腹腔镜全直肠系膜切除术（TME）癌症（图文演示）

12. Dissection/lower rectum
• Introduction
Dissection of the lower rectum is difficult in obese patients or in patients with a narrow and deep pelvis. It is in contact with vascular and nerve structures that must be preserved (Enker et al., 2000; Heald et al., 1998). To preserve genitourinary functions, care must be taken to avoid the middle hemorrhoidal vessels (which are occasionally large) and the parasympathetic nerve branches originating from posterior sacral foramina.
Dissection is performed posteriorly, laterally, then anteriorly to the rectum, alternating the right and left side as the rectum is progressively freed.
Laparoscopic freeing of the lower rectum is facilitated by the use of ultrasonic scissors or a vessel-sealing device.

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The posterior dissection is continued caudally on the posterior side of the rectum, anterior to the sacrum, once the sacrorectal ligament (Waldeyer’s fascia) has been opened. Care must be taken to avoid the anterior sacral venous plexus running on the anterior surface of the periosteum of the sacrum. This plexus is formed from posterior branches that lead to large 2-5 mm foramina from the third to the fifth sacral vertebrae before draining into the venous plexus of the intrasacral canal.
Further down the rectum is supported by the rectococcygeal ligament. Sharp division of this structure, using ultrasonic scissors or after coagulation, helps gain 1 to 2 cm over the posterior surface of the rectum, and also assists identification of the anal sphincter.

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Dissection is facilitated by the posterior retraction of the rectum, and anterior retraction of the vagina or prostate with the use of an instrument introduced in the suprapubic trocar (trocar E), which grasps Denonvilliers’ fascia.
At this level, dissection of the anterior surface of the lower rectum can only be achieved after lateral rectal dissection (especially in men).
1. Prostate
2. Rectum

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Low division of lateral ligaments exposes the lower pelvic space. This is done on the right side of the rectum, then on the left side. On the left side, the peritoneal reflection of the paracolic gutter should be incised down to the left lateral side of the rectum. One or more branches of the middle hemorrhoidal vessels joining the rectum on its anterior lateral surfaces are usually found on the lower part of lateral ligaments. These branches are infrequent, not always bilateral, and occasionally multiple. They should be controlled by clips or coagulation (bipolar forceps, vessel sealing device or ultrasonic scissors). At this level, the terminal branches of the pelvic nerve plexi run to the bladder, prostate, and genital organs (Enker et al., 1995; Enker et al., 2000).

11. Mobilization/upper rectum

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The rectum and its mesentery should be resected ''en bloc'' without infraction of the surrounding fascia to avoid any risk of local dissemination (Hida et al., 1997). The quality of the resection helps reduce the risk of recurrence (Kockerling et al., 1998).
1. Prostate
2. Seminal vesicles
3. Denonvilliers' fascia
4. Parietal fascia
5. Mesorectum
6. Fascia propria
7. Inferior hypogastric plexus

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Dissection of the rectum begins on its posterior surface anterior to the presacral fascia. The key to success is the opening of the presacral space between the fascia propria of the rectum and the presacral fascia (Enker et al., 2000). Anterior and lateral dissection follows. There is a major risk of injuries to nerve plexuses at the level of the upper inlet and laterally. These plexuses are medially protected by pelvic fascias. They can be very mobile and drawn medially during traction (especially on the right side), which accounts for the risk of injuries.
1. Presacral fascia
2. Parietal fascia
3. Hypogastric nerve

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The dissection of the presacral space begins anterior to the sacral promontory. Then it is followed caudally anterior to the presacral fascia. To achieve exposure, the rectum is retracted anteriorly and to the left, while maintaining the sigmoid colon in an upward position toward the left lower quadrant. Carbon dioxide helps open the space between the presacral fascia and the fascia propria of the rectum. Mobilization is completed laterally, just medial to the pelvic fascias that cover the right and left branches of pelvic splanchnic nerves.
The dissection is then fairly easily continued caudally down to the level of the fourth sacral vertebra. At this site, the 2 fascias almost fuse. The sacrorectal ligament (Waldeyer’s fascia) originates from here.
1. Presacral fascia

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The lateral rectal dissection should be done between the visceral perirectal fascia and the parietal lateral fascia of the pelvis (Enker et al., 2000; Heald et al., 1998). On the right side, the peritoneal incision at the base of the sigmoid mesocolon is lengthened caudally to begin the dissection on the right side of the rectum. The peritoneal incision is extended anteriorly to the rectovesical pouch while a grasper introduced in trocar D holds the rectum and retracts it to the left and anteriorly. This exposes the interfascial space. More caudally, the dissection approaches the superior margin of the lateral ligament, whose existence is subject to debate. The lateral side of the rectum is in closer contact with the lateral fascia at this point. The rectal branches of the pelvic splanchnic plexus that cross this space are divided.
1. Denonvilliers’ fascia

