Medial to Lateral Dissection
The procedure begins with the patient in Trendelenburg position. A Pfannenstiel (or vertical suprapubic) incision is created, usually 6-9 cm in size, just large enough to insert one's gloved hand. The general rule is to make the incision as large as the surgeon's glove size (for example, size 7 glove = 7-cm incision). Superior and inferior flaps are created of the anterior rectus fascia, and the rectus abdominus is split in the midline and the peritoneum opened. Before inserting the hand-assist device, a hand is placed into the abdomen to confirm that the umbilical area is free of adhesions (for the optical cannula insertion), and a 10-mm supraumbilical port is inserted while the hand lifts the abdominal wall and shields the underlying bowel loops from injury. A supra-pubic incision is preferred to one below the umbilicus, because the size of the hand port device may cause collisions with the infraumbilical
port. The hand port is fashioned to the suprapubic incision, and carbon dioxide pneumoperitoneum is established. Additional ports are placed, as in Figure 9.2.2. The laparoscope is placed through the supraumbilical cannula and the abdomen explored.
The surgeon and assistants set up for the right colon mobilization, as illustrated in Figure 9.2.1. The patient is placed in steep Trendelenburg with the right side up. The surgeon inserts his/her left hand into the hand port, and with a bowel grasper in the right hand through the left abdominal port, the transverse colon is retracted cephalad and the omentum is lifted above the transverse colon. The proximal small bowel is swept to the left of the patient and the terminal ileum is swept inferiorly, exposing the duodenum and the anterior aspect of the right colonic mesentery. The ileocecal region of the bowel is placed on antero-lateral traction to identify the ileocolic artery and vein, which bowstring through the mesentery when placed on traction; this pedicle is usually easily identified. The proximal segment of the ileocolic artery and vein normally courses just inferior to the duodenum, and the duodenum is an important initial landmark. The first assistant helps by both holding the camera and by retracting the transverse colon cepha-lad using a bowel grasper placed through the epigastric port. The thumb and index finger of the surgeon's left hand are used to grasp the ileocolic artery and vein through the mesentery to retract it anteri-
orly. A monopolar scissors is used to incise the mesentery just inferior and superior to the ileocolic vessels, isolating them (Figure 9.2.3). These vessels are then divided at their appropriate level; in the case of benign disease, they are divided comfortably away from the origin. The vessels can be divided using a vessel-sealing device such as the LigaSureTM device, or the artery and vein can be isolated separately using an endo-scopic dissector and clipped (Figure 9.2.4). In nearly 87% of cases, the right colic artery arises as a tributary of the ileocolic artery and not from the superior mesenteric artery,2 and the ileocolic artery is usually divided proximal to the take-off of the right colic artery.
The left hand is then used to retract the distal edge of the divided ileocolic vessels, exposing the posterior aspect of the right colonic mesentery. The assistant helps by lifting up the thin mesenteric edge above the duodenum. A medial to lateral retromesenteric dissection is performed, first by bluntly sweeping down the second portion of the duodenum, separating it from the posterior aspect of the transverse mesocolon (Figure 9.2.5). The head of the pancreas is exposed carefully, as this dissection can result in a considerable amount of venous bleeding if performed too vigorously. This plane is maintained and dissected laterally, staying in the plane anterior to the retroperitoneal fascia as the fascia is bluntly swept down. The hand is inserted further and further underneath the mesentery, as Gerota's fascia is further swept away laterally, until this dissection is carried underneath the right
colon to the lateral abdominal wall, as well as underneath the hepatic flexure. Within the ileal mesentery, the ileal branch of the ileocolic vessel must not be torn by aggressive dissection underneath the cecum.
