House, Diamond, V-Y

James W. Fleshman

Ira J. Kodner

Indications/Contraindications

Flaps can be used to cover defects in the perianal skin after excision of anal lesions such as Paget’s disease or Bowen’s disease. Stricturing will sometimes result from iatrogenic or idiopathic causes and are treated with advancement of extra skin into the anal canal. The use of flaps to bring normal inner buttock skin toward or into the anal canal can relieve the stricturing from the scar or lack of skin but will not impact the narrowing caused by a hypertrophied internal sphincter. Ectropion is the exposure of anal canal or low rectal mucosa at the level of the anal verge caused by previous resection and causes a large amount of mucous production and even bleeding. Readvancement of the mucosa back into the anal canal and replacement of the defect with inner buttock skin is the preferred method of treating the ectropion.

Consideration should be given to the etiology of the stricture prior to recommending skin flap advancement. Crohn’s disease has very limited indications since the healing process is impaired. Radiation-induced stricturing most likely involves damage to the perianal skin and may also have some skin buttock impairment. The most common cause for anal stricturing is an over zealous hemorrhoidectomy with removal of more viable anoderm than is adequate to dilate the anal canal. Replacement of this anoderm with skin from the inner buttock is the ideal indication for skin flap advancement for treatment of stricture.

The Whitehead hemorrhoidectomy with circumferential excision of the anoderm of the anal canal has resulted in an ectropion and stricture formation in many patients who have been treated with an inappropriately performed Whitehead procedure. The ectropion can be reduced into the anal canal and the stricture treated at the same procedure using a broad-based house-shaped skin flap.

Patients who have no ectropion but have normal external anoderm and normal rectal mucosa but simply have lost dermis at the level of the dentate line benefit most from a diamond-shaped skin advancement flap.

Preoperative Planning

The mobilization of inner buttock skin into the anal canal can be accomplished based on the principles of plastic surgery flap construction. The base of the flap should be broad enough to maintain an adequate blood supply. The dissection should be performed with
as little cautery as possible, and the mobility of the flap toward the anal canal should be maximized by releasing the tethering attachments under the donor site rather than under the flap skin itself.

The patient should undergo a complete bowel preparation and receive preoperative antibiotics. The patient should be informed that a period of low activity without sitting, driving, or climbing steps will be enforced for the 2 weeks after surgery. The consideration for doing a unilateral flap versus bilateral flaps should be made preoperatively and determined by the amount of coverage needed outside and within the anal canal.

Surgery

V, U, or House-Shaped Flap

Positioning

The patient should be placed in the prone-jackknife position with the buttocks taped apart. The perineum is prepped and draped sterilely. Local anesthesia can be obtained with the patient sedated to relax the muscle and provide local anesthetic. Care should be made not to use Epinephrine because of its vasoconstrictive features. The flap should be drawn on the inner aspect of the buttock with a broad-base encompassing approximately the entire side of the anal canal in the case of stricturing. The length of the flap is determined by the base and should be two to three times the length of the base.

Technique