Open Abdominoperineal Resection

Wolfgang B. Gaertner

Genevieve B. Melton-Meaux

INDICATIONS/CONTRAINDICATIONS

Abdominoperineal resection (APR) is generally performed for patients who have rectal adenocarcinoma, but it may also be performed for benign conditions such as inflammatory bowel diseases or fecal incontinence and is sometimes appropriate for other anorectal and pelvic malignancies or as a salvage procedure for anal cancer. The technique discussed in this chapter is intended to achieve radical clearance of anorectal malignancies; more conservative techniques of APR used for benign conditions are not discussed here in detail. Both open and minimally invasive approaches are used for APR of rectal cancer and have been proved to be safe. The current role of minimally invasive techniques for proctectomy remains under study. This chapter focuses on the operative technique used during an open approach for APR. The principles and techniques described here are applicable with minor modifications to extended operations for rectal cancer such as en bloc sacrectomy, vaginectomy, or full pelvic exenteration.

The decision whether to perform anterior resection (AR) with colorectal anastomosis versus an APR and permanent colostomy is dependent on oncologic considerations, technical considerations, the surgeon’s operative skills and experience, anticipated functional outcomes, and patients’ desires. Important oncologic and technical considerations include preoperative level of the lesion in the rectum and, in particular, its relationship to the anal sphincter complex and levator ani muscles, pretreatment stage of the cancer including any local organ invasion or distant spread, histology predictors of poor outcome, threatened or involved margins, and the tumor response to neoadjuvant therapy. In general, obesity and the narrow male pelvis add to the technical challenges. Both open APR and AR curative-intent radical resections for rectal cancer use the same total mesorectal excision (TME) technique to mobilize the rectum with its mesorectum and achieve proximal, lateral, and radial margin clearance. Although a 2-cm distal mural margin has traditionally been recommended, a negative distal margin of 5 mm to 1 cm has shown similar oncologic results. Furthermore, a 5-cm distal mesorectal margin becomes impossible for patients undergoing radical resection of distal rectal tumors. The choice of APR versus AR is primarily dependent on the surgeon’s ability to achieve a negative distal mural and mesorectal clearance and perform a reliable sphincter-preserving anastomosis. In general, the more distal the anastomosis is located, the higher the risk of anastomotic complications and poor function. Pelvic radiation also increases the risk of anastomotic problems and worsens functional outcomes. Although patients understandably may prefer a sphincter-preserving proctectomy to APR, they should be informed that sphincter preservation is not uniformly associated with better quality of life. It is generally counterproductive to compromise oncologic
control in a heroic attempt to avoid a permanent colostomy because recurrences and poor functional results are associated with increased rates of cancer recurrence and poor quality of life. The ultimate decision whether to perform a sphincter-preserving proctectomy often relies on the intraoperative evaluation of the tumor once the rectum has been completely mobilized without risking “coning” if an APR is performed.

PREOPERATIVE PLANNING

Assessment and Staging

All patients with a newly diagnosed rectal cancer should undergo full clinical assessment as well as pretreatment staging with full colonoscopy; computed tomography (CT) of the chest, abdomen, and pelvis; magnetic resonance (MR) of the pelvis and a carcinoembryonic antigen level to assess the tumor and search for synchronous lesions and metastatic disease. A full discussion of this topic is beyond the scope of this chapter. A history of pain with defecation may be indicative of involvement of the anal sphincters, whereas tenesmus may suggest a large or possibly fixed tumor. It is important to assess preoperative bowel function, including the presence of fecal incontinence as well as baseline sexual and urinary function. For distal rectal cancers, digital rectal examination can define tumor size, location from the anal verge, relationship to the anorectal ring, orientation within the anal canal (anterior, posterior, left, or right), and relative fixation (fixed, tethered, or mobile). Confirmation of these characteristics and biopsy for histologic confirmation of the diagnosis of rectal adenocarcinoma may be achieved by either flexible sigmoidoscopy or rigid proctoscopy. The latter method is preferred by some surgeons as the most accurate method to assess precise distance and location of the lesion from the anal verge or dentate line. Complete colonoscopy is essential to exclude synchronous lesions or other colonic diseases.

