Abdominoperineal resection (APR) refers to the removal of a portion of the left colon, the entire rectum and anus, and creation of an end colostomy. It should be considered when the tumor is invading the anal canal, sphincter complex, or the pelvic floor; if the surgeon can’t get a negative distal-free resection margin in very low rectal tumors; if the patient has fecal incontinence preoperatively; or patient preference. The initial steps of the operation are the same as laparoscopic low anterior resection (LAR) so, in some ways, this chapter is a continuation of the LAR chapter.
In general, ureteral stent placement is preferable in APR. Placing bilateral stents will allow the surgeon to identify the ureters during the pelvic part of the operation. This is important especially if the tumor is bulky and if there is extensive fibrosis in the tissues due to radiation. Occasionally, even with the stents, it’s difficult to identify, and extreme care should be exercised during the pelvic dissection.
Review the pelvic magnetic resonance imaging (MRI) of the patient carefully, because it will provide you with a road map to the operation. There are many useful pieces of information that you need to get from the MRI before you start, which includes:
Location of tumor.
T stage of tumor.
Lymph nodal enlargement (N staging).
Distance of tumor from anorectal ring/sphincter complex.
Involvement of surrounding organs (prostate, seminal vesicles, bladder, ureter, uterus, vagina) or anal sphincters complex.
Relationship of tumor to the line joining the sacral promontory to symphysis pubis. Any tumor below this line is in the true pelvis. Such tumors should be considered for preoperative chemoradiation treatment if they are T3 or higher or have node-positive disease.
In all cancer cases, adequate margins are paramount. For upper rectal cancer, getting adequate margins is not difficult and we aim for a 3–5-cm margin. In mid-to-low rectal cancers, 1–2 cm of negative margin should be ideal but 0.5–1-cm margins are acceptable. However, for sphincter preservation, we perform intraoperative frozen section and aim for negative margins. If the tumor is very low, and a negative margin cannot be achieved, APR should be done. In addition, during the resection of the mesentery, the IMA should be divided at its origin. This maximizes adequate lymph node harvest. Prior to starting the case, carrying out a digital rectal examination is important because this helps make an accurate final clinical assessment of how low the tumor is, especially because the last clinical exam may have been weeks prior to the surgery. In female patients with anterior tumors, we also do a vaginal exam to rule out involvement of the posterior vaginal wall.