Fissure-in-ano is a common disorder, characterized by exquisite pain (proctalgia) during and following defecation. It results from a longitudinal tear in the squamous epithelium of the anal canal, frequently precipitated by the passage of a constipated stool, although, in a small proportion of patients, it may follow an episode of diarrhoea. The disorder is more common in males and has a peak incidence in the second decade in females and the third decade in males, although it may also occur in infancy and in old age. In 75 to 94 per cent of cases the fissure is situated at the posterior anal margin: anterior fissures are more commonly encountered in women and may follow parturition or gynaecological procedures. Fissure may coexist with haemorrhoids (Fig. 1) 1162.

Acute anal fissures are superficial and are not normally associated with skin tag formation. Chronic anal fissure is associated with the development of both anal tags and polyps as a result of inflammatory oedema. Chronic subepithelial infection at the fissure results in fibrosis and, in rare instances, anal stenosis. The torn edges of the anal epithelium become undermined and the ulcer deepens, exposing fibres of the internal sphincter muscle. A vicious cycle ensues (Fig. 2) 1163 in which subepithelial inflammation causes spasm of the internal sphincter, inhibiting free drainage of the infected fissure and permitting continued inflammation, resulting in a small, chronic, inadequately drained abscess. The reflex relaxation of the internal sphincter that normally follows defecation is lost in patients with anal fissure; instead contraction of the internal sphincter occurs.

Pain during and shortly after defecation occurs in 73 to 100 per cent of patients; bright rectal bleeding is seen in between 75 and 100 per cent of cases and mucous anal discharge and pruritus ani are also common. The clinical history of chronic anal fissure is typically cyclical; periods of acute pain are followed by temporary healing, only to be succeeded by further acute pain.

The patient should be examined in the left lateral position. Visual examination may disclose a posterior oedematous tag and, on parting the buttocks, an associated fissure may be seen. Discomfort may be severe enough to prevent a digital rectal examination being performed. At some stage in the patient's treatment sigmoidoscopy should be undertaken, under anaesthesia if necessary, to exclude specific causes of fissure, including inflammatory bowel disease (especially Crohn's disease), anal syphilis, anal herpes, anal carcinoma, lymphoma, anoreceptive intercourse (with or without HIV infection), and, in children, sexual abuse.

The principle of management is to break the vicious cycle, thus allowing the fissure to heal by reducing internal anal sphincter spasm.

Acute fissures may heal following alteration of stool consistency. Warm sitz baths and dietary bran produce better symptomatic relief than either hydrocortisone cream or lignocaine gel applied locally in patients suffering from a first attack of posterior anal fissure. Continued consumption of unprocessed bran (15 g/day) may also reduce the recurrence rate. Healing rates of 80 per cent have been reported following 3 weeks' treatment with Proctosedyl ointment (cinchocaine anaesthetic 0.5 per cent and hydrocortisone 0.5 per cent).

The need for regular use of an anal dilator and local anaesthetic gel is debatable. Although this regimen has produced healing rates of 54 per cent, other studies were unable to demonstrate any improvement in the healing of anal fissures when a dilator was used in addition to locally applied lignocaine gel. The presence of anal tags and polyps has been cited as contraindication to conservative therapy since there is a high rate of referral to surgery in these patients.

If an anal dilator is to be used the surgeon must ensure that the patient can demonstrate understanding of its use. The patient is instructed to smear local anaesthetic ointment on to the dilator, to lie on the left side and to insert the dilator up to its hilt, whilst retaining hold of the dilator. The dilator should be kept in this position for 30 to 60 s, removed, and washed in soapy water. The procedure should be performed twice daily.

Surgical management aims to reduce internal sphincter spasm either by maximal anal dilatation or by internal sphincterotomy.

This procedure was first suggested by Recamier in 1838, but became popular following its use by Lord in 1968. It may be performed under local or general anaesthesia. Maximal anal dilatation produces immediate relief from proctalgia in between 75 and 95 per cent of patients, but the recurrence rate is around 10 per cent. Early postoperative complications include bleeding and prolapsing haemorrhoids, and there may be a temporary impairment of control of flatus and faecal soiling.