• Anterior rectal space

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Dissection of the prerectal space can be performed anterior to Denonvilliers' fascia (as described by Heald) or posterior to Denonvilliers' fascia.
In the classical technique described by Heald, Denonvilliers' fascia is transversely opened after the incision of the rectovesical pouch (Heald et al., 1998). Dissection is continued anterior to the fascia. In men, the seminal vesicles and the prostate are exposed. In women, the posterior surface of the vagina is exposed. In male patients, the prostatic and erectile nerves are found in this plane. Dissection is cautiously carried out anterior to Denonvilliers' fascia down to the inferior border of the prostate where dissection is continued posterior to the fascia.
1. Denonvilliers' fascia

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Dissection posterior to Denonvilliers' fascia is performed between the fascia propria of the rectum and Denonvilliers' fascia in contact with the posterior surface of the fascia. This technique of dissection is not recommended in tumors of the anterior rectal wall. The fascia propria of the rectum directly covers the seromuscular plane, and is not covered by fat, unlike the posterior and lateral surfaces of the rectum.
To find a suitable dissection plane, the rectum is gently retracted anteriorly with a grasper placed on the lower sigmoid colon and introduced through trocar D. Meanwhile the seminal vesicles of the prostate are retracted anteriorly with an instrument introduced through the suprapubic trocar E.
The plane between the fascias is identified once the rectovesical pouch has been opened. The posterior surface of the seminal vesicles is identified laterally, then dissected posterior to the parietal fascia. Dissection is then followed centrally toward the posterior surface of the prostate.
1. Denonvilliers' fascia

10. Mobilization/sigmoid

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Mobilization using the medial approach is well adapted for laparoscopy as it preserves the working space and requires minimal handling of the sigmoid colon and rectum.
Mobilization of the sigmoid colon follows the division of vessels. The approach is either medial to free the posterior attachments of the colon or lateral to free the lateral, then posterior attachments. We prefer using the medial approach, except in thin patients, whose sigmoid colon is very mobile, and in whom the lateral approach is more adapted. Using the medial approach, the lateral dissection of the sigmoid colon is done later, when the posterior and right lateral mobilization of the rectum is well advanced. It facilitates the left lateral dissection of the rectum.

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A medial approach is used. The posterior freeing of the sigmoid mesocolon is pursued laterally up to Toldt's line. In a medial to lateral order, the left sympathetic nerve trunk, the ureter, and genital vessels, covered with Toldt's fascia, are visualized during the dissection.
Once the inferior mesenteric vessels have been divided, the sigmoid mesocolon is retracted anteriorly (trocar E) to open the posterior space. The plane between Toldt’s fascia and the sigmoid mesocolon can then be identified. This plane is avascular and easily detached. It is exposed when dissection is continued posterior to the sigmoid mesocolon (not on the left lateral border of the aorta).

Laterally
Once the IMA has been divided, its distal portion is retracted anteriorly and to the left to better expose its left surface where the left sympathetic trunk runs, pulled by the traction. The sigmoid nervous rami heading to the left border of the artery are divided. The sympathetic trunk is left behind. Division of the sympathetic trunk at this level can cause retrograde ejaculation in men.
The dissection is continued to the left and anteriorly toward the posterior surface of the sigmoid mesocolon and descending mesocolon, to identify the IMV, which is then divided at the same level as the IMA or more cephalad, below the inferior border of the pancreas.

Caudally
Caudally, dissection is continued medially on the posterior surface of the IMA, then of the SRA posteriorly to its sheath. Nerve branches originating from the hypogastric plexus and running to the sigmoid mesocolon are then divided. The dissection is done anterior to Toldt's fascia and posterior to the sigmoid mesocolon and is followed laterally up to Toldt’s line. The lateral attachments are left undivided at this point to keep the sigmoid colon out of the operative field.
The lateral attachments are usually preserved but they can be divided using a lateral approach if a sigmoid loop impedes access to the pelvis.

