- Author: Vassiliki L Tsikitis, MD; Chief Editor: Kurt E Roberts, MD more...
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). Patients describe the pain of anal fissures as "passing broken glass" and a burning pain that can remain for several hours after defecation. Many patients report a lower quality of life because of the pain.
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. In addition, anal fissures have been associated with increased anal tone for many years.
A proposed mechanism for increased anal tone in a study by Lund showed reduced nitric oxide synthase and, therefore, decreased nitric oxide synthesis in the internal sphincters of patients with anal fissures when compared to control subjects. Nitric oxide has been known to facilitate smooth muscle relaxation of the internal anal sphincter.
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 when compared to healthy volunteers. Other studies have confirmed that blood supply to the posterior midline of the anodermis is relatively poor when compared to that of the other quadrants.[8, 9]
This combination of increased tone and poor blood supply likely contribute to the relative ischemia of the posterior midline of the anoderm; not all patients with anal fissures, however, have anal sphincter hypertrophy or insufficient blood supply to the anoderm.
Treatment of anal fissures is divided into two groups: nonsurgical and surgical. Nonsurgical treatment is considered first-line therapy and includes such modalities as high-fiber diets, stool softeners, warm sitz baths, topical analgesics/anesthetics, and chemical sphincterotomy.
When nonsurgical methods fail to heal the anal fissures or relieve symptoms, however, surgical treatment may be necessary. The surgical treatment options are lateral internal sphincterotomy, fissurectomy, and V-Y advancement flap. Fissurectomy is still used by some surgeons; however, the authors do not recommend fissurectomy, because patients may end up with keyhole deformities.
Lateral internal sphincterotomy is the current procedure of choice for surgical treatment of chronic anal fissures. Performance of lateral internal sphincterotomy is indicated in the presence of persistent pain, bleeding, and lack of response to medical management.[11, 12] 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.
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 and has somatic nerve endings (sensitive to pain), but without skin appendages. The (surgical) anal canal mucosa is cuboidal in the transition zone and columnar above it; 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.
There is a great deal of controversy regarding the use of botulinum toxin for the treatment of anal fissures. Injection of this toxin is typically used for chronic anal fissures that have failed to improve with medical management. Additionally, there may be a role for it in the management of recurrent anal fissure following lateral internal sphincterotomy.
Published techniques involve injection dosages that range from 10 to 100 units. Healing rates have varied in the literature, from 67.5% to over 90%, according to the most recent Cochrane review. Recurrence rates after botulinum toxin treatment are high and range from 40% to over 50% at 1 year. Incontinence to flatus is common after the procedure; however, this spontaneously resolves in all patients.
The authors typically use 100 units of onabotulinumtoxinA (Botox), injecting 40 units in both the right and the left intersphincteric groove, along with 10 units in both the anterior and the posterior anal canal. Patients are continued on stool softeners and a topical calcium channel blocker for eight weeks. Success rates are in the 90th percentile; failure of this treatment has been noted, especially in patients with longstanding chronic anal fissures.
Equipment employed in an anal fissurectomy includes the following:
Pratt bivalve speculum
Suture, 3-0 chromic catgut
Position the patient as described above. Prepare the surgical field with povidone-iodine (Betadine) or chlorhexidine solution. Drape the field so that the visual field includes the anus. Administer local anesthetic as described above. Inspect the anoderm and anus using an anoscope.
Insert a Pratt bivalve speculum to evaluate the anal pathology. Rotate the Pratt bivalve speculum to the right or left lateral position.
Make a linear incision with a scalpel from the dentate line to just beyond the anal verge. Carry out the dissection until the internal sphincter and a few fibers of the external sphincter are exposed (see the image below).
Achieve hemostasis with electrocautery. Under direct vision, divide the full thickness of the internal sphincter from the level of the dentate line distally (see the image below). Littlejohn and Newstead reported good results in a retrospective study with tailored sphincterotomy — that is, division of the internal anal sphincter for the length of the fissure rather than the dentate line. The authors recommend tailored sphincterotomy.
Close the incision with a 3-0 chromic catgut suture in a running fashion (see the image below). If preferred, the incision may be left open.
Another option is to perform a closed lateral internal sphincterotomy, in which a “blind” lateral subcutaneous internal anal sphincterotomy is performed with a No. 11 blade scalpel after the intersphincteric groove has been located via manual palpation (see the image below).
Studies have found no evidence of a significant difference in results between the open and closed techniques. However, the closed technique requires experienced knowledge of anorectal anatomy and should be reserved for surgeons with advanced colorectal training.
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.
Possible complications of anal fissurectomy include the following:
Hemorrhoidal tissue prolapse
Indications and Contraindications
Indications for fissurectomy include the following:
Chronic anal fissures
Midline fissures complicated by underlying fistula
Fissures associated with increased sphincter tone
Fissures associated with decreased sphincter tone are a contraindication.
Anesthesia and Positioning
The procedure is typically done with local anesthesia using 0.5% bupivacaine with epinephrine 1:100,000. General anesthesia may be required for difficult cases or for anxious or uncooperative patients.
The patient is placed in a prone jack-knife position with the buttocks strapped apart.
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