Anal Fissures: Lateral Internal Sphincterotomy

James S. Wu

Perioperative Considerations

An anal fissure is a longitudinal tear in the anoderm of the anal canal that exposes the internal sphincter and allows sphincter spasm when the area is stimulated.

The majority of fissures are located in the midline (posterior > anterior) of the anal slit (Fig. 9-1). Fissures located at lateral locations are atypical and are associated with HIV infection, Crohn disease, syphilis, tuberculosis, and hematologic malignancy.

FIGURE 9-1 ▪ Fissures most commonly occur at the posterior and anterior ends of the anal slit (arrows). (Reprinted with permission, Cleveland Clinic Center for Medical Art & Photography © 2019. All Rights Reserved.)

Acute fissures (present for <8 weeks) appear as a longitudinal tear. Fissures present for >8 weeks are classified as chronic; these may show a “sentinel” skin tag at the distal end of the fissure and exposed internal anal sphincter muscle.
First-line treatment generally is nonoperative and includes warm sitz baths, psyllium fiber, topical anesthetics, topical nitrates, and topical calcium channel blockers. Botulinum toxin injection and balloon dilation are alternate therapies.
Operative treatments include lateral internal sphincterotomy, debridement, and anoplasty.

Examination

Gentle lateral traction on the perianal skin may demonstrate a “sentinel” pile and fissure.
If a fissure is not seen, gentle palpation of the distal anal canal with a well-lubricated finger confirms the presence of a fissure and its location.
Because the internal anal sphincter is hypertonic and the area of the fissure is tender, anoscopy may not be tolerated and can be omitted if the diagnosis is established without it. Examples of fissure, shown in Figure 9-2, demonstrate a variety of appearances.

FIGURE 9-2 ▪ A. Chronic posterior anal fissure with exposed internal anal sphincter (IAS). B. Chronic anterior anal fissure (arrows) with exposed IAS. C. Three simultaneous posterior and posterolateral anal fissures, arrowheads depict the fissures. D. Acute anal fissure caused by diarrhea during bowel preparation and seen during colonoscopy with narrow-band imaging. E. Simultaneous anterior and posterior anal fissures. (Reprinted with permission, Cleveland Clinic Center for Medical Art & Photography © 2019. All Rights Reserved.)