The oncologic removal of the rectum often requires both an abdominal and a perineal approach. During the abdominal portion of the procedure, the superior rectal vessels are controlled, the rectum and mesorectum dissected, and colostomy created. During the perineal portion, the rectum and anus are detached from the ischiorectal fat, the levator muscles, and whatever portion (if any) of the distal portion of the genitourinary organs not planned for removal. The boundary between the abdominal and perineal parts of the procedure is delineated by the levator muscles. The abdominoperineal excision (APE) of the rectum is now much safer than when it was first introduced more than a century ago. However, despite the advances in surgical technique and perioperative care, it remains a surgical challenge due to the complex anatomy of the pelvis.

For many years after its original description, the APE was the only surgical option for patients with rectal cancer. As a result of advances in the understanding of the dissemination of rectal cancer, along with improvements in surgical ­technique and instrumentation, and the use of neoadjuvant therapy, most rectal cancers are now treated with sphincter-­saving procedures (SSPs). APE has been relegated to the treatment of very distal rectal cancers involving the sphincter complex or the levator muscles. Therefore, the division of the levators muscles is a critical step of the operation that determines the oncologic outcomes.

Almost immediately following the initial description of APE, surgeons began introducing minor modifications to the procedure. The number of options has recently expanded with the introduction of minimally invasive techniques. The abdominal part of the operation can be performed as an open, laparoscopic, or robotic procedure; the perineal part can be performed with the patient in lithotomy or in the prone position. In any case, successful APE requires perfect knowledge of the anatomy of the abdomen, pelvis, and ischiorectal fossa, as well as adherence to a few sound surgical principles. The APE operation is very similar to the pelvic exenteration with perineal phase, which is described in Chapter 8. The current chapter will specifically focus on the APE for distal rectal cancers.

Surgical treatment of rectal tumors did not become feasibleuntil the introduction of the colostomy by the French ­surgeon, Jean Amussat, during the Napoleonic wars. Distal proctectomy through the perineum, which reaches within a few centimeters of the promontory, was already being ­performed by Lisfranc and others in the 1830s. However, it was not until the late nineteenth century that surgeons really began to regularly perform this operation.¹

The perineal excision of the rectum was performed in 2 stages. The first stage consisted of a minilaparotomy to inspect the peritoneal cavity for signs of tumor dissemination, and to create a loop or double-barrel colostomy. In the second stage, performed several days later, the surgeon removed the anus, the ischiorectal fat, the levators, the rectum, and at least a portion of the mesorectum up to the level of the promontory.² This operation had 2 flaws: (1) it did not remove the lymph nodes located along the superior rectal vessels, and (2) it left a portion of colon and mesocolon attached to the distal limb of the stoma, which often resulted in a chronic perineal sinus. Earnest Miles is credited with introducing the modern APE in his seminal article published in 1908.³ In the years prior to this seminal publication, Miles, like most of his contemporaries, had treated rectal cancer with ­conventional perineal proctectomy. Of the 57 patients with rectal cancer whom he treated, 54 developed recurrent tumor within 3 years following surgery. Detailed autopsy studies on these patients revealed that most of the recurrences were located in the portion of mesorectum that had been left in place during surgery and along the superior rectal vessels, arising at the pelvic peritoneum, the pelvic mesocolon, or the lymph nodes located at the bifurcation of the left common iliac artery. Miles called these areas “the zone of upward spread.” The perineal proctectomy addressed the lateral and distal tumor spread, but not the “upward spread.” The operation he devised to address this was performed in one stage, and included the creation of an abdominal colostomy, removal of the entire “pelvic colon because its blood supply was contained in the zone of upward spread,” the “whole of the pelvic mesocolon below the point where it crosses the common iliac artery,” the “group of lymph nodes situated over the bifurcation of the common iliac artery,” and the anus, ischiorectal fat, and levator muscles “as far outward as their origin from the white line as to include the lateral zone of spread.” Although this operation was initially associated with a rate of perioperative mortality higher than 40%, it soon became the standard treatment of rectal cancer. Attempts to broaden the scope of the operation by removing the lymph nodes along the internal iliac vessels failed to provide a survival advantage, and increased the risk of perioperative complications and long-term bladder dysfunction.