Primary tumor staging has become increasingly important to determine whether neoadjuvant chemoradiotherapy is indicated. Although CT scanning is the mainstay for initial assessment of distant disease and is useful to assess gross pelvic abnormalities such as direct extension to adjacent organs, it is not adequate for primary rectal tumor staging. ERUS may be useful to stage early lesions and can be used to assess tumor depth within the rectal wall (T1 and T2) and enlarged mesorectal lymph nodes (N-stage). However, MR of the pelvis should be considered using a protocol specific for staging rectal cancer. Pelvic MR has several advantages as compared to ERUS: (a) it is less operator dependent; (b) it provides a larger field of view beyond a few centimeters of the tumor including the pelvic sidewall and other adjacent structures; (c) it is more accurate in assessing lymph node involvement; and (d) it provides anatomically relevant information to the surgeon. Not surprisingly, pelvic MR has become the preferred method for local staging of rectal cancer.

In the United States, most advanced mid and low rectal cancers with evidence of lymph node involvement and/or transmural spread of the primary tumor are treated with neoadjuvant chemoradiotherapy followed 8-12 weeks later by radical surgical resection. Tattooing the distal edge of the tumor is useful to guide the subsequent resection and selection of a distal margin should a complete clinical response to neoadjuvant therapy occur. The rationale for neoadjuvant therapy is to decrease the risk of local recurrence and thus improve survival. Postoperative adjuvant chemotherapy is generally used as well to decrease the risk of distant metastases. In many parts of the world, the North American approach is criticized for potentially overtreating many patients. Many other protocols in the world call for use of less morbid, short-course neoadjuvant radiotherapy followed by radical surgery or for radical surgery alone if preoperative MR suggests that TME can clear the rectal cancer adequately.

Role of the Multidisciplinary Team

Although the colorectal surgeon has the primary responsibility to assess and direct the treatment of a patient with rectal cancer, appropriate decision making to optimize outcomes is greatly enhanced by a multidisciplinary team focused on rectal cancer care. Preoperative consultation with other specialty colleagues to plan treatment, achieve optimal oncologic outcome with the least morbidity, and to implement a coordinated and safe operation is essential. For the majority of advanced stage rectal cancers, medical and radiation oncologists will oversee a course of neoadjuvant chemoradiation. If there is involvement of the genitourinary tract or sacrum, preoperative consultation with a urologist,
neurosurgeon, or an orthopedic surgeon is advised. Patients with distal or mid rectal cancer should be seen preoperatively by an enterostomal therapist for counseling and marking of the abdominal wall for any potential stomas. In cases where it is not clear whether the procedure will be an APR versus AR and low anastomosis with a diverting ileostomy, both sides of the abdomen should be marked. Perineal wound closure may require plastic surgical consultation to plan a rotational myocutaneous flap. The new American College of Surgeons Commission on Cancer National Accreditation Program for Rectal Cancer Standards requires that every patient with rectal cancer is presented twice at the multidisciplinary tumor conference.

SURGERY

Special Surgical Considerations

Pelvic Floor Anatomy

APR requires that the surgeon be intimately familiar with the anatomy of the pelvis and, in particular, the pelvic floor and perineum (Figs. 34-1 and 34-2). The perineum is the area between the thighs extending from the pubis to the coccyx. Its upper boundary is the lower surface of the levator ani muscles. It is typically divided into an anterior urogenital region and a posterior anal region. The pelvic floor is a funnel-shaped, bilateral muscular plate that includes the three muscles of the levator ani (puborectalis, pubococcygeus, and iliococcygeus muscles) as well as the coccygeus muscle. The levator ani muscles are attached anteriorly to the pubis just lateral to the symphysis and posteriorly to the ischial spine. The puborectalis is a muscular loop without attachments to the coccyx with anterior fibers merging into the external sphincter. The pubococcygeus and iliococcygeus muscles arise from the arcus tendineus that extends from the pubis to the ischial spine. They insert on the ventral and lateral surfaces of the coccyx as well as into the anococcygeal raphe. The coccygeus muscle arises from the ischial spine and inserts into the lateral surface of the caudal part of the sacrum and the coccyx (Fig. 34-2). The pelvic floor muscles are covered by a parietal endopelvic fascial layer on their pelvic surface. The presacral Waldeyer’s fascia is a thickened part of the parietal fascia that covers presacral vessels and nerves and is attached to S3 and S4 sacral segments. Anteriorly, Denonvilliers’ fascia separates the rectum from the seminal vesicles and prostate (Fig. 34-3).

FIGURE 34-1 Caudal view of the pelvic floor muscles.

FIGURE 34-2 Lateral view of the pelvic floor muscles.

FIGURE 34-3 Lateral view of the parietal fascia in the pelvis (presacral, retrorectal, rectovesical).

