Image and schematic diagram of Denonvilliers’ fascia in MRI (white arrow)
10.1.3.1 Clinical Significance
As mentioned above, Denonvilliers’ fascia is the front boundary of the mesorectum; therefore, sometimes, it is recommended to resect it completely in TME operation . Some researches indicated that there are an amount of metastatic lymph nodes with small diameters in anterior mesorectum; it was necessary to ensure the complete resection of the mesorectum. Some researches indicated that pelvic nerve was adjacent to the sides of Denonvilliers’ fascia; if the sides of Denonvilliers’ fascia were to be separated, injury should be avoided [11, 12] (Fig. 10.2). Our experience is that, under the condition that the front seminal vesicle or posterior vaginal wall is not injured, fibrous tissues of Denonvilliers’ fascia should be resected as much as possible; occasionally, capillary hemorrhage may occur from posterior vaginal wall, which could be controlled rapidly by surface coagulation with electric knife under argon mode.
Correlation between sides of Denonvilliers’ fascia and the pelvic plexus (male)/branches of pelvic plexus are in the trapezoidal area
The significance of Waldeyer’s fascia is that if the tough layer of the fascia is not disconnected, it is difficult to reach the bottom of the pelvis, and the coccyx cannot be revealed. As shown in Fig. 10.3, after entering the surgical plane between the fascia pelvis parietalis and fascia pelvis visceralis, this fascia must be sharply disconnected and separated to the upper level of coccyx. Thus, for both low-position anastomosis and APR operation, the most sufficient dissociation of the rectum can be achieved .
In the operation, after disconnection of Waldeyer’s fascia (white arrow), posterior rectal wall can be dissociated completely, and anococcygeal ligament can be revealed
10.1.4 Concept of Lateral Ligament of the Rectum
It is disputed whether or not there is an anatomic structure named lateral ligament of the rectum. According to histological research, the so-called lateral ligament is actually located between the middle and lower segments of the rectum and the lateral pelvic wall, which may include histological bundle consisting of nerve fibers, fat, and arteriae rectalis caudalis; however, the structure may vary. In the operation, during separation of lateral sides of the rectum, fibrous bundle structure was also found. Anatomical researches on lateral ligament lead to various results: Sato et al. believed that there was a lateral ligament, consisting of arteria rectalis media and branches of pelvic plexus nerve . Nano et al. also agreed that there was a lateral ligament structure; however, it consisted of only fibrous tissues, and the rectal arteries and branches of pelvic plexus nerve are located under the ligament structure  (Figs. 10.4 and 10.5).
Correlation of the lateral ligament, arteriae rectalis caudalis (MRA), hypogastric nerve, ureter (U), and pelvic plexus (the lateral ligament in the right diagram has been cut)
Ligation level of blood vessels in radical resection of rectal cancer. (a) Classical high ligation at the root of the inferior mesenteric artery. (b) Low ligation involving sigmoid arteries. (c) Low ligation only involving superior rectal artery
10.1.4.1 Clinical Significance
Although there is controversy on the existence of lateral ligament, the lateral bundle structure must be treated in the operation of rectectomy. In order to avoid injuring of the lateral pelvic plexus, sharp disconnection should be carried out by electric knife, and disconnection should be achieved near the rectum under the condition that the structure is maintained. There may be arteriae rectalis caudalis in the lateral ligament, but ultrasonic knife or electric coagulation can usually seal them, and clamping or ligation is not necessary; this is very important to maintain the completeness of the lateral side of the mesorectum.
10.1.5 Blood Supply to the Rectum
Blood vessels feeding the rectum are mainly from inferior mesenteric artery that comes from aorta abdominalis and then branches into the left colic artery, arteriae sigmoideae, and superior rectal artery. Arteriae rectalis caudalis from the internal iliac artery or internal pudendal artery also supplies blood to the rectum. Another important content of anatomy of rectum-related blood vessels is presacral venous plexus.
10.1.5.1 Clinical Significance
In traditional opinion of therapy against colon cancer, high ligation should be carried out to the inferior mesenteric artery. Classical high ligation means that the main trunk of the inferior mesenteric artery should be ligated and disconnected 2 cm away from aorta abdominalis at the root of the inferior mesenteric artery. However, in recent years, more and more findings of evidence-based medicine indicated that high ligation does not improve the prognosis of patients; instead, it may lead to complications such as ischemic necrosis . Therefore, NCCN guide recommends that, if intraoperative exploration finds there is no swollen lymph node at the root of the mesentery, routine high cleaning and ligation are not necessary; instead, ligation of the root of the superior rectal artery is enough; a part of branches of blood vessels in the sigmoid colon may be ligated selectively according to the intraoperative colon tension.
