Anal fissure (tear)
Anal fissure is a superficial tear in the mucosa of the distal anal canal characterised by pain on defaecation, rectal bleeding, and spasm of the anal sphincter. Healing, which is usually uneventful, may be helped by conservative management with bran and bulk laxatives and topical local anaesthetics for pain relief. Surgical treatment has been used for patients who develop a chronic condition but has been associated with high rates of long-term incontinence and recurrence.
Although a systematic review considered that surgery was more effective than alternative medical therapies, a number of these have been investigated. As hypertonicity of the internal anal sphincter may be involved in the pathophysiology of chronic anal fissure, local injections of botulinum A toxin have been used to produce paresis of this sphincter.
The duration of the effect appears to be long enough to allow complete healing of the fissure in most patients although some may relapse; a long-term, follow-up trial involving 57 completely healed patients, noted a high recurrence rate (41.5%) once the effects of botulinum toxin disappeared. Temporary incontinence had been the only adverse effect reported during treatment.
Topical application of nitrates can relax the anal sphincter; numerous studies have reported benefit from topical application of glyceryl trinitrate, although a high rate of spontaneous resolution with placebo has cast doubt over the degree of advantage in some studies. Follow-up10 of patients treated with glyceryl trinitrate indicated that after 24 to 38 months most had not experienced further problems or had had occasional recurrences which in the majority of cases had responded to further topical treatment. Isosorbide dinitrate ointment has also been tried, and may be of benefit with botulinum A toxin.
Beneficial responses to diltiazem reported in 2 patients with proctalgia fugax may have been due to smooth muscle relaxation. The resting pressure of the internal anal sphincter was decreased by a mean of 20.6% in all but 1 of 13 subjects given a single 60-mg oral dose of diltiazem. A small study has compared oral with topical diltiazem in the management of anal fissure. Despite a higher response rate with the topical drug, no significant difference in benefit was seen between the 2 routes. A subsequent study suggested topical diltiazem (2%) might be of benefit in patients with anal fissure unresponsive to topical nitrates.