Anal Fissure

An anal fissure is a tear in the anoderm, the sensitive lining of the anal canal. Most occur in the midline at the back of the anal canal, and most begin after a hard or difficult bowel motion.

The pain is caused by more than the tear itself. The internal anal sphincter goes into spasm, which worsens the pain and reduces blood flow to an area that already has a relatively poor blood supply. The fissure then struggles to heal, and a cycle of pain, spasm and further tearing becomes established. Most treatment is aimed at breaking that cycle rather than at the tear directly.

An acute fissure is a recent, superficial tear that usually heals within a few weeks. A chronic fissure has been present for longer, typically more than six weeks, and often develops additional features such as a small skin tag at the outer edge or a thickened area of tissue inside the anal canal.

The pattern of symptoms is usually characteristic, and the diagnosis can often be suspected from the history alone.

Bleeding that is heavy, dark, or mixed through the stool is not typical of a fissure and should be assessed rather than assumed to be related.

• Sharp, tearing or burning pain during a bowel motion, often described as passing broken glass.
• Pain that continues after the motion, sometimes for minutes to hours, as the sphincter goes into spasm.
• Small amounts of bright red blood, usually on the toilet paper or on the surface of the stool rather than mixed through it.
• Anxiety about opening the bowels, which often leads to putting it off and to constipation, worsening the problem.
• Itching, irritation or a small lump at the anal opening, more common with longstanding fissures.

Assessment begins with a careful history. The character and timing of the pain, its relationship to bowel motions, the pattern of bleeding and the history of bowel habit together usually make the diagnosis clear before examination.

Examination is gentle and adapted to the level of discomfort. A fissure can often be seen by careful inspection alone, and internal examination is frequently deferred at the first consultation because it is too painful to perform reliably. Treatment can usually begin on the basis of the history, with review once the pain has settled.

Part of assessment is confirming that the problem is a simple fissure and not something that resembles one. A fissure that is not in the usual midline position, multiple fissures, an unusually large or irregular tear, associated swelling or discharge, or failure to respond to treatment will prompt further assessment. Conditions that can present similarly include Crohn’s disease and other inflammatory bowel disease, perianal abscess and fistula, certain infections, skin conditions affecting the perianal area and, rarely, anal cancer.

A change in bowel habit, weight loss, anaemia, a strong family history of bowel cancer, or bleeding that does not fit the fissure pattern will prompt consideration of colonoscopy. A fissure and a second, unrelated problem can coexist.

Correcting difficulty passing stool is the foundation of treatment and is as important as any medication. Fissures that heal on medical treatment alone commonly recur if bowel habit is not addressed. The aim is a soft, formed stool that passes without straining.

• Increase dietary fibre steadily, allowing time to adjust rather than making an abrupt change.
• Maintain a good fluid intake through the day.
• Use a stool softener or fibre supplement where diet alone is not enough, as advised.
• Avoid straining and avoid prolonged sitting on the toilet.
• Warm baths can ease sphincter spasm and provide symptomatic relief.

Topical diltiazem and glyceryl trinitrate (GTN) are both used as first-line medical treatment, and either may be prescribed. Both work by relaxing the internal anal sphincter, which relieves the spasm and improves blood flow to the fissure so that healing can occur. The choice, strength and instructions for use will be provided specifically for you.

Treatment is normally continued for six to eight weeks. Improvement in pain is often noticed within the first week or two, but the full course matters, and stopping early once the pain settles is a common reason for the fissure to recur. Headache is the most common side effect and is more frequent with GTN than with diltiazem. Local irritation can also occur. If one preparation is not tolerated, the other can often be substituted.

Used together with the bowel measures above, medical treatment resolves the majority of fissures without any need for surgery.

Where a fissure has not healed despite a proper course of medical treatment and good bowel management, surgical options are considered. The priority is to achieve healing while protecting continence.

Botulinum toxin injection relaxes the internal anal sphincter more reliably than topical treatment and without depending on regular application. The effect lasts around three months, generally long enough for the fissure to heal. Some patients notice temporary reduced control of wind, which settles as the effect wears off.

Fissurectomy involves removing the fibrotic edges and base of a chronic fissure, converting a longstanding non-healing wound into a fresh one that can heal. It is often performed together with botulinum toxin injection. Both are day procedures, and bowel measures are continued throughout recovery. The reasoning behind the recommended approach, the alternatives and the expected benefits and risks are discussed in full before any decision is made.