Abdominoperineal Resection (APR)

Also known as the Miles procedure. See Total Mesorectal Excision (TME) & Sphincter-Sparing Resection for the sphincter-preserving alternative. Content below is from a textbook reference chapter (Sabiston Ch52 - Rectal Cancer Surgery), not primary literature.

Indications

If the sphincters are infiltrated by tumor, complete excision of both the rectum and the anus, along with the sphincter apparatus, must be performed, together with creation of a permanent colostomy. Also an option for elderly patients with distal rectal cancer and poor sphincter function, since an end colostomy can offer a better quality of life than an ultradistal coloanal anastomosis that would further compromise continence.

Technique

The IMA is divided, the descending colon is mobilized and divided above the rectosigmoid junction, and the rectum is dissected according to TME principles down to the level of the levator ani (see Total Mesorectal Excision (TME) & Sphincter-Sparing Resection for the TME technique itself). The colostomy aperture is created. The perineal part of the operation then begins: a purse-string suture is placed around the anus, and an elliptical incision made around the anus, which is then excised en bloc with the sphincter. Dissection continues cephalad until the abdominal plane of dissection is reached, and the specimen is removed through the pelvic incision. The perineum is closed in layers. The empty pelvis can often be filled with an omental pedicle; wider perineal resections (especially in irradiated pelvises, which have more healing difficulty) may need the perineal defect closed with a rectus abdominis flap or gracilis muscle flap.

The specimen includes the origin of the IMA, the mesorectum, the hemorrhoidal vessels, and the “naked” portion of the ultradistal rectum and anal sphincters.

Recurrence rate and the case for a wider (cylindrical) excision

APR carries an intrinsic risk of higher recurrence rates than low anterior resection — up to 33%. This is partly explained by APR being performed for more aggressive cancers, but there’s also an intrinsic higher risk of specimen perforation and a higher rate of positive circumferential margins (up to 40%) in patients undergoing APR — a technical, not just biological, contributor.

For this reason, a wider excision has been proposed, allowing a more cylindrical resection and avoiding the risk of “coning” toward the rectum (the conventional dissection plane tends to narrow toward the rectum, increasing the risk of a positive margin at the level of the tumor). After the abdominal part of the operation is completed, the patient is rotated to a prone jackknife position; a wider elliptical incision is made up to the tip of the coccyx (removed with the specimen), and the sphincter apparatus is removed en bloc with the levator ani in a cylindrical manner. The wide perineal defect, if needed, can be closed with a biologic mesh or a muscle flap.

Open items / gaps

• No primary trial data yet directly comparing conventional vs. cylindrical APR oncologic outcomes — described here as a proposed solution to the coning/positive-margin problem, not validated with a specific cited study.
• No detail on APR-specific complications (perineal wound issues, sexual/urinary dysfunction rates) beyond what’s covered generally for TME dissection.