Miles started the abdominal part of the operation with the patient supine in the Trendelenburg position. He then turned the patient to the right lateral and semiprone position to complete the perineal part. In later years, other surgeons introduced modifications to make it simpler and safer. The synchronous combined abdominal and perineal excision, ­performed simultaneously by two different teams, was first performed by Kirschner and popularized by Lloyd–Davis, who introduced the leg rests that allowed the patient to be placed in the lithotomy position. The Lloyd–Davis modification has been preferred for more than 100 years.⁴

Recent advances in understanding the mechanisms of recurrence after rectal cancer surgery have re-emphasized 2 aspects of Miles’ operation probably ignored by many surgeons for decades: the need to remove the entire mesorectum, and the lateral division of the levator muscle. Although some surgeons had always performed the dissection of the “pelvic mesocolon” (now called mesorectum) in the bloodless areolar space “anterior to the sacral ligaments,” as proposed by Miles, many were performing the dissection inside of the mesorectum to avoid the vascular and neural pelvic structures. Incomplete excisions of the mesorectum can leave behind portions of the lymph node–bearing fat surrounding the rectum, and even expose the tumor itself. The need to remove the entire mesorectum in every rectal cancer patient using sharp dissection following the areolar plane outside the fascia propria of the rectum was reintroduced by Heald in 1982.⁵ The importance of the presence of tumor at the circumferential resection margin was reported in 1985 by Quirke,⁶ who demonstrated a much higher rate of recurrence when tumor reached the circumferential resection margin than when the margin was free of tumor.

The second important development is the renewed emphasis on dividing the levators “as far outwards as their origin from the white line, so as to include the lateral zone of spread.” Although in his original description Miles emphasized the importance of dividing the levators laterally,³ close to their insertion in the pelvic sidewall, many surgeons divide the levators closer to the rectal wall. These changes occurred over time as surgeons extended the abdominal dissection progressively closer to the levator muscles to perform anastomosis in patients with tumors amenable to a sphincter-saving procedure. However, extending the abdominal dissection to the pelvic floor, in a patient with distal rectal cancer that infiltrates the levator or the anal sphincter, leads to the division of the levators close to the rectal wall, increasing the risk of positive circumferential resection margin and local recurrence.⁷

These deviations in surgical technique from the original procedure described by Miles are considered, by some, to be the main reason why APE for low rectal cancer is associated with a greater risk of recurrence compared to low anterior resection (LAR) for higher tumors. The newly named “cylindrical,” or “extralevator” APE, is an attempt to avoid these shortcomings by emphasizing complete excision of the mesorectum and lateral section of the levator muscles (Figure 7-1).

Adenocarcinoma located in the distal rectum is the most common indication for an APE. Most patients with tumors penetrating the muscularis propria or metastasized to the mesorectal lymph nodes require removal of the rectum and the mesorectal envelope. For most patients with midrectal tumors, the rectum is transected below the end of the mesorectum and intestinal continuity is re-established by double-stapling colorectal anastomosis. For patients with distal rectal tumors, the surgeon must decide whether removal of the tumor with a negative margin is compatible with sphincter preservation, or whether it requires APE. The need to achieve a safe margin of normal rectal wall distal to the tumor, in order to avoid local recurrence, must be balanced against the ability to retain enough rectum attached to the anus so that safe colorectal or coloanal anastomosis (CAA) can be achieved. For decades, 5 cm was the minimum length of normal rectal wall distal to the tumor that was considered oncologically safe. Later studies have shown that cancer cells rarely spread distally along the bowel wall farther than 1 cm from the macroscopic distal end of the tumor. Consequently, the required margin of normal bowel distal to the tumor was reduced to 2 cm.⁸ Recent evidence suggests that margins as short as 1 cm do not increase the risk of recurrence, particularly in patients treated with neoadjuvant chemoradiation therapy.⁹ Therefore, in most patients, the need for APE, rather than SSP, is due to the inability to obtain a negative circumferential resection margin, rather than a negative distal margin. In general, APE is indicated when distal rectal cancer penetrates beyond the muscularis propria and infiltrates the levator muscle or anal sphincter. A digital examination and an endoscopy provide valuable information about the relationship of the tumor to the anal canal. High-resolution magnetic resonance imaging (MRI) and computed tomography (CT) modalities that provide axial, sagittal, and coronal views can demonstrate the relationship of tumor to the levator muscles and the external anal sphincter with a high degree of accuracy.

In the past, before optimal imaging of the rectum was widely available, many patients with rectal cancer were brought to the operating room with the intention of determining intraoperatively whether the sphincter was salvageable by LAR or CAA, or whether APE and permanent colostomy would be required. The decision to perform an APE was made only after the rectum had been mobilized to the pelvic floor and the tumor was found to be too close to, or to infiltrate, the levator muscle or the anal sphincter. In trying to decide intraoperatively if SSP was feasible, distal dissection was often carried to the levator hiatus, where the rectal wall is not covered by mesorectum and is in direct contact with the levator muscles. If the surgeon found that SSP was not feasible, then the levators were usually divided at the point of their dissection from the pelvis, very close to the rectal wall in the specific area where the tumor was usually located. These “waisted” APE specimens often resulted in exposure of the tumor at the radial resection margin.¹⁰ However, the new high-resolution imaging modalities help surgeons decide preoperatively whether a patient is a candidate for SSP or will require APE.¹¹ Knowing in advance what procedure is to be performed reduces uncertainty for the patient and improves operative planning and execution.