Next, the terminal ileum is grasped with the left hand and retracted cephalad, and electrosurgery is used to detach the ileum from the retroperitoneal structures. Occasionally, the hand can become an obstruction to the dissecting instrument, and in this case, the hand is removed and the monopolar shears inserted directly through the hand port and manipulated with the left hand. The dissection is taken around the appendix and cecum, sweeping away the residual retroperitoneal attachments to the cecum. With the left hand retracting the right colon medially, the monopolar scissors is inserted into the right abdominal port and used by the first assistant to divide the lateral attachments of the right colon (Figure 9.2.6). If the medial dissection was taken to the lateral abdominal wall, this attachment should be a thin sheet of peritoneum. This dissection is taken in a cephalad direction, eventually mobilizing the hepatic flexure. Depending on the case, the monopolar shears may need to be used from the epigastric port closer to the hepatic flexure. Placing the patient in reverse Trendelenburg position may help with hepatic flexure takedown.
At this point in time, again in Trendelenburg position with the right side up, the dissecting instrument is placed through the left abdominal port, and the omental dissection is begun. The assistant, still standing at the left of the patient, grasps the omentum, placing anterior traction
on it, as the transverse colon is held by the left hand of the surgeon. Initially starting this dissection in the midtransverse colon and working back toward the hepatic flexure seems to allow for the easiest dissection. Larger omental vessels are divided using the LigaSure™, and care is taken to stay close to the colonic wall. After the omentum is freed from the hepatic flexure, the omental dissection is performed from right to left, mobilizing the omentum off of the transverse colon as one would in conventional surgery (Figure 9.2.7). With the surgeon positioned on the left side of the patient, dissection should be limited to the middle colic vessels and the transverse mesocolon to the right of the midline. Dissection to the left side of these areas becomes very difficult and should be reserved for later phases of the operation.
The assistant, from the left side of the patient, retracts the transverse mesocolon anteriorly, displaying the middle colic vessels (which can be visualized behind the peritoneum with traction) to the surgeon. In nearly one-third of the cases, an arterial branch will be present to the right colic angle. A finger is passed underneath the cut mesenteric edge, and is hooked around this branch, isolating it. This vessel is divided using the LigaSureTM, or clipped and divided. The head of the pancreas is further swept down gently, and a finger is passed behind the middle colic vessels. It is important to remember that the vascular anatomy of the middle colic system is extremely variable, and there can be up to five different vessels behaving as arteries and branches. The pattern of the "true middle colic artery," or a single stem branching into a right and left branch may be present in only 46% of cases. Especially in more obese patients in whom the middle colic vessels may be "hidden" in a thickened mesentery, the hand-assisted approach allows the surgeon to feel pulsations within the mesentery. The right branch of the middle colic artery is identified and a finger is hooked around it, as a mesenteric window is created between the right and left branches (Figure 9.2.8). This vessel is divided. Then, a finger is passed around the left middle colic branch, and a window made to the left of this branch. This branch is then divided in the same way. When the dissection is completed to the left of the middle colic vessels, attention is turned to the left colon.
The operating room setup is changed as in Figure 9.2.1B. Still in steep Trendelenburg position, the patient is airplaned with the left side up. The small bowel loops are swept to the right of the patient. Near the ligament of Treitz, a left colic artery is usually seen branching from the inferior mesenteric artery (88% of cases). This vessel bowstrings and becomes visible through the mesentery when anterolateral traction is placed on the left colon. The surgeon's right hand is inserted through the hand port, and this vessel is grasped and retracted anteriorly. The assistant helps with retraction of the left colon with a bowel grasper inserted from the left abdominal port. With the monopolar shears inserted through the right abdominal port (manipulated with the left hand), mesenteric windows are created on both sides of this vessel, and the vessel is isolated and divided with the LigaSure™ device (Figure
9.2.9). Adjacent to the ligament of Treitz (superior to the inferior mesenteric artery) is probably the easiest place to enter the correct retro-mesenteric plane to start a medial to lateral mobilization, and in benign disease this approach is preferred. With the right hand lifting the cut edge of the mesentery and exposing the mesenteric window, the retroperitoneal fascia including Gerota's fascia is bluntly swept down from the posterior aspect of the mesentery (Figure 9.2.10). The assistant helps in exposing this window. The hand is inserted further into this window and dissection is continued to the lateral abdominal wall. Initially, this plane is dissected inferiorly as far as possible, behind the first sigmoidal branch. Then, the same plane is developed in a cephalad direction, continuing to sweep down the retroperitoneal fascia until near the top of the kidney. Here, the mesentery of the colon attaches to the inferior border of the pancreas, and attention must be given so that the dissection does not carelessly continue posterior to the pancreas and injure the splenic vein.