1. Toldt's fascia
2. Ureter
3. Left plexic sympathetic trunk

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The sigmoid colon is freed laterally after the posterior dissection of the upper rectum.
The sigmoid loop is pulled toward the right upper quadrant (grasper in trocar F) to exert traction on the line of Toldt.
Once the line of Toldt has been opened, the posterior side of the left and sigmoid colon, which have been previously dissected by a medial approach, is accessed. Care must be taken to avoid gonadal vessels and the left ureter as they may be tethered by the medial traction exerted on the mesentery. In case of difficulty, a medial posterior approach should be associated with the lateral dissection. Identification of the ureter with a ureteral catheter (luminous stent or not) can be useful.
1. Ureter
2. Gonadal vessels
3. Base of sigmoid mesocolon

9. Risk/nerve damage

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There is a risk of injury to the hypogastric nerves (purely sympathetic) during ligation of the inferior mesenteric artery (IMA) at its origin and during dissection along the left border of the IMA.

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There is a risk of injury to the hypogastric nerves (purely sympathetic) during posterior dissection of the rectum in the presacral space.

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The inferior hypogastric nerves (mixed sympathetic and parasympathetic) may be exposed to injury if there is excessive lateral traction on the rectum during its lateral dissection.

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The cavernous nerves (parasympathetic), located at the postero-lateral border of the apex and base of the prostate, may be injured during the anterior dissection, particularly when it is performed anterior to Denonvilliers’ fascia.

8. Vascular approach

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In rectal cancer, the vascular approach is combined with a lymphadenectomy. Perirectal lymph nodes and lymph nodes of the inferior mesenteric chain are removed. However, division of the inferior mesenteric artery (IMA) at its origin and of the inferior mesenteric vein (IMV) at the inferior border of the pancreas is not mandatory to achieve an oncological resection.
The primary vascular approach allows for a medial and posterior dissection of the sigmoid mesocolon, while avoiding manipulation of the colon, rectum, and tumor (Okuda et al., 1998). This helps preserve the working space during the mobilization of the sigmoid colon and rectosigmoid junction.
The IMA should be clipped and divided before the IMV to avoid venous congestion in the mesocolon, which can result in oozing during dissection.
Before these vessels are divided, the sympathetic nerve trunks and the left ureter should be identified and preserved.
1. Sigmoid trunk
2. Superior rectal artery (SRA)
3. Aorta
4. Left colic artery (LCA)
5. Inferior mesenteric artery (IMA)

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The sigmoid mesocolon is retracted anteriorly using a grasper introduced in trocar E. The peritoneum is then opened cephalad, proceeding along the right anterior border of the aorta from the promontory up to the duodenojejunal junction. The incision then crosses to the left toward the splenic flexure to expose the anterior surface of the IMV.
CO2-induced dissection secondary to pneumoperitoneal pressure opens an areolar plane, which makes this step easier.
1. Promontory
2. Right border of the aorta
3. Third portion of duodenum

• Division of the IMA

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Division of the IMA near its origin, 1 cm from the aorta, and including the division of the LCA, aims at removing the surrounding lymph node tissue, to achieve an oncological resection. Dividing the IMA at its origin is associated with a risk of injury to the left sympathetic trunk situated on the left border of the IMA. This injury can be avoided if the dissection is carried out close to the IMA. Clips or the use of a vessel-sealing device are more precise and should be preferred to the use of linear staplers to avoid the division of the left sympathetic trunk and ureter.

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Once the peritoneum is opened, the dissection proceeds caudad to cephalad over the whole length of the incision, dividing the fatty and fibrotic tissues.
The aorta and the IMA are progressively identified. Once the right wall of the IMA has been identified, the artery is isolated near its origin below the duodenojejunal junction. The nerve branches that originate from the right para-aortic sympathetic trunk and the intermesenteric plexus and cover the IMA are divided one after the other. During dissection, the IMA is skeletonized while the branches of the periaortic sympathetic plexus are preserved.
The right branches of the superior hypogastric nerve that obliquely cross the aorta anteriorly and inferiorly to the IMA are preserved to avoid functional genitourinary sequelae. This step is crucial as it helps safe dissection of the IMA at its origin.

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Division of the IMA after the origin of the LCA combined with a large perivascular dissection also allows an oncological lymphadenectomy.
This technique helps to preserve the vascular supply of the left colon, but it can be an obstacle to splenic flexure mobilization. The sympathetic nerve trunks situated to the left of the IMA should be preserved. Their division can result in urinary dysfunction and ejaculation disorders in men.
1. Left colic artery (LCA)

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The IMV is identified to the left of the IMA, or in case of difficulty, to the left of the duodenojejunal flexure. It is then crossed anteriorly by the LCA, which then runs along its left border.
The IMV is retracted anteriorly with a grasper introduced in trocar E. Before division it is freed from the left sympathetic nerve trunk on its posterior surface. On its left border, it is freed from the LCA.
The IMV is divided between 2 clips below the inferior border of the pancreas, with care taken not to confuse it with the splenomesenteric trunk. The IMV can be divided later to preserve the ''tenting'' effect, which retracts the small bowel during the dissection of the sigmoid mesocolon.
1. Left colic artery
2. Inferior mesenteric vein

7. Exposure
• Patient preparation

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Exposure depends largely on the space available for retraction of the small bowel loops in the abdominal cavity, and on the positioning of the patient. Complete emptiness of the digestive tract greatly facilitates the layering of bowel loops. Emptying is achieved by a strict, low-residue diet commenced 3 to 8 days prior to surgery. We no longer use polyethylene glycol that was administered 2 days before surgery to complete bowel preparation. The day before, or even on the day of the operation, the patient is placed on a fibre-free diet and undergoes enemas.
Gastric emptying is done by means of a gastric tube.