Abdominoperineal excision of the rectum is also the operation of choice for patients with anal squamous cell carcinoma that persists or recurs after chemotherapy and radiation, because these tumors usually involve the anal canal and levator muscle. Occasionally, APE is required for less common tumors of the anorectal region such as anal melanoma, sarcoma, or gastrointestinal stromal tumors. Extended APE is sometimes required for vulvar, vaginal, or prostate cancers involving the distal rectum or anal sphincter. In addition, APE of the rectum is part of the total proctocolectomy performed for patients with familial adenomatous polyposis or other hereditary polyposis syndromes. Finally, APE is commonly performed in patients with inflammatory bowel disease, either as part of a proctocolectomy for ulcerative or granulomatous colitis, or as a separate procedure in the setting of isolated anorectal Crohn disease.

The key to successful APE is a perfect understanding of the anatomy of the rectum and anus, the vessels and nerves of the pelvis, the pelvic floor musculature, and the ischiorectal fossa. The key structures described in this section are depicted in Chapter 2.

The pelvic floor, also known as the pelvic diaphragm, comprises the levator ani and coccygeus muscles. The levator muscle is a thin, broad layer of muscle that inserts in the inner wall of the pelvis and unites with the muscle of the opposite side to form the greater part of the pelvic diaphragm. The anterior portion inserts in the posterior aspect of the pubic bones lateral to the symphysis and runs posteriorly and obliquely to join the perineal body. These are known as the levator prostate or pubovaginalis. The next muscular fascicle, known as the puborectalis, extends from the posterior aspect of the pubic bone and loops around the back of the rectum, becoming continuous with the muscle of the opposite side. The lower fibers of the puborectalis intermingle with the fibers of the upper portion of the external sphincter. The ileococcygeus and pubococcygeus insert in the pubis and in the tendinous arch of the obturator fascia, extending obliquely downward and backward from/toward the perineal body, the anal sphincter, the anococcygeal ligament, and the coccyx. The levator muscles create a funnel-shaped diaphragm with a central opening delineated by the puborectalis sling and the symphysis of the pubis, which allows passage of the urethra and the rectum in both males and females, and the vagina in females. The puborectalis, pubococcygeus, and ileococcygeus are divided during APE. The coccygeus muscle extends from the spine of the ischium and the sacrospinous ligament and inserts in the coccyx. The coccygeus muscle is in the same plane as the levators but is more posterior, and it is usually not divided during APE.

The rectum corresponds to the distal 15 cm of the large bowel, but neither its beginning nor end is sharply defined by specific anatomical landmarks. Proximally, the sigmoid colon transitions into the rectum at the rectosigmoid junction. This is a poorly defined region where the relatively narrow lumen of the sigmoid colon widens to become the rectum. From the outside, the outer longitudinal muscles forming the taenia coli (characteristic of the sigmoid colon) spread diffusely, becoming the uniform longitudinal muscular layer of the rectum. This occurs approximately at the level of the promontory, but the relationship of the rectosigmoid junction to the promontory depends on the laxity of the mesorectum. Distally, the rectum transitions into the anal canal at the level of the anorectal ring, a palpable anatomical landmark that corresponds to the impromptu of puborectalis on the bowel wall. The anal canal extends from the anorectal ring to the anal verge, the palpable groove between the distal edge of the internal sphincter and the subcutaneous portion of the external sphincter. The rectum contains the 3 valves of Houston, which are occasionally used as reference to locate rectal lesions. However, it is more practical to describe the location of a rectal tumor by measuring the distance of the lesion from the anal verge. This is best accomplished with a rigid proctoscope that permits simultaneous viewing of the tumor, the anal verge, and the measuring marks on the instrument.

The mesorectum is the visceral mesentery of the rectum derived from the dorsal mesentery of the hindgut. It contains the terminal branches of the superior rectal vessels and the lymphatic drainage of the rectum. The upper portion of the rectum is located above the anterior peritoneal reflection; it is covered with peritoneum in the front and on both sides, and has a posterior mesorectum attached to the concavity of the sacrum, which is a continuation of the mesentery of the sigmoid colon. Below the peritoneal reflection, the rectum is completely extraperitoneal and fully surrounded by mesorectum. At that level, the mesorectum is a cushion of loose connective tissue posterolaterally surrounding the rectum, covered by a thin, glistening membrane called the fascia propria of the rectum. It posteriorly extends from the promontory to Waldeyer fascia, a condensation of connective tissue spanning the area from the fourth sacral vertebra to the anorectal ring. Posteriorly, the mesorectum is separated from the presacral fascia by an avascular plane of loose areolar tissue. The plane between the fascia propria of the rectum and the presacral fascia is the natural plane of dissection during radical proctectomy.