Arteriae rectalis caudalis, coming from the internal pudendal artery or internal iliac artery, is a small artery distributed at the lateral side of middle and lower segments of the rectum, of which the diameter is about 1–2 mm with a big anatomic variation. It is reported that the possibility of occurrence of arteriae rectalis caudalis is 22–100 % [14, 16, 17]. If it is found in operation, this blood vessel can be disconnected and coagulated with electric knife, while clamping and ligation are not necessary.
Presacral venous plexus is a structure of blood vessels in front of the sacral periosteum, consisting of two big lateral sacral veins and one median sacral vein. Presacral venous hemorrhage is a severe and dangerous intraoperative event during separation of posterior of the rectum, especially Waldeyer’s fascia, of which the anatomic background is that the presacral venous plexus will retract to sacral foramen after breakage . Therefore, during presacral venous hemorrhage, clamping and ligation cannot stop hemorrhage; moreover, it may tear presacral vein and aggravate hemorrhage. At present, there are two hemostatic methods in clinic: (1) Resect a piece of rectus abdominis, of which the diameter is 2 cm, press it on the bleeding point, and carry out electric coagulation (recommended electric coagulation value >100); then the charring of muscle will coagulate the contacted venous plexus  (Fig. 10.6); (2) press a tailor-made thumb pin on the bleeding point, penetrate the venous plexus, and stabilize it in the sacrum; with the help of local pressing, the purpose of hemostasis is achieved; it should be noted that the distance between the midline of the sacrum and the point where the thumb pin is pressing in should be less than 2 cm at S1 level, while at S5 level, it should be less than 1 cm, in order to avoid damaging the lateral sacral nervous plexus .
Presacral venous plexus and treatment of presacral hemorrhage (rectus abdominis electric coagulation method)
10.1.6 Pelvic Autonomic Nerve Preservation (PANP)
As the nerve controlling the rectum is usually resected along with the rectum in operation, what we stressed here is the pelvic autonomic nerve to be protected and preserved in the rectal operation. The critical nerve adjacent to the rectum usually has the following anatomical structure:
Hypogastric plexus: a nerve plexus resulted from confluence of the sympathetic nerve coming from thoracic vertebra 11 and lumbar vertebrae 2 and the lumbar splanchnic nerves coming from lumbar ganglia 3–4, formed in front of aorta abdominalis, at the branch of common iliac artery, also named as presacral nerve or nervi praesacralis.
Hypogastric nerve: two branches of nerve fascicles, of which the diameter is about 3 mm, starting from hypogastric plexus, going down with iliac vessels, bringing the adrenergic nerve into the pelvic organ, and controlling the function of ejaculation in male; hypogastric nerve is easy to identify in clinic, because it consists of thick yellowish fibers.
Pelvic splanchnic nerves: parasympathetic nerve fibers started from sacral nerve 2–4 and entered the right bottom corner of the pelvic plexus, which controls the function of erection in male.
Pelvic plexus: also named as hypogastric plexus. Pelvic plexus results from the confluence of hypogastric nerve, sacral splanchnic nerves, and pelvic splanchnic nerves and is located at the outer side of arteriae rectalis caudalis and lateral ligament of the rectum. Usually, the pelvic plexus is difficult to identify in a living body (Figs. 10.7 and 10.8).
(a) Hypogastric plexus. (b) Hypogastric nerve. (c) Pelvic plexus
The pelvic plexus (necrotomy) and trunk of hypogastric nerve (observed during operation)
10.1.6.1 Clinical Significance
In rectal surgery, especially radical resection of rectal cancer, the pelvic nerve structure should be protected as much as possible, in order to ensure that the patient can get good urinary and sexual function. In TME surgery, attention should be paid to the following: (1) After opening the lateral peritoneum at the inner side of the ureter, before entering the “holy plane,” attention must be paid to the dissociation and protection of hypogastric nerve at both sides. If dissociation is carried out directly along the loose gap that appears first, the hypogastric nerve would usually be disconnected at the posterior-lateral side of the rectum. Therefore, after the appearance of the gap, one should find the starting site of two hypogastric nerves from superior hypogastric nerve in front of sacropromontory (note the nerve trunk at this part is usually thick), sharply dissociate the main trunk of hypogastric nerve from the back of the mesorectum until the place where it enters the lateral pelvic wall to form the pelvic plexus, and then carry out the successive operation of TME. (2) Disconnection of the lateral ligament should be carried out adjacent to the rectum, in order to avoid injuring the pelvic plexus. (3) During the traction and dissociation of the sigmoid mesocolon to the branch of aorta abdominalis, the starting part of the hypogastric nerve at the left side is usually tracked together; at this time, the hypogastric nerve at the left side should not be injured .
