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Anal fissure: Clinical manifestations, diagnosis, prevention

Elizabeth Breen, MD
Ronald Bleday, MD
Section Editors
Martin Weiser, MD
Lawrence S Friedman, MD
Deputy Editor
Wenliang Chen, MD, PhD


An anal fissure is one of the most common benign anorectal conditions that may result from high anal pressure. Anal fissures may be acute or chronic. Acute fissures may result from local trauma or may be secondary to an underlying medical/surgical condition.


An anal fissure is a tear in the anoderm distal to the dentate line (figure 1) [1]. By definition, an acute anal fissure typically heals within six weeks with conservative local management, while a chronic anal fissure fails conservative management and requires a more aggressive, surgical approach [1-4]. The etiology of the fissure determines if it is primary (eg, local trauma) or secondary (eg, inflammatory bowel disease, malignancy).


An anal fissure is the result of the stretching of the anal mucosa beyond its normal capacity. Once the tear occurs, it begins a cycle leading to repeated injury. The exposed internal sphincter muscle beneath the tear goes into spasm. In addition to causing severe pain, the spasm pulls the edges of the fissure apart, which impairs healing of the wound. The spasm also leads to further tearing of the mucosa with the passage of subsequent bowel movements. This cycle leads to the development of a chronic anal fissure in approximately 40 percent of patients [2].

It has been proposed that ischemia may contribute to the development of an anal fissure. Blood flow in the anoderm at the posterior midline, the site of most fissures, is less than one-half that in other quadrants in the anal canal [5,6]. Furthermore, the rate of perfusion is inversely related to anal pressure and, in one study, patients with chronic anal fissure had higher anal pressures than those with fecal incontinence, hemorrhoids, or other colorectal disorders, or controls [5]. The demonstration of reduced blood flow provided the rationale for the use of topical nitroglycerin in the treatment of this disorder (see "Anal fissure: Medical management", section on 'Topical nitroglycerin').

The elevation in anal pressure in patients with chronic anal fissure may result from increased tone of the internal anal sphincter, which can be demonstrated manometrically [7-9]. In one study, for example, manometry was performed in 12 patients with chronic anal fissure and in 12 controls [7]. The mean average resting pressure of the internal sphincter was significantly higher in patients with a chronic anal fissure (120 versus 83 mmHg).

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Literature review current through: Sep 2017. | This topic last updated: Jun 08, 2015.
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