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In addition to the pneumoperitoneal pressure (12 mm Hg), complete relaxation of the muscular wall is essential to create the working space.
1. Muscle relaxation
2. Distension of muscular wall
3. CO2 <= 12 mm Hg

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The greater omentum and the distal transverse colon are placed in the left subphrenic region and maintained in this position by the Trendelenburg position. An atraumatic retractor, introduced through trocar D, can also be used.

The jejunum is retracted toward the right upper quadrant, below the right transverse mesocolon. The right tilt and Trendelenburg position, along with an atraumatic retractor if needed, maintain the small intestine in this position.

The distal ileum is placed in the right lower quadrant along with the cecum. If the small intestine is too dilated, this operative maneuver may be difficult, notably in obese patients.

1. Retraction of the greater omentum
2. Trendelenburg position
3. Right tilt
4. Retraction of the intestinal loops to the right

&#8226; Specific cases

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The use of specific retractors, eg flexible retractors, is very useful during anterior dissection of the lower rectum. They are introduced in the suprapubic trocar E.
1. Retractor

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Obesity reduces the operating space. Obesity characterized by a flaccid muscular wall (female patients) is not a major handicap as ample working space remains and the mesocolon is longer. When obesity is characterized by a tonic muscular wall (male patients) and short, fatty mesenteries, the surgeon has to progressively layer the intestinal loops to expose the operative field.

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Adhesions, when present, are divided to free the bowel and achieve a better exposure. However, it is sometimes useful to preserve adhesions, notably at the level of the cecum, the sigmoid colon or the splenic flexure.

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The uterus can be an obstacle to good exposure of the pelvis. In post-menopausal patients, the uterus can be attached to the anterior abdominal wall by a transparietal suture. This suture is introduced halfway between the umbilicus and the pubis to make the axis of the vagina horizontal, thereby opening the rectovaginal space.

6. Exploration

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The first step is the exploration of the abdominal cavity, starting with a panoramic exploration to assess the tumoral extension. Visceral organs can be manipulated with atraumatic instruments to complete the exploration.
The length of the sigmoid loop, the quality of the wall of the sigmoid colon and its fixation in the pelvis, and the motility of the descending colon should be assessed.

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Recommended by some authors (Milsom et al., 2000), ultrasonography is carried out with a flexible, sterile, and reusable 10 mm probe.

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Localization of the tumor is indispensable for upper rectal tumors to avoid too large a resection of the middle and lower rectum. If the tumor cannot be visualized, localization is performed via endoscopy by dye-marking (india ink) at the beginning of the procedure or the evening before the procedure (Kim et al., 1997; Okuda et al., 1998).

5. Instruments

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We prefer to use 0° or 30° angle scopes with a 70° visual field.
Some surgeons use a 45° angle scope; others, like Milsom and Okuda, use a flexible fiberoptic laparoscope that offers multiple scope angulation during dissection.
1. 0° laparoscope
2. 30° laparoscope
3. Flexible laparoscope

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1. Grasper
2. Bipolar forceps
3. Ultrasonic scissors
4. Articulated linear stapler
5. Scissors
6. Circular stapler
7. Vessel sealing device

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1. Suction-irrigation device for lavage and dissection (lysis of adhesions)
2. Traumatic French needle to close trocar openings in obese patients
3. Purse-string applier
4. Clip applier
5. Wound protector
6. Extraction bag
7. Pelvic flexible retractor

4. Trocar placement

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Although a sigmoidectomy is possible with only 3 trocars, in complicated cases and especially when the surgeon’s experience is limited, more trocars are recommended. This improves safety, exposure of the operative field, and mobilization of the splenic flexure.
We prefer to use 6 trocars, with a trend toward reducing the size of trocars. The patient’s body habitus, previous surgical history, and the initial laparoscopic exploration via the supraumbilical trocar help in guiding the introduction of the various operating trocars.
Firm fixation of trocars to the abdominal wall can limit the risk of tumor seeding (Balli et al., 2000). Increased trocar stability also facilitates the procedure, and is achieved by adapting the size of the incision to the trocar, either by fixing the trocar to the skin with a suture or by using orthostatic trocars.

