The pelvis consists of two compartments: a parietal outer compartment and a visceral inner compartment. The parietal compartment is built around the skeletal part of the pelvis (sacrum, pubic, iliac, and ischial bone). Muscles on the inside of the pelvis are the piriformis muscle, coccygeal muscle, levator ani muscle, and obturator muscle. The common internal and external iliac artery and vein belong to the parietal compartment as well as the lumbosacral nerve plexus.

If the tumor is close to the inferior hypogastric plexus (by means of palpation or MRI scan), or if a total pelvic exenteration is performed, a plane lateral to the inferior hypogastric plexus can be chosen. Resection of the internal iliac artery and vein creates laterally another few millimeters of extra margin. Resection of muscles is demanding and technical difficult. Some surgeons even advocate resection of bony structures and sacrificing the lumbosacral plexus (partially) [10].

Sometimes enlarged obturator lymph nodes are seen on the pretreatment MRI. The obturator space is cleared if the nodes are still visible on the MRI after the chemoradiation. This resection is not en bloc with the primary tumor and usually vessels do not have to be sacrificed. The obturator nerve is spared during this dissection.

A complete removal of the levator muscle has become standard (extralevator resection) if an abdominoperineal resection with a wide local resection is necessary [11]. The prone position may facilitate this procedure especially if the os coccyx or even a part of the sacrum has to be removed. The patient is turned in the jackknife or knee-chest position. Special care has to be given to this positioning. A detailed description of the knee-chest position is as follows. Gravity will cause flexion of hip and the knees. To prevent sliding away, a roll is put under the upper legs. The operation table is tilted some degrees of anti-Trendelenburg to balance the patient in a way that most of the weight is transferred to the upper legs. The chest is supported with a large, firm but soft roll. In this way the abdomen is hanging freely, facilitating ventilation. Performing the perineal phase in the knee-chest position instead of the standard position in stirrups has several advantages: (a) exposure to the operative field is better; (b) hydrostatic venous pressure is lower, reducing bleeding; (c) assistance and tutoring is feasible; and (d) gravity will pull the perineum downward, flattening the pelvic floor. Contraindications for this position are instability of circulation, stiff hip joints, above-knee amputation, and severe overweight (>100 kg).

The perineal phase is started with closure of the anus with a purse string stitch. The perineal skin is incised in an ellipse extending to the perineum ventrally and extending some centimeters lateral to the anus. Dorsally the incision extends below the coccyx. In selected cases this incision is extended to include the coccyx or distal sacrum. Ventrally, the posterior vaginal wall in female patients may be included in the resection. The ischiorectal fat is then divided using diathermia. Some branches of the inferior rectal artery and vein are encountered. During the continuation of this dissection, the inferior outer surface of the levator ani muscle and its insertion to the obturator muscle will be exposed. Ventrally the perineal muscle will be divided. This will expose the bulbus of the penis in male patients or the posterior vaginal wall in female patients. In male patients the ventral plane leads from the bulbus to the urethra. A transurethral catheter is helpful to identify the urethra by palpation. After identifying the urethra, it may be difficult to continue in the correct plane on the prostate because of a sharp dorsal angle in the dissection plane. During dissection on the bulbus, urethra, and prostate, the left and right levator muscles stand out as vertical columns which can be divided. Step by step the prostate is dissected and the levator is divided on its origin. The levator should be cut above the horizontal plan of the dorsal site of the prostate in order to prevent damage of the autonomic nerves entering the prostate laterodorsally. On the posterior side the dissection plane created during the laparotomy will be met. In some cases some upward dissection has to be made to reach this plane. Some authors advocate entering the retro rectal plane below the tip of the coccyx. This technique of the perineal phase ensures that the levator ani muscle is resected en bloc with the specimen, avoiding a positive margin in distal T3/T4 tumors because of a thin distal mesorectal layer. It is called the extralevator resection. The removed specimen has less perforations and a wider margin in comparison with the conventional technique [12]. As the levator is completely resected, the perineal wound presents as a large defect in the pelvic floor. An omentoplasty is used to close this perineal defect. If it is not possible to make an omentoplasty, a rectus abdominis flap and in rare cases the gluteus flap will be used. After fixating the omentoplasty or rectus flap in the perineal defect, the subcutaneous fascia is approximated. In cases with preoperative fistula to the pelvic floor, a large skin defect has to be created. Under these circumstances a rectus abdominis flap with skin island is used [13]. Finally, the skin is closed with interrupted sutures.

The rectal cancer extends sometimes to the anterior compartment of the pelvis. Organs within this internal compartment are the rectum and bladder and the genitourinary organs: in females the uterus; the round ligament of the uterus, tube, and ovaries; and the vagina and in males the seminal vesicles, the ductus deferens, and the prostate.

Radical resection of the tumors invading one of these structures requires resection of the affected organs. This may result in partial bladder resection, selective resection of the seminal vesicles, and resection of the uterus or posterior vaginal wall en bloc with the total mesorectal excision. After resection of the vagina, a reconstruction should be offered to a patient whom is sexually active. Several techniques are available such as the rectus abdominis flap, split skin on a mold [14].

Resection of both the prostate and bladder is called a total pelvic exenteration. Pelvic exenteration is in the initial phase similar to a standard low anterior resection or abdominoperineal resection. The patient’s position in stirrups, the midline incision from the pubic bone to just above the umbilicus, the careful inspection of the abdomen and liver for metastatic disease, and the exposition of the pelvis by installing a self-retaining retractor keeping the small bowel and omentum away are all the same. After mobilizing and dividing the sigmoid, the superior rectal artery is divided close to the inferior mesenteric artery. The presacral plane is developed. It is helpful to identify the hypogastric nerves at this stage and find the plane posterior to these nerves, contrary to the regular rectal resection. This outward plane follows the outer layer of the visceral pelvic compartment. It is filled with loose areolar tissue; some small vessels cross the layer. Often, this plane is edematous by the neoadjuvant radiation therapy. The ureter is encountered at its crossing of the iliac artery. The ureter is divided at this point, putting a temporarily small (Chap. 8) silicone catheter in the ureter to allow observation of diuresis. Dividing the ureter at this point allows for an anastomosis to the Bricker loop at the promontory. A longer ureter could allow a Bricker anastomosis deeper in the pelvis, at risk for leakage in the pelvis as it is not covered with tissue and for obstruction in the case of recurrent disease. On the ventral side, the loose areolar tissue of Retzius’ space is divided. The remaining bridge to the pelvic sidewall is now divided. This dissection is carried out close to the internal iliac artery and vein and its subsequent branches and just outside the pelvic autonomic nerve plexus. A bipolar vessel sealing device may facilitate dissection in the narrow working space in this part of the operation. At the caudal edge of the pubic bone, firm attachments of the prostate to the bone are found: the puboprostatic ligament. Under and lateral to this ligament is an extensive venous plexus. It can be the cause extensive bleeding if the dissection is carried forward into this plexus. After bilateral incision of the endopelvic fascia, the branches of the vesicoprostatic plexus are ligated and the dissection is continued within the prostatic capsule toward the pelvic floor. The urethra is then encountered and divided. The final part of the resection has two options. In case of a distal tumor, a perineal resection is mandatory (see perineal resection). In case of a more proximal tumor, future herniation is prevented by leaving the pelvic floor intact.