlying condition may be looked for.

What are the symptoms?

The most characteristic symptom is severe, sharp or tearing pain that begins as the bowels are opened. The pain can carry on for minutes, and sometimes hours, after the stool has been passed.

Other symptoms include:

• Bright red blood on the paper or on the surface of the stool
• Fear of opening the bowels
• Constipation that steadily worsens
• Burning or tenderness around the anus
• In a chronic fissure, a small skin tag beside the tear

Why is an anal fissure so painful?

Once the fissure has formed, the muscle inside the anus — the internal anal sphincter — can contract as a reflex.

That contraction reduces the blood flow to the area and makes the wound harder to heal. So:

Fissure → pain → sphincter spasm → reduced blood flow → delayed healing → the fissure persists

a cycle can develop.

This mechanism matters for understanding how an anal fissure is treated.

What are acute and chronic anal fissures?

A newly developed fissure is called an acute anal fissure, and a substantial proportion of these can heal with appropriate treatment.

In fissures that have gone on for a long time the wound can become deeper; the edges can thicken and a skin tag can develop on the outside. These are called chronic anal fissures, and they can be harder to treat.

Are an anal fissure and haemorrhoids the same thing?

No.

Haemorrhoids are related to enlargement and prolapse of the vascular cushions in the anal canal, whereas an anal fissure is a tear in the lining of the anus.

Because bright red bleeding can be seen in both, patients often confuse the two.

How is the diagnosis made?

In most patients a typical history and careful examination of the anal region are enough for the diagnosis.

But not every bleed from the back passage is a fissure or a haemorrhoid. Depending on the patient’s age, complaints, family history and accompanying findings, further investigations such as rectoscopy or colonoscopy may be needed.

How is an anal fissure treated?

The first aim of treatment is to keep the stool soft and to break the fissure–spasm cycle.

Softening the stool

Adequate fluid intake, an appropriate amount of fibre and a regular bowel habit matter. Where needed, stool-softening medicines can be used on a doctor’s advice.

A patient who puts off opening their bowels because of the pain makes the constipation worse and the fissure worse with it.

A warm sitz bath

Warm water can bring relief in some patients by reducing anal sphincter spasm and pain.

Local medical treatments

In chronic fissures, local treatments containing glyceryl trinitrate or a calcium channel blocker can be used to reduce the pressure in the anal sphincter and help healing.

Because these medicines can have side effects, it is appropriate to use them on a doctor’s advice.

Can Botox be used?

Yes. In some chronic anal fissures that do not respond adequately to medical treatment, botulinum toxin (Botox) can be injected into the internal anal sphincter.

The aim is to relax the muscle temporarily, reduce the spasm and give the fissure the chance to heal.

Is an operation needed?

Surgery can be considered in chronic anal fissures that resist treatment.

One of the most effective surgical methods is lateral internal sphincterotomy. In the procedure a small part of the internal anal sphincter is divided, reducing the pressure in the muscle.

The success rate is high, but because there is a risk of impaired control of wind or stool the decision to operate should be made for the individual patient.

Can an anal fissure turn into cancer?

No. An anal fissure is not a precancerous lesion and does not turn into cancer.

But where there is bleeding, pain or a non-healing wound in the anal region, it should not automatically be assumed to be a fissure. Lesions that do not heal despite treatment, or that look unusual, need to be assessed.

When should a doctor be seen?

An assessment should be made where there is repeated bleeding from the back passage, severe pain, long-standing constipation, a fissure that does not heal despite treatment, weight loss, or an unexplained change in bowel habit.

In brief

An anal fissure = a small tear in the lining of the anus.

Its most typical presentation is:

Passing a stool → sharp pain → bright red bleeding

Treatment rests on softening the stool and reducing anal sphincter spasm. Appropriate treatment early on can prevent it from becoming chronic.

Note: This information is provided for general patient education. Because bleeding from the back passage can have different causes, bleeding that is new or that recurs should not be attributed to haemorrhoids or an anal fissure alone.