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Trocar A: 12 mm optical trocar
This first trocar is positioned on the median line above the umbilicus or 20 cm above the pubis in short patients.
This trocar accommodates a 0° optical.

&#8226; Operating

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Trocar B is a 5 mm trocar situated on the right midclavicular line, at the level of the umbilicus. It is used as an operating trocar during the dissection of the rectum and sigmoid colon and during the mobilization of the splenic flexure (caudal retraction of the left colon).
This trocar accommodates an atraumatic grasper.

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Trocar C is a 5 mm trocar situated on the right midclavicular line, 8 to 10 cm inferior to trocar B. It is used as an operating trocar during the dissection of the rectosigmoid. It is used as a retracting trocar during the mobilization of the splenic flexure (caudal retraction of the left colon).
At the end of the procedure, it can be replaced by a 12 mm or 15 mm trocar for the introduction of a linear stapler.
This trocar accommodates:
- scissors (monopolar, ultrasonic dissector, clip, staplers), bipolar hook, surgical loop, suction-irrigation device;
- an atraumatic grasper.

&#8226; Retractors

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Trocar D is a 5 mm trocar situated on the left midclavicular line, at the level of the umbilicus. It is used as a retracting trocar except during the mobilization of the splenic flexure, when it becomes an operating trocar.
This trocar accommodates:
- an atraumatic grasper;
- scissors (monopolar, ultrasonic dissector, vessel sealing device, clip, staplers), bipolar hook, surgical loop, suction-irrigation device.

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Trocar E is a 5 mm trocar situated 8 to 10 cm above the pubic bone on the median line. It is used as a retractor except during the division of the lower rectum when it can be replaced by a 12 mm or 15 mm trocar to introduce a linear stapler. A grasper is passed through it. It is used to expose the sigmoid mesocolon and the left mesocolon. A flexible retractor is passed through trocar E during the anterior dissection of the rectum.
This trocar accommodates a grasper, a suction-irrigation device, a stapler, and a flexible retractor.

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Trocar F is a 5 mm retracting trocar situated on the right midclavicular line below the costal margin. An atraumatic grasper is passed through it. It is used to retract the terminal portion of the small intestine laterally and to better expose the attachments of the omentum to the transverse colon during mobilization of the splenic flexure.
This trocar accommodates an atraumatic grasper.

3. Operating room set-up

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The patient must be positioned carefully, to avoid complications (nerve and vein compression, injuries of the brachial plexus) and facilitate the procedure and anesthetic monitoring.
The patient can be either secured by supports fixed above the shoulders, or strapped at chest level to prevent slippage.
- Trendelenburg position with a 15° to 25° tilt and a 5° to 10° right tilt;
- moderate lateral decubitus via a sandbag tucked below the left half of the body: this helps lower the organs to the right of the abdominal cavity;
- Lloyd-Davis position, allowing for both abdominal and perineal access: it is essential that the perineum be positioned at the distal edge of the table to facilitate the introduction of a circular stapler during colorectal anastomosis or to perform a colo-anal anastomosis;
- thighs and legs stretched apart with a slight flexure of hips and knees so that positioning of an assistant is easier and instruments can be better handled;
- right arm alongside the body so that an assistant can stand lateral to the right shoulder of the patient;
- left arm at a right angle or preferably alongside the body;
- gastric tube and urinary catheter to drain the bladder and stomach and control diuresis intraoperatively;
- heating device to limit the dissipation of heat.

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Although the procedure can be completed with 1 assistant, it is preferable to have 2 assistants and a scrub nurse, especially at the start of the surgeon’s experience with the technique.
The surgical team remains in the same position throughout the entire procedure.
1. Surgeon
2. First assistant
3. Second assistant
4. Scrub nurse
5. Anesthesiologist

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The operating table must allow for both abdominal and perineal access. A table that can be easily tilted by remote control, thereby facilitating perineal exposure, is recommended. The laparoscopic unit is located to the left of the patient. It includes a main monitor, a 3CCD camera (indispensable to perform the procedure in excellent conditions) and a high output (>= 9L/min) insufflator used to monitor pressures electronically. Its inertia should be low to make up for losses in carbon dioxide (induced or not).
The voice-controlled robotic arm or camera-holder is increasingly used to replace the assistant who holds the camera. It offers greater image stability during dissection.
1. Laparoscopic unit
2. Electrosurgical generator
3. Operating table
4. Monitors
5. Ultrasonic generator
6. Instrument table