Surgery for Anal Fissure

An anal fissure is a tear of the squamous epithelium that usually extends from the dentate line to the anal verge. In 90% of cases, the fissure manifests as a painful linear ulcer lying in the posterior midline of the anal canal. The fissure may occur in other areas as well, such as the anterior midline (more commonly in female patients), or laterally. Lateral or multiple fissures are considered to be atypical, and should warrant investigation for HIV infection, Crohn disease, syphilis, tuberculosis, or hematologic malignancies.

Patients describe the pain of anal fissures as feeling like "passing broken glass," and they commonly mention a burning pain that can remain for several hours after defecation. ^[1] Many patients report having a lower quality of life because of the pain. ^[2] Bleeding can be an associated symptom that sometimes leads to the misdiagnosis of symptomatic hemorrhoids. ^[3]

The exact cause of anal fissures is currently unknown. Historically, an anal fissure was thought to be a result of mechanical trauma caused by a hard stool tearing the anoderm as it was passed. ^[4] In addition, anal fissures have been associated with increased anal tone for many years. ^[5]  A proposed mechanism for increased anal tone in a study by Lund showed reduced nitric oxide (NO) synthase and, consequently, decreased nitric oxide synthesis in the internal sphincters of patients with anal fissures as compared with control subjects. ^[6] NO has been known to facilitate smooth-muscle relaxation of the internal anal sphincter. ^[7]

Schouten et al proposed that anal fissures were ischemic ulcers and found that patients with anal fissures had significantly higher resting anal sphincter tone and decreased anodermal blood flow in comparison with healthy volunteers. ^[8] Other studies confirmed that blood supply to the posterior midline of the anodermis is relatively poor when compared with blood supply to the other quadrants. ^{[9, 10]}

This combination of increased tone and poor blood supply likely contributes to the relative ischemia of the posterior midline of the anoderm; however, not all patients with anal fissures have anal sphincter hypertrophy or insufficient blood supply to the anoderm.

Pearls

Proctosigmoidoscopy may be performed prior to the procedure to fully inspect the colon, rectum, and anus to rule out concomitant pathology.

It should be kept in mind that the fissure itself does not necessarily require treatment.

Indications for sphincterotomy include the following:

• Chronic anal fissures
• Midline fissures complicated by underlying fistula
• Fissures associated with increased sphincter tone

Treatment of anal fissures is divided into two categories: nonsurgical and surgical. Nonsurgical treatment is considered first-line therapy and includes modalities such as the following:

• High-fiber diets
• Stool softeners
• Warm sitz baths
• Topical analgesics/anesthetics
• Chemical sphincterotomy

It is estimated that half of all patients with an acute anal fissure will have resolution of their symptoms with nonsurgical treatment. ^[11]

When nonsurgical methods fail to heal the anal fissures or relieve symptoms, however, surgical treatment may be necessary. The surgical treatment options are as follows:

• Lateral internal sphincterotomy
• Fissurectomy
• V-Y advancement flap

Although fissurectomy is still performed by some surgeons, the authors do not recommend it, because patients may end up with keyhole deformities. Two randomized trials found that lateral internal sphincterotomy had superior healing rates when compared with fissurectomy.

The V-Y advancement flap is a sphincter-preserving surgical approach for anal fissures. Retrospective results show decreased rates of incontinence with a V-Y flap as compared with lateral internal sphincterotomy, but more prospective data are needed in order to define the role of the V-Y flap in the treatment of anal fissures.  

Lateral internal sphincterotomy is currently the procedure of choice for surgical treatment of chronic anal fissures. ^[3]  It is indicated in the presence of persistent pain, bleeding, and lack of response to medical management. ^{[12, 13]} More than 90% of fissures heal after lateral internal sphincterotomy. The incidence of recurrence is lower with this procedure than with other available options, including fissurectomy and botulinum injection. Insufficient internal anal sphincterotomy is the most common reason for a nonhealing fissure after treatment.

Fissures associated with decreased sphincter tone are a contraindication for surgical treatment.

Anatomy

The anal canal is the most terminal part of the lower gastrointestinal (GI) tract, or large intestine. It lies between the anal verge (anal orifice, anus) in the perineum below and the rectum above. The perianal skin is keratinized, stratified squamous epithelium with skin appendages (eg, hair, sweat glands, sebaceous glands, somatic nerve endings that are sensitive to pain).

The anatomic anal canal skin (anoderm) is also keratinized, stratified squamous epithelium; it has somatic nerve endings that are sensitive to pain, but without skin appendages. The surgical anal canal mucosa is cuboidal in the transition zone and columnar above this zone; it is insensitive to pain. The rectal mucosa above the anorectal ring is lined by pinkish red, insensitive columnar epithelium. For more information about the relevant anatomy, see Anal Canal Anatomy.