At this point in time, the right hand is removed from the hand port, and the monopolar scissors is inserted through the hand port itself for lateral mobilization of the sigmoid colon. It is helpful for the assistant to move to the right side of the patient to assist through the epigastric port. Medial traction is placed on the sigmoid colon using bowel graspers, and the lateral attachments of the sigmoid colon are taken down with the monopolar scissors (Figure 9.2.11). Sharp and blunt dissection is used to carefully "peel" the sigmoid colon and mesosigmoid away from the retroperitoneal structures. The left ureter and gonadal vein
should be identified underneath the preserved retroperitoneal fascia. The dissection using this approach is taken in a superior direction until difficult. The left hand is placed back into the hand-assist device, and the monopolar shears inserted into the left abdominal port. The sigmoid colon is grasped and placed on medial traction, and the lateral attachment of the descending colon is further divided, heading toward the splenic flexure (Figure 9.2.12). This attachment should be a thin sheet of peritoneum if the medial to lateral retromesenteric dissection was taken to the lateral abdominal wall. Near the splenic flexure, the dissection becomes easier with the surgeon standing between the legs and, therefore, this lateral dissection is paused. The mobilization of the left and sigmoid colon is completed and, with this surgical method, the inferior mesenteric artery and sigmoidal branches remain intact. The sigmoidal branches may be isolated and divided intracorporeally before moving on to the splenic flexure dissection, or they can be left for later division using open surgery through the Pfannenstiel incision.
For the splenic flexure takedown, the surgeon moves between the patient's legs, as in Figure 9.2.4. The left hand is placed through the hand port, and the LigaSure™ 5 or 10 mm through the left abdominal port. The first assistant moves to the right of the patient and inserts bowel graspers into the right abdominal and epigastric ports. The patient is placed in a reverse Trendelenburg position.
The splenic flexure has several attachments, including the spleno-colic ligament and the greater omentum. It is also held in place posteriorly by its retroperitoneal attachment, and the dissociation of Gerota's fascia from the posterior aspect of the mesentery in the previous
surgical step allows for the splenic flexure to "drop down" toward the surgeon, distancing itself from the spleen and allowing for a safe dissection. The left hand grasps the proximal descending colon and retracts this inferiorly and medially. The assistant retracts the omentum as this is dissected off the wall of the splenic flexure using the LigaSure™ (Figure 9.2.13). Then, the splenocolic ligament is carefully dissected from laterally, staying as close to the colon as possible. This left to right dissection is continued, entering the lesser sac, and the omentum is further mobilized from the distal transverse colon. Here, the remaining omental attachments may be dissected from right to left, back toward the splenic flexure to meet the previous dissection. This should liberate the entire splenic flexure, and the remaining colonic attachment becomes the mesentery to the splenic flexure and distal transverse colon. By retracting the transverse colon toward the pelvis, the dorsal aspect of this mesenteric attachment is exposed. This mesentery is dissected with the LigaSure™ from lateral to medial until the pancreas is visualized and, at this level, the dissection is continued inferior to the pancreas (Figure 9.2.14). An intermesenteric vessel may be present between the middle and left colic arteries, and mesenteric vessels within this mesentery are divided. By dynamically retracting the transverse colon inferiorly from several directions, the final peritoneal attachments of the transverse colon are visualized and divided. Now,
the entire abdominal portion of the colon should be free. The colon is placed above the small bowel loops, ready for extraction, as the patient is placed back in a Trendelenburg position.
