Fissure in Ano

Anal Fissure

Gastroenterology > Anal Fissure

Key points

• Anal fissure, also known as fissure in ano, is a linear tear in the lining of the distal anal canal below the dentate line
• The majority of anal fissures are idiopathic in nature
• The classic symptoms are severe anal pain, described as tearing, cutting, or burning, during or after defecation, sometimes accompanied by the passage of bright red blood per anus
• Anal fissure is one of the most common lesions to consider in the diagnosis of anal pain
• The diagnosis is established on the basis of a thorough history and inspection of the anal canal
• Conservative treatment, including laxatives, dietary modifications, and sitz baths, is safe, has few adverse effects, and should be considered first-line therapy for acute anal fissures
• Surgery, particularly lateral internal sphincterotomy, is the treatment of choice for treatment-resistant and refractory anal fissures

Background

Description

• Anal fissure may be related to poor circulation in the posterior midline of the anal canal, where more than 90% of fissures occur
• When a hard stool that tears the anal skin is passed, there is not sufficient blood supply to heal the split in the skin
• Alternatively, the skin in the posterior midline breaks down with more minimal trauma and cannot heal
• All treatments are aimed at reducing the spasm of the internal anal sphincter, which increases local blood flow and leads to the relief of symptoms and healing of the fissure

Epidemiology

• The true prevalence of anal fissures is unknown, but it is estimated that they account for 6% to 15% of proctology referrals
• Anal fissures occur mostly between the second and fourth decades of life and affect men and women equally

Causes and risk factors

Causes:

• The majority of anal fissures are idiopathic, with no identifiable underlying disease process
• Traditionally, the etiology is believed to be traumatization of the anal mucosa by the passage of hard stool, but this does not explain why only 25% of patients report constipation and why the onset of symptoms follows a bout of diarrhea in 4% to 7% of cases
• Patients with chronic anal fissures generally have increased resting anal pressures caused by hypertonicity of the internal anal sphincter, but the causative mechanisms are unclear. Elevated anal pressure also exacerbates the ischemic state of the posterior commissure and the sphincter and reduces anodermal blood flow
• Angiography of the inferior rectal vessels has shown a scarcity of arterioles at the posterior commissure of the anal canal, the site for which fissures appear to have a predilection, in 85% of cases. It is possible that blood vessels traversing the hypertonic internal sphincter en route to the anal mucosa may be compressed, resulting in compromised perfusion of the anal mucosa and fissure
• Histologic examination of biopsy specimens obtained from the base of chronic fissures in the internal anal sphincter and at sites remote from it has shown fibrosis in all regions, leading to the hypothesis of an underlying inflammatory process in which myositis occurs early on, with subsequent fibrosis, which may be secondary to ischemia

Risk factors:

• Trauma, resulting from hard bowel movements, diarrhea, anal instrumentation, or childbirth, may be the initial cause of anal fissures. Women who develop symptoms postpartum account for 11% of all patients with anal fissures. The risk increases with traumatic deliveries, and the fissures are commonly in the anterior midline. Shearing forces from the fetal head on the anal mucosa may be significant in this patient population. Postpartum, the anal mucosa may become tethered to the underlying muscle, rendering it more susceptible to trauma
• Low fiber intake
• Psychological stress produces a sustained tonic rise in anal canal pressure and may be one factor in the etiology of anal fissures

Screening

To date, there are no guidelines recommending routine screening for anal fissures in asymptomatic patients.

Primary prevention

Summary approach

Although there is no direct evidence that preventive measures affect outcome, prevention of constipation through dietary modifications may be helpful.

Population at risk

• Persons with low dietary fiber intake
• Persons with a sedentary lifestyle
• Postpartum women
• Persons with significant stress or anxiety

Preventive measures

• The optimum method of improving colonic function to prevent constipation is to prescribe a diet high in fiber. The amount of fiber that is necessary to correct constipation varies from person to person, but the effect of fiber on stool weight is dose dependent
  • The 2005 Dietary Guidelines for Americans, produced by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, support a daily fiber intake of 14 g per 1,000 kcal (average of 20-25 g/d) to promote healthy laxation, for a critical daily stool weight of 160 to 200 g. This not only prevents constipation but also reduces the risk of cardiovascular disease
  • 'Dietary fiber' is defined as nondigestible carbohydrates and lignins that are intrinsic and intact in plants. Foods high in dietary fiber include whole grains, legumes, vegetables, and fruits. Another class of fiber known as 'functional fiber' refers to nondigestible carbohydrates extracted from foods that have beneficial physiologic effects in humans. Intake of dietary fiber, mainly insoluble fiber, increases stool bulk and frequency and decreases stool consistency in healthy people. Most vegetables are approximately 30% to 40% soluble fiber and 60% to 70% insoluble fiber. Most legumes average 10% to 25% soluble fiber and 75% to 90% insoluble fiber. Fruits vary from 30% to 65% soluble fiber and 35% to 70% insoluble fiber
  • Nondigestible or resistant starch and oligosaccharides, such as fructo-oligosaccharides, cannot be decomposed by human digestive enzymes in the upper digestive tract and, thus, are included in the nutritional/physiologic definition of functional fiber. The most important sources of fructo-oligosaccharides include garlic, Jerusalem artichokes, chicory, leeks, onion, wheat, asparagus, and artichokes. Resistant starch can be found in potato (raw and cooked), banana, bread, cornflakes, and partly milled grains and seeds
• The need to set aside a regular time for defecation and respond to defecatory urges should be emphasized
• Patients should be encouraged to increase fluid intake to 1.5 to 2 L/d to increase stool frequency
• Exercise is recommended to prevent constipation, as physical activity affects colonic motor function, with functional changes proportional to the extent of activity