The patient is placed in a prone jackknife position. This position allows the surgical team full access to the operative field. Retracting 3-in. silk tape that has been placed on the buttocks and securing it to the sides of the operating table provides exposure. Lithotomy and a left lateral or modified Sims’ positions can also be used.

Although LIS can be performed under general or regional anesthesia, our preference is MAC and a local block. After initially attaining adequate sedation and comfort under MAC, a local block with bupivacaine and epinephrine is used. This block provides analgesia and allows relaxation of the sphincter to facilitate surgery. The vasoconstrictive effects of epinephrine will decrease vascularity during the surgery and increase the period of postoperative analgesia.

Initially, 10 ml of the local anesthetic is injected circumferentially into the perianal skin and the subcutaneous tissue with a 1.5 in. × 25 gauge needle. A circumferential deeper injection into the sphincter is then performed. Typically, a total of 20–30 ml of the local anesthetic is needed to complete the operation.

Whatever anesthesia is selected, patients may benefit from the use of a local block that contains epinephrine in addition to the analgesic/anesthetic. Procedures performed under general anesthesia still benefit from the additional sphincter relaxation and hemostasis attained with the bupivacaine and epinephrine. The vasoconstrictive effects of epinephrine are also helpful in offsetting the vasodilatory effects of a spinal anesthetic.

After appropriate positioning and anesthesia are attained, the presence of a fissure is confirmed with circumferential examination of the anal canal using a Hirschmann anoscope. A 35-mm Hill-Ferguson retractor provides a consistent measure of the diameter of the anal canal. Resistance during insertion of this retractor confirms the presence of a hypertonic/spastic sphincter and a taught, bank-like internal sphincter is seen (Fig. 17.2). Failure to identify a hypertonic sphincter should prompt further evaluation before a sphincterotomy is performed.

Selection of either the left or the right lateral quadrant for the sphincterotomy is contingent upon where the internal sphincter is best noted and whether hemorrhoidal tissue would interfere with the operative field. An incision is made at the intersphincteric
groove and extended 1.5–2.0 cm distally to the perianal skin. A fine, curved hemostat is used to mobilize the anoderm off the internal sphincter up to the level of the dentate line (Fig. 17.3). Caution is used to prevent violation of the anoderm since nonhealing of this may result in a fistula. The intersphincteric plane is accessed and the internal sphincter is isolated with the hemostat up to the dentate (Fig. 17.4). Electrocautery may be used to control small points of bleeding.