Surgery for Chronic Anal Fissure

Explanation

A chronic fissure is defined by symptoms lasting more than six to eight weeks together with the classic triad of a sentinel skin tag, a hypertrophied anal papilla and exposed internal sphincter fibres in the fissure base, all of which reflect long standing sphincter hypertonia. The underlying problem is a vicious cycle of pain, reflex internal sphincter spasm, raised resting anal pressure and reduced perfusion of the posterior commissure, which prevents healing. Definitive surgery must therefore lower resting pressure. Lateral internal sphincterotomy divides a controlled length of the distal internal sphincter away from the fissure, permanently reducing resting anal pressure and restoring blood flow, and it heals more than 90 percent of chronic fissures with a low recurrence rate. It is performed laterally rather than in the midline to avoid a keyhole deformity. The main risk is minor incontinence to flatus, which is why it follows rather than precedes medical treatment. Fissurectomy alone removes the tag and fissure edges but does nothing to the hypertonic sphincter, so healing is unreliable and recurrence common. Anal dilatation is an uncontrolled stretch that tears the sphincter unpredictably and has been abandoned because of unacceptably high rates of permanent incontinence. Division of the external sphincter is anatomically wrong, since that voluntary muscle is essential for continence.

Why each option

A.

Correct. Lateral internal sphincterotomy lowers resting anal pressure, restores perfusion and heals over 90 percent of chronic fissures refractory to medical therapy.

B.

The external sphincter is the voluntary muscle responsible for continence; dividing it would cause major incontinence and does not address internal sphincter hypertonia.

C.

Fissurectomy with tag excision addresses the visible lesion but leaves the hypertonic internal sphincter untreated, so the fissure commonly fails to heal or recurs.

D.

Manual anal dilatation tears the sphincter in an uncontrolled way and has been abandoned because of unacceptably high rates of permanent faecal incontinence.

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