Since Goh et al. applied laparoscopic techniques to radical gastric cancer surgery in 1997, laparoscopic radical gastric cancer treatment has become technically mature after more than 10 years of continuous accumulation. However, due to the complexity of anatomy and technical operation, laparoscopic radical treatment of gastric cancer is not as popular as laparoscopic colon surgery. The reasons for this are.
1) The anatomical level of radical gastric cancer surgery is complex, spanning multiple anatomical levels from the inferior and anterior pancreatic regions to the superior pancreatic region, unlike in colorectal surgery, where the entire surgical separation process is unified within a single fascial level, i.e., Toldt’s and the anterior sacral space, both in the abdominal part and in the pelvic part.
2) The lymph nodes in the gastric region are distributed along the perigastric vessels, pancreas, and bile duct parietal, and these structures need to be properly protected and not damaged. In radical treatment of colorectal tumors, the regional lymph nodes are removed by dissecting the blood vessels directly from the roots, for example, in radical rectal cancer, the peri-vascular lymph nodes are removed by dissecting the inferior mesenteric artery from the roots.
3) Reconstruction of the digestive tract after radical resection of gastric cancer requires more complex lumpectomy techniques.
In principle, laparoscopic techniques are only a technical tool and do not change the principles of surgical treatment. In order to better carry out laparoscopic radical gastric cancer treatment, it is necessary to conduct a more in-depth analysis of the basic principles of radical gastric cancer treatment, surgical anatomy, and make necessary adjustments according to the characteristics of laparoscopic techniques. Radical treatment of gastric cancer, like the radical treatment of other tumors of the digestive tract, requires whole-block resection of the tumor and regional lymph. The standard clearance range for radical treatment of gastric cancer is D2 clearance. Radical treatment of gastric cancer by open surgery has been proven that it is technically feasible to remove the entire stomach and the lymph nodes in the region under the premise of ensuring D2 clearance. Based on the experience of open surgery, the surgical anatomy and surgical pathway for radical treatment of gastric cancer (using total gastrectomy as an example) can be roughly summarized as follows.
1) Bottom-up. That is, starting from separating the gastrocolic ligament, separating upward along the fused fascial gap between the dorsal gastric mesentery and the transverse colonic mesentery, reaching the lower edge of the pancreas and then dealing with the subpyloric region (group 6 lymph nodes), and then crossing the surface of the pancreas to the suprapancreatic region to clear the group 5, 7, 8, 9, and 11 lymph nodes. The sequence of separation from the bottom to the top allows the stomach to be gradually freed and the relevant areas to be continuously exposed.
2) Three regions, three levels. In the bottom-up dissection process, the separation steps can be broadly divided into the inferior, anterior and superior pancreatic regions, with different levels of separation and different anatomical landmarks in the three regions, and the pancreas is at the center of the three regions.
In the subpancreatic region, after opening the gastrocolic ligament, the level of separation enters the fused fascial gap between the greater omentum and the transverse colonic mesentery, which is an avascular gap located in front of the mesocolic vein, and during the separation of the lower margin of the pancreas along the surface of this vessel towards the root of the transverse colonic mesentery, the superior mesenteric vein and Henle’s stem are revealed, and the level of separation enters the deep surface of the pancreatic (posterior) fascia. Embryologically, the anterior and posterior fascia of the pancreas originate from the posterior layer of the dorsal mesentery of the stomach and fuse with the anterior lobe of the transverse colonic mesentery below the pancreas. Separation along Henle’s trunk immediately adjacent to the pancreas to the right reveals the right gastroretinal vein and then the right gastroretinal artery, while the level of separation shifts from the deep pancreatic (posterior) fascia below the pancreas to the deep pancreatic envelope in front of the pancreas between the anterior pancreatic fascia and the intrinsic pancreatic fascia.
In the anterior pancreatic region, the gastroduodenal artery is the main marker of separation, and the posterior part of the duodenal bulb can be freed by separating upward along this vessel, and the pancreatic pericardium is also lifted along with the anterior lobe of the transverse colonic mesentery to the superior margin of the pancreas to reach the suprapancreatic region.
