Anal Fissure

1.    Definition and Clinical Features

Anal fissure is a painful linear ulcer situated in the anal canal and extends from just below the dentate line to the margin of the anus. It has a similar incidence in both males and females, and is classically found in the posterior midline. Occasionally it is found in the anterior midline in women.

The most widely accepted theory of its pathogenesis is that it results from the mechanical forces imposed on the anal canal during the passage of stool. Hard stool is most commonly implicated, although diarrhoea may also be associated.

Anal fissures are divided clinically into acute and chronic. The definition of chronicity is arbitrary, with chronic or recurrent fissures representing those that recur or fail to heal within 6–8 weeks.

The majority of acute anal fissures heal with simple conservative measures and are often treated by primary care physicians. Chronic anal fissures tend to be refractory to simple conservative measures and require a more aggressive approach to achieve healing. Clinically chronic anal fissure have several easily identified stigmata including hypertrophied anal papilla, indurated edge, internal anal sphincter fibers or granulation tissue at the base, and a sentinel pile.

Most acute anal fissures heal spontaneously or with conservative treatment. Some go on to become chronic and develop secondary changes forming a fibrous skin tag, often referred to as sentinel pile, as well as hypertrophied anal papillae and relative anal stenosis due to scarring. Anal hypertonicity and decreased blood flow to the anoderm, as well as constipation, is thought to contribute to the pathogenesis.

2.    Management

Multiple strategies have been employed to promote the healing of anal fissures. In the setting of acute fissure healing can be expected with conservative management (sitz baths and fiber supplementation) to occur in about half of all patients. However, recurrence rates are high, with several studies reporting recurrence rates of 18% to 27% over long-term follow-up. Once fissure recurrence or chronicity develops, several modalities, both medical and surgical, have been employed to promote healing.

2.1.    Medical Management

2.1.1.    Nitrates

Nitric oxide donors were in the first topical medical treatment applied to chronic anal fissure in order to promote healing. Nitric oxide is the main chemical neurotransmitter involved in mediating relaxation of the internal anal sphincter (IAS) leading to decreased resting and pressures.

Several uncontrolled reports have demonstrated high rates of primary healing with the use of topical nitrates for chronic anal fissure. Healing rates as high as 70% to 80% are demonstrated in several case-controlled trials. Similarly, in a prospective trial Lund and Scholefield demonstrated that a clear advantage was seen for healing of chronic recurrent anal fissures following nitrate therapy.

They demonstrated that nitrate therapy also increased anodermal blood flow and significantly reduced maximal resting anal pressures, countering the pathophysiologic mechanisms of chronic anal fissure.

Several randomized controlled trials have also been completed that found improved healing of anal fissure with topical nitrate ointments. In these studies primary healing rates ranged from 46% to 85%, with recurrence rates ranging from 0% to 43%. Headache Opens in new window, the major side effect of topical nitrates occurred in 8% to 65% of patients undergoing therapy, significantly higher than in placebo controls. Within this group of randomized studies, no episodes of lasting incontinence resulted from nitrate treatment.

Other authors have cast some doubt on the efficacy of topical nitrates for the healing of chronic anal fissure. A systematic review by the Cochrane Database found topical nitrates to be marginally better than placebo for healing of chronic fissures, with late recurrence rates reported as high as 50%.

Other recent literature has shown that the severity of side effects may alter compliance of treatment with topical nitrates. In a study by Dorfman et al., only 67% of patients were compliant with the course of therapy, with side effects being the number one cause for terminating treatment. In this group of patients only 55% had resolution of symptoms.

In a similar study in the United Kingdom, 68% had resolution of symptoms but 11% were unable to complete the course of treatment secondary to side effects. Similarly, in a large multicenter trial comparing topical nitrate treatment to sphincterotomy, 84% of nitrate patients developed side effects, a large proportion of which were headache, with severity of side effects leading to 21% of patients being unable to complete therapy. Many authors still consider topical nitrates as the gold standard medical therapy for the management of chronic fissure. The high recurrence rate and severity of side effects that lead to poor compliance, however, have substantial impact on healing rates.

2.1.2.    Calcium Channel Blockers

Calcium channel blockers, like nitrates, also show pharmacologic activity of smooth muscle relaxation. By blocking the influx of calcium ions, calcium channel blockers such as nifedipine and diltiazem have been given both orally and topically to promote healing by relaxation of the internal sphincter in the treatment of chronic anal fissures.

Treatment with oral nifedipine demonstrated a significant drop resting anal pressures, and resulted in healing rates similar to those with topical glycerine trinitrate. Headaches and flushing were common with oral nifedipine and resulted in treatment completion failure rates similar to those seen with nitrates. Oral diltiazem has been used as well, with similar anal resting pressure results and healing rates to those with oral nifedipine, with a less severe side effect profile.