10.1.7 Conception of Lateral Lymph Node Dissection (LLND)
Lateral lymph node metastasis usually occurs in advanced lower rectal cancer. Lateral lymph nodes mainly include the common iliac and internal iliac lymph nodes distributed along the direction of iliac vessels and the obturator lymph nodes distributed along the obturator vessels/nerve. The lateral dissection of rectal cancer should start from the branch of aorta abdominalis, and clean the fat/lymph tissues adhered to the front of the aorta and inferior vena cava; open the lateral peritoneum, clean the fat tissues on the surface of common iliac blood vessels and at the corner of common iliac blood vessels and iliopsoas muscle, and reveal the obturator nerve and blood vessels; further bare the obturator nerve and clean the obturator lymph nodes.
10.1.7.1 Clinical Significance
In recent years, according to the finding of evidence-based medicine, lateral lymph node metastasis indicated a worse prognosis, while lateral lymph node dissection increased the postoperative injury to urinary and sexual function significantly and could not improve the survival rate of patients . Especially, as application of neoadjuvant preoperative radiotherapy can lower the local incidence after operation, some researches indicate that lateral dissection after preoperative radiotherapy has no significant meaning . Therefore, lateral disconnection can act as optional operation at present; during the operation, if lateral swollen lymph nodes are contacted, they should be disconnected.
10.1.8 Concept of Anal Tube
The explanation of anal tube is different in anatomists, embryologists, pathologists, and surgeons. Usually, the following two classes of definitions are given for anal tube: the concept of anatomical, histological, embryological, and pathological anal tube is identical, while that closely related to surgeon is called as surgical or clinical anal tube. Usually, the length of surgical anal tube is about 4 cm, of which the range is from the upper edge of sphincter ani internus to the edge of the anus, while the length of anatomical anal tube is about 2 cm, of which the range is from the upper edge of dentate line (the upper edge of anal transitional zone) to the edge of the anus. The two concepts are not conflicted, and the former includes the latter. The horizontal tissues above and below the dentate line have completely different epithelial structure and nerve control, which have been described in detail in many textbooks. Perianal means the range 5 cm around the anus.
10.1.8.1 Clinical Significance
In order to judge the possibility of anus-preserving operation, surgeons usually carry out digital examination of the rectum to explore the position of tumor; the distance between the lower margin of tumor and the surgical anal tube is a factor to decide whether or not the anus can be preserved. If this distance is less than 1 cm, a distal margin with pathological negative is hard to obtain during operation; thus, the risk of local recurrence after anus preservation is increased significantly. The distance between the tumor and the dentate line (or the anatomical anal tube) has a less important meaning in guiding surgery operation.
10.1.9 Construction of Levator Ani Muscle
Levator ani muscle consists mainly of puborectal muscle, pubococcygeus muscle, and iliococcygeal muscle (Fig. 10.9). The iliococcygeal muscle, whose distal ends are located at the lateral pelvic wall and coccyx, respectively, is the main muscle to be treated during dissociation of posterior levator ani muscle.
Construction of levator ani muscle (outside and inside): from left to right, external rectal sphincter, puborectal muscle, pubococcygeus muscle, iliococcygeal muscle, and coccygeal muscle; the levator ani muscle is usually the generic term of the former three muscles
10.2 Abdominoperineal Resection (APR)
10.2.1 Development of APR
In 1908, Miles brought forward the conception of APR according to the achievements of study on lymph drainage of rectal cancer, which lowered the postoperative local recurrence rate of middle or lower rectal cancer significantly. In recent 70 years, APR operation was always the standard operation for lower rectal cancer . With the development of concept and skill of TME, more and more colorectal surgeons care about the whole dissociation of the mesorectum, other than stress on the resection range of levator ani muscle and fat tissues in ischiorectal fossa. With the development of pathology of rectal cancer and image technology, more and more attention have been paid to the question how to ensure to get a negative circumferential resection margin (CRM) after radical resection of rectal cancer . The study of evidence-based medicine also indicated that APR operation has a worse prognosis than the anus-preserving LAR operation, because of the higher rate of positive CRM after APR operation, which may lead to local recurrence . Therefore, on the basis of TME, the cylindrical APR operation, in which the resection range of levator ani muscle is extended, has attracted attention of colorectal surgeons gradually .