The suprapancreatic area is a difficult area for radical lymphatic dissection of gastric cancer. On the one hand, there are important vessels such as the celiac trunk, hepatic artery, splenic artery, posterior gastric vessels, and coronary vein, which make the separation easy to bleed; on the other hand, the separation in this area needs to cross the dorsal gastric mesentery and enter the deep Toldt’s hiatus, which is located in the superficial part of the anterior renal fascia, and the separation in this hiatus can reach the posterior part of the pancreatic gastric body and reveal the left and right diaphragm feet.
There is a process of crossing the anatomical level from the subpancreatic region to the anterior pancreatic region and then from the anterior pancreatic region to the superior pancreatic region, and the process of crossing the anatomical level is accompanied by the treatment of blood vessels and the clearance of lymph nodes. In other words, lymphatic clearance for radical treatment of gastric cancer requires dissection and separation within the non-fascial level. This is the reason why radical treatment of gastric cancer is more difficult than that of colorectal cancer. Between the inferior and anterior regions of the pancreas, the manipulation of the vessels is dissociated, thus there is no problem of vascular protection, but between the anterior and superior regions of the pancreas lymphatic clearance needs to be performed with the protection of the vessels, thus the perivascular gap constitutes an important level and pathway.
3) Vascular pathways. In all three regions mentioned above and in the corresponding three separated levels, blood vessels are important anatomical landmarks. In the inferior pancreatic region, the vascular landmark is the mesocolic vein, and in the anterior pancreatic region the vascular landmark is the gastroduodenal artery, both of which are significant in guiding the correct anatomical level. The vascular landmarks in the superior pancreatic region are the ventral trunk and its branches: the common hepatic artery – the intrinsic hepatic artery, and the splenic artery. These vessels are the objects to be protected and the boundaries of lymphatic dissection, so lymphatic dissection of the suprapancreatic area is a difficult and important point in the radical treatment of gastric cancer. The lymph nodes in the suprapancreatic area are distributed along the celiac trunk – hepatic artery – intrinsic hepatic artery – splenic artery, and the lymph nodes must be separated along these arteries to be cleared.
Another object involved in the vascular pathway is the portal vein. Within the hepatoduodenal ligament, the portal vein is located posterior to the innominate hepatic artery. At the superior margin of the pancreas, the bifurcation of the common hepatic artery, the gastroduodenal artery, crosses right over the beginning of the portal vein. In order to reduce the risk of bleeding from the portal vein, the portal vein can be revealed by dissection between the hepatic artery and the gastroduodenal artery below and the superior margin of the pancreas before perihepatic lymph node dissection, followed by separation of the anterior portal vein gap toward the hilar portion. The significance of the separation of the anterior portal vein gap is to determine the posterior limits of periportal lymphatic clearance of the hepatic (innominate) artery, which is beneficial to improve the safety of the procedure.
To summarize, there are three key anatomical steps in the management of the area above the pancreas: first, the hepatic artery-gastroduodenal artery-intrinsic hepatic artery is dissected along the superior margin of the pancreas to reveal the hepatic artery, while the celiac trunk-splenic artery is revealed later; second, the portal vein is revealed. The common hepatic artery and gastroduodenal artery form an arch at the superior margin of the pancreas, and there is a loose connective tissue gap between the underside of this arch and the superior margin of the pancreas, which can be carefully separated to reach the surface of the beginning of the portal vein, and the tissue gap in front of the portal vein can be completely opened by doing blunt dissection along the surface of the portal vein into the hepatoduodenal ligament. During this process it should be noted that there may be small portal vein branches which will be very passive once bleeding occurs. After the above two steps are completed, the lymphatic clearance within the superior margin of the pancreas, suprapylorus, and hepatoduodenal ligament will have a safe boundary, and the thoroughness and safety of lymphatic clearance will be ensured. The third critical dissection is the revealing of the diaphragmatic foot, and this step is relatively safe. The hepatogastric ligament is opened along the lower edge of the liver to reach the right edge of the cardia, and the anterior and posterior layers of the hepatogastric ligament begin to separate at the right edge of the cardia, with the anterior layer moving to the anterior plasma membrane of the cardia and the posterior layer moving to the posterior wall of the lesser omental sac. There is a clear boundary between the right side of the gastro-pancreatic fold and the foot of the diaphragm. Opening the plasma membrane here for blunt separation separates all the adipose lymphoid tissue of the posterior part of the subcardia from the foot of the diaphragm, whose anatomical level is continued with the Toltd “s gap in front of the left anterior renal fascia. Revealing the diaphragmatic foot can also be done from the left side, mainly for total gastrectomy with preservation of the spleen, i.e. by opening the gastro-diaphragmatic ligament when the splenogastric ligament is separated to the left side of the cardia, revealing the left diaphragmatic foot first and then separating it to the left.