The mesorectum is thick posteriorly, where it has a characteristic bilobular appearance. Anteriorly, however, it is either absent (in the upper intraperitoneal portion of the rectum) or reduced to a thin layer of areolar tissue (in the mid and distal rectum). The fascia propria of the rectum is also thinner anteriorly than posteriorly. In the front, the thin mesorectum is separated from the urogenital organs by a remnant of the fusion of two layers of the embryological peritoneal cul-de-sac known as Denonvilliers fascia. The anatomic appearance of Denonvilliers fascia varies, from a barely visible translucent membrane to a distinct, tough, leathery layer of connective tissue separating the seminal vesicles or vagina from the rectal wall. The fascia propria of the rectum and Denonvilliers fascia are important anatomic landmarks in rectal cancer surgery.

The mesorectum distally tapers off as the rectum funnels down toward the anorectal ring, where the longitudinal layer of the muscularis propria of the rectum is in direct contact with the levator muscle. The proximity of the rectal wall to the levator muscle should be taken into consideration when deciding between APE or SSP in the setting of transmural rectal cancers located at or below the level of the anorectal ring.

Below the peritoneal reflection, the mesorectum intermingles on both sides of the pelvis with a condensation of connective tissue surrounding the autonomic nerves that pass from the pelvic plexus to the rectum. These bilateral condensations of the endopelvic fascia are known as lateral ligaments and connect the pelvic sidewall with the mesorectum. In some individuals, the lateral ligaments contain accessory middle rectal vessels; the middle rectal artery usually immediately runs above the levator muscles.

The blood supply of the rectum primarily comes from the superior rectal artery, which is the continuation of the inferior mesenteric artery after it gives off the left colic artery. The superior rectal artery gives several sigmoidal branches before diving into the mesorectum, where it gives multiple branches to the rectum. The superior rectal vein has a parallel course to its homonymous artery, on its way to join the left colic vein to form the inferior mesenteric vein draining into the splenic vein. The lower portion of the rectum also gets blood supply from the internal iliac vessels. The middle rectal artery, an inconsistent branch of the inferior vesical artery, is usually located deep in the pelvis, running over the levator muscle toward the distal wall of the rectum. The inferior rectal artery is a branch of the pudendal artery and provides blood supply to the anal canal and anal sphincter. The middle and inferior rectal vessels anastomose with the upper rectal vessels to supply enough blood to the entire rectum. As in other locations, the middle and inferior rectal veins follow the course of the ­homonymous arteries and drain into systemic circulation through the internal iliac veins. Anastomosis between the superior and middle rectal vessels represents the potential portosystemic communication that becomes relevant in patients with portal hypertension.

The anatomy of the autonomic pelvic nerve system is particularly relevant when performing APE, because it is close to the plane of dissection during different parts of the operation. Damage to these nerves can result in urinary dysfunction, sexual dysfunction, or both. The hypogastric plexus, located in front of the aorta, contains predominantly preganglionic sympathetic fibers originating from the lumbar sympathetic trunk. The fibers of the hypogastric plexus converge at the level of the aortic bifurcation into well-­defined hypogastric nerves, which laterally course across the internal ileal vessels toward the lateral pelvic sidewall. There they join the splanchnic pelvic nerves, containing primarily postganglionic parasympathetic fibers from S3 to S4, to form the pelvic plexus. Branches of the pelvic plexus provide innervation to the distal ureter, the vas deferens, the seminal vesicles, urinary bladder, and prostate. Some branches of the pelvic plexus also provide innervation to the distal rectum, passing though the lateral rectal ligaments, or lateral stalks. Finally, distal to the lateral rectal ligaments, the distal pelvic plexus forms the urogenital neurovascular bundles that pass close to the posterolateral aspect of the seminal vesicles or the vagina, extending toward the apex of the prostate and the neck of the bladder.

The pudendal nerve provides most of the innervation of the perineal region, and must be preserved during the perineal portion of APE. It originates from the inferior aspect of the sacral plexus and contains sensitive, motor, and parasympathetic postganglionic fibers. Passing behind the sciatic spine it enters Alcock canal in the lateral wall of the ischiorectal fossa, and branches into the inferior hemorrhoidal nerve, the perineal nerve, and the dorsal clitoral nerve. Some of these branches are divided during perineal dissection.