Through the hand-assist device, the transverse colon is grasped, and the entire colon is exteriorized (Figure 9.2.15). The remaining portions of the operation will utilize conventional "open" surgical techniques. Staying inferior to the cut edge of the ileocolic vessels, the ileal mesentery is divided toward the ileocecal junction, dividing the ileal and accessory ileal branches. The terminal ileal wall is cleaned off and divided. If a stapled ileorectal anastomosis is planned, a purse-string is placed into the cut edge of the ileum and the center rod and anvil of a circular stapler are inserted into it. If an end ileostomy is planned, a linear cutting stapler is used to transect the distal terminal ileum. As the ileum can easily twist around its mesentery inside the abdomen, two seromuscular stay sutures are placed into the wall of the terminal ileum, and the sutures are left outside the body to prevent twisting as the ileum is placed back into the abdomen.
The specimen is now free proximally, and attention is given to the sigmoid colon. Any attachments of the sigmoid colon that were not adequately divided intracorporeally are dissected at this time through the Pfannenstiel incision using open techniques. The colon is retracted caudally, and the remaining sigmoidal arteries are isolated and divided (preserving the inferior mesenteric artery), until the top of the rectum is reached (Figure 9.2.16). The preservation of the inferior mesenteric
artery will assure good blood supply to the rectal stump (especially if the distal sigmoid colon is left intact), and the hypogastric nerves will remain completely untouched. The top of the rectum is stapled using a 30- or 45-mm linear stapler as in conventional surgery, liberating the total colectomy specimen. The end of the ileum is located, and a stapled ileorectal anastomosis created by inserting an end-to-end stapler into the rectum (CEEA 28 or 31 mm). Both donuts are checked for integrity, and a leak test is routinely performed by immersing the anastomosis in saline and injecting air under pressure into the rectum. The handassisted approach allows the surgeon to place reinforcing sutures if necessary, and for surgeons that prefer a single-stapled anastomosis (instead of a double-stapled one), a Proline purse-string can easily be placed into the mouth of the rectal stump. If an end ileostomy is planned, a stoma aperture is created in the right lower quadrant just as in open surgery, splitting the rectus abdominus muscles.
If there is concern about malignancy, the inferior mesenteric artery should be divided laparoscopically very proximally as part of a complete lymphadenectomy. In this case, the surgical approach dealing with the left and sigmoid colon will change. The setup for this portion of the operation will be as in Figure 9.2.2. With the patient in Trendelenburg position with the left side up, the surgeon stands on the right side of the patient, with the first assistant between the legs. The first assistant places a hand through the hand-assist device and retracts the sigmoid colon anterolaterally, out of the pelvis. Starting at the sacral promontory using monopolar scissors, the surgeon creates a wide incision in the mesosigmoid, staying just posterior to the inferior mesen-teric artery. An avascular plane is present here, and this is bluntly developed, sweeping the right and left hypogastric nerves away from the posterior aspect of the inferior mesenteric artery. The mesentery is opened in a superior direction toward the origin of the inferior mesen-teric artery, further developing this plane (Figure 9.2.17). Using the hand to retract the inferior mesenteric pedicle anteriorly, the retroperi-toneal fascia is swept down, developing the retromesenteric plane from medially to laterally. The left ureter and gonadal vein are visualized and protected. After identification of these structures, the inferior mes-enteric artery and vein are isolated proximally and divided (Figure 9.2.18). The surgeon then inserts the right hand into the hand port, lifting the cut edge of the mesentery, and blunt dissection is continued laterally to the abdominal wall, staying anterior to the retroperitoneal fascia as the fascia is swept down. The dissection is initially taken inferiorly underneath the sigmoid colon, and then cephalad, sweeping Gerota's fascia down from the posterior aspect of the left colonic mesentery, heading toward the top of the left kidney. At this point, the lateral attachments of the sigmoid and left colon are taken down as in the previous description.
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