This operation was first described by Eisenhammer, who divided the sphincter in the posterior position. The recurrence rate following posterior sphincterotomy and fissurectomy is equal to that following lateral sphincterotomy, but the time taken for the wound to heal is double that of lateral sphincterotomy and there is also a greater incidence of postoperative faecal soiling, which is reported to occur in around 25 per cent of patients following posterior sphincterotomy.

Parkes described open lateral sphincterotomy in 1967. Postoperative pain and incontinence are less common following this procedure than after posterior sphincterotomy. The procedure was modified by Notaras in 1969, who described the technique of lateral subcutaneous sphincterotomy: this produces immediate relief of proctalgia in 90 to 100 per cent of patients, healing of the fissure within 2 to 4 weeks in 80 to 98 per cent, and fissure recurs in less than 5 per cent. The operation may be performed under local or general anaesthesia, but better results are obtained when general anaesthesia is used.

Lateral subcutaneous sphincterotomy causes temporary impairment of control of flatus in no more than 10 per cent of patients, while faecal soiling occurs in less than 7 per cent. Three randomized prospective studies comparing anal dilatation and lateral subcutaneous sphincterotomy have demonstrated markedly superior results following the surgical procedure.

No special preoperative preparation is required and surgery may be undertaken as a day-case procedure under general anaesthesia. The patient is placed in the lithotomy position; 15° of head down tilt is advantageous and the perianal area is shaved. Digital and sigmoidoscopic examination is undertaken if it has not previously been performed.

A lubricated anal retractor (of the Eisenhammer or Park's variety) is inserted into the anal canal and the blades positioned to allow exposure of the anal canal in the lateral (3 or 9 o'clock) position. The groove between the internal and external sphincter muscles can readily be palpated when the retractor is opened (Fig. 3) 1164. If desired, 5 to 10 ml of 1 per cent xylocaine and adrenaline (1/200000) solution may be infiltrated into the intersphincteric and submucous spaces (Fig. 4) 1165. Using a size 15 scalpel blade a 0.5 to 1 cm radial incision is made in the lateral position over the internal sphincter, exposing the distal edges of the internal and external sphincter muscles (Fig. 5) 1166. Holding the medial end of the incised epithelium with forceps, the blades of the dissecting forceps (McIndoe's or Lahey type) are passed into the submucosal space and the handles parted to open up the space. The blades of the scissors are then reinserted into the space between the internal and external sphincter muscles and the handles parted to open up this plane (Fig. 6) 1167. The scissors are then withdrawn and introduced with the blades parted, one to lie in the intersphincteric space, the other to lie in the submucous space. The index finger of the left hand of the operator is inserted into the anal canal, the finger tip being placed at the level of the dentate line, and the scissor handles closed to divide the internal sphincter muscle from this point distally (Fig. 7) 1168. Associated tags and polyps can be excised. A dry gauze dressing is placed over the wound. Stool softeners and bulking agents should be administered from 48 h preoperatively and during the postoperative period and mild oral analgesia may be necessary for 24 to 48 h postoperatively, when slight perianal bruising may be observed.

Acute fissure-in-ano in children usually responds to treatment with stool softeners (lactulose), bulking agents, and locally applied anaesthetic ointment. In rare instances, gentle anal dilatation with Hegar's dilators or lateral sphincterotomy may be required. It is important to remember that painful diarrhoea in children may be the presenting symptom of anal fissure, since proctalgia may result in faecal retention and spurious diarrhoea.

Fissure-in-ano may account for 26 per cent of new referrals for patients with Crohn's disease. Medical treatment of the disease usually results in healing of the fissure, as does surgical excision of intestinal Crohn's disease. Extreme caution is advised when undertaking local anal surgery: examination under anaesthesia and drainage of local sepsis may be all that is necessary to relieve symptoms. Sphincterotomy is extremely hazardous since this may be followed by widespread pelvic sepsis and fistula formation.

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