An anal fissure is a small tear in the thin, moist tissue (mucosa) that lines the anus. It causes sharp, often severe pain during and after opening the bowels, along with bright red rectal bleeding. Despite being a very common condition, many people mistake it for haemorrhoids and delay seeking appropriate treatment — which is a shame, because with the right management, the vast majority of anal fissures can be healed without surgery.
What Causes an Anal Fissure?
Anal fissures most commonly develop as a result of passing a large or hard stool that stretches and tears the anal lining. Once a tear has formed, the internal anal sphincter — the ring of muscle controlling the anus — goes into spasm, reducing blood flow to the area and preventing healing. This creates a cycle of pain, spasm and poor healing that keeps the fissure open.
Common contributing factors include constipation and straining, diarrhoea, childbirth, and low dietary fibre intake. In most cases no specific underlying cause is found — but occasionally a fissure may be associated with Crohn's disease, sexually transmitted infections or other conditions.
Symptoms
The characteristic presentation of an anal fissure includes:
- Sharp, intense pain during and after opening the bowels — often described as passing broken glass
- Pain that may last for minutes to hours after defaecation
- Bright red blood on the toilet paper or on the surface of the stool
- Visible tear or crack in the skin around the anus
- A small skin tag (sentinel pile) at the outer edge of a chronic fissure
Acute versus Chronic Fissures
An acute fissure is a fresh tear, typically with bright red edges. Most acute fissures heal within six weeks with conservative treatment. A chronic fissure has been present for longer than six weeks and shows signs of established damage — thickened edges, a visible internal sphincter fibre at the base, and often a sentinel pile. Chronic fissures are less likely to heal without specific treatment.
Treatment Options
Conservative Measures
Increasing dietary fibre and fluid intake to soften the stool is the cornerstone of treatment. Warm baths after opening the bowels help relax the sphincter and relieve pain. Topical anaesthetic creams provide short-term symptomatic relief.
Topical Treatments
Topical glyceryl trinitrate (GTN) cream relaxes the internal anal sphincter, improving blood flow to the fissure and promoting healing. It heals around 60 to 70 percent of chronic fissures but can cause headaches as a side effect. Diltiazem cream is an alternative with a better side effect profile and similar efficacy.
Botulinum Toxin Injection
Injection of botulinum toxin into the internal sphincter temporarily relaxes the muscle, allowing healing to occur. It is performed under local or general anaesthetic as a day case procedure and has a healing rate of around 70 to 80 percent for fissures that have not responded to topical treatment.
Lateral Internal Sphincterotomy
The most effective surgical treatment, with a healing rate over 90 percent. A small cut is made in the internal sphincter to reduce its tone and relieve spasm. Performed under general anaesthetic as a day case. The small risk of altered continence is carefully discussed at consultation.
When Should You See a Specialist?
If your symptoms have not improved after four to six weeks of conservative management, or if you are experiencing significant pain that is affecting your quality of life, specialist assessment is appropriate. Most patients are pleasantly surprised to find that effective treatments are available and that surgery is by no means inevitable.