10.2.2 Indications of APR Operation
Because of the development of lower stapling technique, a distance <6 cm from the lower margin of tumor to the edge of the anus is no longer the absolute indication of APR operation. We suggest that the common indication is the rectal cancer, of which the distance between tumor and the anus is less than 5 cm. Application of APR needs correct preoperative staging, good operation, and cautious intraoperative decision.
The following conditions were often met: (1) Preoperative MRI judged that the tumor had invaded levator ani muscle, or digital examination of the anus indicated that the distance between tumor and upper edge of surgical anal tube was less than 1 cm. (2) During operation, pelvic canal stenosis or giant tumor was founded; thus, the lower rectum was difficult to be dissociated and stapled. (3) After sufficient dissociation of the rectum, satisfactory distal incisal margin (>1 cm) was not yet obtained, or rapid pathological examination indicated a positive recisal margin. (4) After local resection of early lower rectal cancer, pathological examination indicated a positive incisal margin or a lesion over T2 stage.
10.2.3 Preoperative Preparation for APR Operation
10.2.3.1 Routine Preoperative Preparation
Preoperative evaluation of physical state and nutrition support; preparation of blood and blood transfusion (when necessary); cleaning the vagina for female patients; skin preparation of the perineum and abdomen.
10.2.3.2 Preoperative Intestinal Tract Preparation: Insertion of Gastrointestinal Decompression Tube and Urine Drainage Tube
In classical surgery, a routine 3-day intestinal tract preparation should be carried out before operation for rectal cancer, including oral intake of antibiotics, mechanical lavage of intestinal tract, preoperative gastrointestinal decompression, and urine drainage tube insertion. However, researches of evidence-based medicine in recent years indicated that preoperative oral intake of antibiotics and mechanical lavage of intestinal tract could not decrease the incidence of postoperative complications such as anastomotic leakage and infection [28, 29]. After routine intestinal tract lavage, the patients may suffer a higher incidence of postoperative anastomotic leakage and infection . In addition, according to the rapid recovery opinion advocated at present, preoperative intestinal tract preparation, gastrointestinal decompression, and urine drainage tube insertion may be carried out to some patients with rectal cancer but not routinely .
10.2.3.3 Permanent Colostomy and Marking
Please refer to Sect. “10.5.10.1 Colostomy.”
10.3 Steps of APR Operation
10.3.1 Selection of Anesthesia, Position, and Incision
As APR operation has a large resection range and will take a long time, general anesthesia should be used. Lithotomy position should be adopted to reveal perineum. It should be noted that (1) after anesthesia, the operation table can be adjusted so that the head is in a lower position and the feet are in a higher position; thus, the small intestine will be set at the front of surgery field; (2) the coccyx of patients should be extruded, and the angle between thighs and trunk should be less than 90°, so that the perineal region can be revealed enough to facilitate operation; (3) during the setting of lithotomy position, the position of patient’s leg should be adjusted to avoid pressing the common peroneal nerve. The incision is usually selected at the center of the abdomen around the navel, of which the bottom should reach the pubic symphysis and the top boundary depends on the condition of the patient. During the incision of abdominal wall to the lower part, avoid injure bladder. For female patients, womb can be suspended to facilitate revealing.
10.3.2 Exploration of Abdominal Cavity and Pelvic Cavity
After entry of the abdomen, explore whether or not there is ascites, hepatic metastasis, or peritoneal metastasis and collect information of abdominal visceral organ such as the colon and stomach; explore whether or not there are swollen lymph nodes at the root of the inferior mesenteric artery, in front of aorta abdominalis, or at the area of iliac vessels; for female, attention should be paid to the bilateral ovary. Finally, explore the tumor and pay attention to the dissociation degree of the tumor and the relation of the tumor to adjacent organs and pelvic wall; during operation, preoperative pelvic MRI image should be combined to identify the local condition of tumor.
10.3.3 Preligation of Rectal Vessels and Intestinal Canal
After complete exploration, the operation table can be adjusted so that the head is in a lower position and the feet are in a higher position; push the small intestine to the side of the head. Ligate the intestinal canal with tape at the boundary of the rectum and sigmoid colon above the tumor. Tract the tape so that the sigmoid mesocolon has a certain stress, touch to identify the direction of superior rectal artery and sigmoid arteries, open the peritoneum at the surface of the mesentery, and preligate at the root of superior rectal artery. For patient who has a shorter length of sigmoid colon, a narrow pelvic cavity, or an overweight body, under the precondition that the proximal end of the rectum is long enough to be brought out of abdominal wall, the rectum-sigmoid colon can be disconnected with an occluder; thus, traction and dissociation of proximal end of the rectum are helpful for revealing the posterior rectal wall.