Oncologic Insight—The “Waist”

Curative-intent APR is associated with higher rates of perforation, positive margins, and local recurrence than the rates observed after AR. These poor outcomes seem independent of tumor stage or size. Some authors have suggested that distal rectal cancers have a different biology and routes of spread compared to proximal lesions. For instance, 25% of transmural cancers in the distal half of
the rectum have lateral pelvic lymph node metastases located well beyond the dissection plane followed by TME. Although this problem may explain some of the poor outcomes observed after APR, there is increasing concern that the poor results may be due in large part to anatomic and technical considerations not previously considered. Specifically, it has been suggested that the poor outcomes after APR are due to the close proximity of the cancer to the circumferential resection margin at the level of the anorectum distal to the levator muscle sling. As opposed to a more proximal rectal cancer that is surrounded by the mesorectum enveloped within the endopelvic fascial plane, cancer in the distal anorectum has no comparable tissue surrounding it (Fig. 34-4). Nagtegaal et al. assessed cancers <5 cm from the anal verge and found that there was little or no levator and sphincter muscles surrounding the specimen at the level of the cancer. This area has now been termed the “waist” in an APR specimen. Salerno et al. found that the location of the “waist” was between 35 and 42 mm proximal to the anal verge, a site that correlates with the puborectalis muscle.

FIGURE 34-4 Conventional abdominoperineal resection (APR) dissection planes resulting in “waist.”

It is possible that a well-intentioned surgeon focused on performing a low anastomosis after TME for a distal rectal cancer may follow the mesorectum distally to the point where it thins and blends with the intersphincteric plane leaving almost no surrounding tissues on the cancer-bearing anorectum where it is excised, that is, at the “waist.” This maneuver is thought to result in high local recurrence rates. We agree with others that it is reasonable to modify the technique for radical APR to eliminate the “waist” and improve oncologic outcomes. The modifications described in detail include (a) stopping the abdominal dissection at the proximal level of the levator muscles and then (b) performing a more radical perineal excision of the levators including the puborectalis. Thus, instead of following the levators distally and inward to the anorectal ring, the surgeon can purposefully dissect through the levators laterally along the sidewall and include the soft tissue around the proximal aspect of the anorectal ring as part of the intact APR specimen. When properly done, the specimen will appear as a “cylinder” rather than a “waist.” Holm terms this modified technique of APR for distal rectal cancers as a “total ischioanal excision” (Fig. 34-5). Like Holm, the authors also believe that this modified technique is greatly facilitated by undertaking the perineal dissection with the patient in the prone jackknife position. The editors do not subscribe to this preference.

Peter McDonald and John Northover recently recovered old films from the archives of St. Mark’s Hospital in London, England, showing Percy Lockhart-Mummery performing a perineal excision, William Gabriel doing a perineoabdominal excision, and Oswald Lloyd-Davies undertaking a synchronous combined abdominoperineal excision of the rectum. In the films, after an extensive perineal incision and coccygectomy, the pelvis was cleared with lateral division of the levator muscles posterolaterally and the anterior dissection was carried up to the pouch of Douglas (Fig. 34-6). One wonders why modern surgeons abandoned this more radical perineal phase in favor of the more conservative “conventional APR dissection” that predisposes to “the waist” of an APR specimen. We speculate that the recent emphasis to do more distal low and ultralow anastomoses predisposed surgeons to alter what may be a key component of the deep pelvic dissection during an APR. Normally, when the dissection of
a rectal cancer that is clearly amenable to resection and anastomosis reaches the level of the levators, the surgeon selects a site for division of the rectum such that there will be an adequate distal margin, thus leaving the levators intact. We suggest that modern surgeons inappropriately apply the same basic technique used for low AR to the pelvic dissection for APR. Thus, when the dissection reaches the level of the levators, they follow the pelvic floor inward close to the anorectal wall before again widening the dissection plane at the level of the ischiorectal fossas. This technique unintentionally creates the “waist” in the specimen. When this method is utilized for more distal rectal cancers at or near the level of the puborectalis, surgeons may increase the likelihood of local recurrence by not adequately clearing the soft tissues from the pelvis at the level of the cancer. Indeed, a less radical APR can be done using the intersphincteric plane (Fig. 34-7A). Such technique may be appropriate for APR for proximal and mid rectal cancers in patients with poor sphincter function or some other contraindication for a sphincter-preserving proctectomy and may be the preferred APR technique
for benign diseases such as inflammatory bowel disease. However, for distal rectal cancers requiring APR, the surgeon is advised to consciously avoid the tendency to “cone in” on the dissection plane at the level of the levators. Conversely, the extralevator plane (Fig. 34-7B) may be appropriate and necessary for locally invasive distal rectal tumors to achieve a R0 resection.

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