Anal fissure

An anal fissure is a tear in the mucosa of the anal canal, just inside the anal margin. It is a common condition causing pain on defecation in adults and children. Most anal fissures respond well to conservative or topical management. In refractory cases surgery may be required.

Are anal fissures common? (Epidemiology)^{1 2}

• Anal fissure is known to be a common condition. There are no recent prevalence figures but it is believed to have a lifetime incidence of around 11%.

• It can occur at any age, including children. However, it is most common between the second and fourth decades. Primary anal fissures are less common in the elderly.

• Prevalence is equal between men and women.

• Acute fissures are more common than chronic fissures.

Anal fissure causes (aetiology)¹

Anal fissures may be classed as:

• Acute: present for less than six weeks.

• Chronic: present for six weeks or more.

They may also be classed as:

• Primary: no apparent cause.

• Secondary: due to an underlying condition. For example:

  • Constipation - a hard stool tears the anal mucosa as it is passed.

  • Inflammatory bowel disease - ulceration as part of the inflammatory process.

  • Sexually transmitted infection.

  • Rectal malignancy.

The aetiology of primary anal fissures is not entirely clear. It is known they are associated with increased anal tone (tight anal sphincter muscles), although the cause of this is unknown. The subsequent relative ischaemia hinders the healing process. In children particularly, withholding of stool to avoid pain may worsen constipation and exacerbate the problem. Management options target reducing anal tone.

Primary fissures are usually benign and located in the posterior or anterior position. Secondary fissures are lateral or multiple.

Anal fissure symptoms and presentation³

The diagnosis is usually made on history and physical examination; however, further investigations are sometimes necessary.

Anal pain is experienced on defecation, traditionally described as feeling like passing shards of glass. Pain may persist for several hours after passing stool.

There may be bleeding on passing stools. If present, it is seen as bright red blood on the stool or toilet paper.

A thorough history should be taken to include:

• Bowel habit - constipation, diarrhoea, recent change.

• Associated symptoms - abdominal pain, weight loss, rectal discharge.

• Family history relating to inflammatory bowel disease and colorectal disease.

Bear in mind the possibility of sexual abuse in children, especially if there is no history of passing hard stools and other causes are not present.

Examination

Examine the abdomen, palpating for masses, organomegaly and faecal loading.

The fissure can be seen on external examination of the anus. Usually it is in the form of a linear split of the mucosa. Part the buttocks gently; if anal spasm prevents a view of the fissure, slight pressure on the margin of the anus may help. The majority of fissures are posterior and in the midline. Do not attempt a digital rectal examination (DRE) at the time of presentation, as this is very painful in the presence of an acute anal fissure. If features of the history suggest the need for DRE, this can be done at a later date following treatment or with analgesia/anaesthesia if need be.

Acute fissures have clear edges and are linear. Chronic fissures tend to be deeper and often associated with an external skin tag at the distal end. There may be fibres of the internal sphincter muscle visible in the base of the fissure. Secondary fissures are more likely to be multiple, lateral, or have irregular demarcation.

Diagnosis is clinical and further investigation is only required if there are features of underlying pathology.

Differential diagnosis¹

Appearance is diagnostic but other causes of anorectal pain include:

• Haemorrhoids - particularly if thrombosed.

• Abscess.

• Proctitis.

• Perianal sepsis.

• Proctalgia fugax.

Anal fissure treatment and management⁴

The management of primary anal fissures is generally non-operative and includes increased dietary fibre, warm baths, topical ointments and botulinum toxin injections. If these treatments are ineffective then surgical intervention may be considered. Secondary anal fissures require further investigation.

General

• Advise adults and children with anal fissure to take measures to keep stools regular and soft:

  • Adequate fluid intake.

  • Increase fibre content in the diet (whole grains, vegetables and fruit). Adults should aim for 18-30 g fibre per day.

  • Consider use of a laxative. Use bulk-forming laxatives (eg, ispaghula husk) for adults and osmotic laxatives (eg, lactulose) for children.

• Advise about pain relief (see below).

• Treat (or refer for) underlying conditions.

Pain relief

Options in primary care include:

• Simple oral analgesia. Paracetamol or ibuprofen as required.