The use of topical nifedipine has also been evaluated. Antroploi et al. demonstrated in a multicenter trial a 30% reduction in maximal resting anal pressure and a corresponding increased healing rate of chronic anal fissures using nifedipine ointment compared to those using lidocaine/hydrocortisone gel (95% vs. 50%).

Several different investigators have also explored diltiazem as a topical treatment for chronic anal fissure. In evaluating topical diltiazem (2% gel) Carapeti et al. demonstrated healing rates of 75%, with 66% of patients remaining symptom free with long-term follow-up. Of those that recurred after initial treatment with diltiazem ointment, six of seven responded to repeated treatment with healing.

In a randomized controlled trial of oral diltiazem compared to topical treatment, healing rates were twice as high in the topical treatment arm (65% vs. 38%), suggesting that local therapy is more efficacious than systemic treatment. Side effects were seen to be less in the oral calcium channel blocker group than previous published results for nitrates, and the topical diltiazem group had the least complaints of detrimental side effects.

In two randomized controlled trails directly comparing topical diltiazem gel and nitrates, healing rates were similar with a significant difference in side effect profiles favoring diltiazem.

Based on the data available, calcium channel blockers, particularly diltiazem, is at least as effective as nitrates in promoting healing of chronic anal fissures with a much more favorable side-effect profile. Most authors conclude that diltiazem should be used either as a second-line treatment for those who have failed topical nitrates or recur following nitrate treatment, or as a first-line treatment of chronic anal fissure.

2.1.3.    Fissurectomy

In the setting of recurrent anal fissures for which maximal medical management has been tried and failure to heal occurs with lateral internal sphincterotomy, two major surgical alternatives remain: fissurectomy and anal advancement flaps.

Given the concerns of increased incontinence rates with repeated sphincterotomy, sphincter-preserving alternatives have been investigated. Fissurectomy entails excision of the chronic granulation tissue, hypertrophied papilla, and scar, and is either left open or closed primarily.

Engle et al. looked at the combination of fissurectomy with nitrate topical therapy in 17 patients with chronic recurrent fissures. The majority of patients had not undergone previous sphincterotomy. All of the chronic fissures had healing following 10 weeks of follow-up. Similarly, Lindsey et al. looked at the combination of fissurectomy and botulinum toxin injection in those failing medical management.

Healing occurred in 93% of patients who had complete healing with median follow-up of 16.4 months. Despite concerns with a keyhole deformity possibly occurring following fissurectomy, in both studies the incontinence rates were only as high as 7%, which was transitory to flatus only.

In a similar study looking at the use of botulinum toxin in the setting of fissurectomy with a mean follow-up of 1 year, fissure healing rates were found to be 79%, with only four patients with recurrence identified, but no comments were made on them. No literature exists on fissurectomy alone for the treatment of chronic or recurrent anal fissure.

While fissurectomy in combination with either nitrates of botulinum toxin appears to be viable alternative to lateral internal sphincterotomy, the majority of authors still recommend lateral internal sphincterotomy over fissurectomy. Fissurectomy may be an alternative method for those who have failed following lateral internal sphincterotomy, or where excessive anxiety about division of the internal anal sphincter precludes lateral internal sphincterotomy.

2.1.4.    Anal Advancement Flaps

An alternative method for sphincter preservation in the setting of chronic or recurrent anal fissure is advancement flaps. Anal advancement flaps are advantageous in those with an already increased risk of incontinence, such as the elderly, diabetics, multiparous women, and those who have already undergone sphincterotomy unsuccessfully.

The goal of advancement flaps is to replace chronic nonhealing granulation tissue with well-vascularized tissue with a better chance to heal. Kenefic et al., in a group of patients who had undergone multiple surgical attempts at fissure healing, found a high rate of complete healing with advancement anoplasty.

Similarly Nyam et al. demonstrated healing of anal fissures in patients who were poor candidates for sphincterotomy givne hypotonia of the internal anal sphincter preoperatively. In this group of 21 patients, no significant complications and most importantly no alterations in continence were observed over a follow-up of 18 months.

Singh et al. proposed rotational flaps to treat chronic and recurrent anal fissure in an attempt to limit the complications observed at flap donor sites. In this series of 21 patients, 17 had complete resolution of symptoms, with only three patients having recurrence of their fissure.

Summary

Anal fissure is a common and distressing problem. Acute fissures require minimal treatment, and in most instances will heal spontaneously with mild conservative measures. Chronic anal fissure or recurrent anal fissure is treated with various medical and surgical treatments. Although medical management is attractive because of limited side effects and minimal risk of incontinence, healing rates remain moderate.

Surgical interventions with a tailored lateral internal sphincterotomy remains the gold standard in promotion of healing for chronic anal fissure. Those with sphincter weakness or who are at increased risk of incontinence have reasonable results with advancement flap techniques that spare the internal sphincter muscle. The optimal management of chronic fissure based on patient satisfaction and cost-effective treatment is still debated in the literature.