• Warm baths.

• Consider prescribing glyceryl trinitrate (GTN) ointment:³

  • For adults who have had a fissure for over a week without improvement. (Use for children advised in secondary care only.)

  • Apply twice a day for up to eight weeks.

  • GTN relaxes smooth muscle, thus reducing anal tone.

  • Cochrane reviews suggest a cure rate marginally more effective than placebo in either acute or chronic fissures.

  • 30% have headache as a side-effect.

  • In the UK, 0.4% GTN ointment (Rectogesic®) is the only licensed topical GTN for anal fissure. 0.2% may be as effective and with fewer side-effects but it is currently 'unlicensed use' and has to be made up by the pharmacist.⁵

• Consider prescribing a topical anaesthetic:⁶

  • For adults with extreme pain - eg, 1-2 ml of lidocaine applied as required before passing a stool.

  • Use for a maximum of 14 days.

Referral²

• Refer children with an anal fissure which has not healed within two weeks, consider this earlier if the child is in a lot of pain.

• Refer adults with ongoing pain which has not resolved within 6-8 weeks.

• Consider referring adults with recurrent fissures if they have adhered to management.

• Refer adults who do not have symptoms but whose anal fissure is still present after 12-16 weeks.

• Consider referral in the elderly, as it is a less common condition in this age group and there is a higher likelihood of malignancy. Enquire about symptoms that may suggest colorectal or anal cancer, such as change in bowel habit or iron deficiency anaemia. .

Secondary care management: medical

In secondary care, further medical treatment options which may be used are:

• Topical diltiazem 2%:

  • Calcium-channel blocker causing vasodilation and smooth muscle relaxation.

  • Trials show equal efficacy to GTN but with less risk of headache and fissure recurrence.⁷

  • Chronic anal fissure is an unlicensed indication for diltiazem in the UK, which may be considered before surgery.⁸

• Nifedipine:

  • Also a calcium-channel blocker.

  • Has been studied both orally and topically and shown to have similar efficacy to GTN or diltiazem. However, it is not available in the UK topically and oral treatment (unlicensed) is associated with more side-effects.

• Botulinum toxin:⁹

  • Similar healing rate to GTN but more expensive.

  • Recurrence rate may be higher than with other options.

  • There may be temporary incontinence of flatus and occasionally faeces as a side-effect.

  • Currently an unlicensed treatment in the UK for this indication.¹⁰

• Others with potential promise according to the latest Cochrane review are sildenafil and clove oil but further studies are needed.¹¹

Secondary treatment: surgery

Surgery aims to lower resting anal tone, therefore improving blood supply and thus enhancing healing. Options include:

• Lateral internal sphincterotomy:¹²

  • Procedure of choice.¹³

  • Shown to be more effective than medical management, with an up to 85% cure rate.

  • Significant continence issues may follow, with up to 30% having incontinence of flatus, 20% soiling and 3-10% episodes of leakage. Therefore, this is reserved for those in whom medical intervention has failed.

  • Open or closed approaches appear to be equally effective.

• Posterior internal sphincterotomy

• Bilateral internal sphincterotomy. Further research is needed into efficacy.

• Anterior levatorplasty

• Fissurectomy - may be used in association with botulinum toxin injection. The skin tag is removed along with the fibrotic edges of the fissure.

• Manual anal stretch. The Cochrane review recommends this procedure be abandoned for the management of chronic anal fissure.

Surgery is rarely indicated in children, who normally respond to conservative measures or, failing that, topical agents used in secondary care.

Prognosis²

• Most acute anal fissures heal within two weeks with conservative management, although some may take 6-8 weeks.

• Recurrence is common and may occur in up to half of those treated with topical GTN.

• However, about one half of all patients with anal fissures heal with non-operative management such as high-fibre diet, warm baths and pharmacological treatments.

• In children, early referral is advised if there is non-healing after two weeks. This is because of the risk of the cycle of stool withholding causing constipation, causing worsening of fissures and pain.

• The prognosis in secondary fissures depends upon the underlying pathology.

• For chronic anal fissures, the prognosis following lateral internal sphincterotomy is excellent, with a high cure rate and low risk of recurrence. However, the risk of long-term continence issues is significant.