The above points are an anatomical analysis of the surgical pathway based on the oncological principles of treatment of gastric cancer, which should be applicable not only to open surgery but also to laparoscopic surgery as well. However, due to the characteristics of laparoscopic surgery, some details need to be carefully analyzed in the implementation of the above path. First, the limitations and characteristics of the laparoscopic view require different exposure strategies during surgery and appropriate adjustments to the surgical steps. Second, laparoscopic surgery requires a high degree of bleeding control, and bleeding that may not be serious in open surgery may result in a laparoscopic mid-surgery.
In terms of surgical exposure, the view of the laparoscope radiates from the umbilicus in all directions, and the exposure of the entire surgical procedure should revolve around this view. The bottom-up step of open radical gastric cancer treatment is exactly adapted to this requirement, but it needs to be adjusted in the left-right direction. Looking at the surgical videos of domestic and foreign experts as well as our experience, the sequence of separation from the left side to the right side is more consistent with the principles of human efficacy when the operator stands on the left side of the patient and goes through the left upper abdominal puncture opening, as an example, for the right-handed surgeon. In this way, during the separation of the gastrocolic ligament, the dissection of the lower and upper margins of the pancreas, the view direction and the separation surface are vertical, and the view and the operating rod always present a good angle.
In the radical treatment of gastric cancer, the risk of bleeding mainly exists in two areas, one is the process of subpyloric gastrocolic trunk exposure and the treatment of the right vein of the gastric omentum, where the vein is relatively thin and easy to rupture, and there are more anatomical variants, so it is the first difficult hurdle in the radical treatment of lumpectomy gastric cancer. Secondly, the left side of the superior margin of the pancreas and hepatoduodenal ligament, where the bleeding mostly originates from the right gastric vein, coronary vein and posterior gastric vein, which are indefinitely located, deeper, and closely related to the portal vein, and improperly handled can easily lead to failure and intermediate surgery.
Personally, I have experienced that the anatomical strategy from the left to the right is beneficial for the prevention of bleeding, both in the subpyloric region and in the suprapancreatic region. In the subpyloric region, the mesocolic vein is used as a guide to separate first toward the superior mesenteric vein surface at the lower edge of the pancreas, a process that does not encounter obvious vessels. After reaching the inferior margin of the pancreas, do not rush the separation to the right, but free the gap behind the duodenal bulb immediately adjacent to the pancreas before carefully dissecting to the right to expose the gastrocolic trunk and the right gastroretinal vein. When freeing the right gastroretinal vein, we should be alert to the superior anterior pancreaticoduodenal vein that may converge from the posterior side, and the specific strategy is not to separate too close to the pancreas, but to wait until its posterior gap is free before approaching the root of the right gastroretinal vein.
At the superior margin of the pancreas, a left-to-right strategy is equally beneficial for hemorrhage prevention. This can be done by starting with exposure of the splenic artery, then moving upward into the anterior gap of the anterior renal fascia and exposure of the left phrenic foot, followed by progressive exposure and treatment of the left gastric artery. From the intraoperative observation of radical gastric cancer treatment, we can find that the tissue on the upper edge of the splenic artery is relatively loose, and the main vessel that may be encountered in the process of separation is the posterior gastric vessel, which has a thin diameter and can be directly dissected by ultrasonic knife. The dissection of the left gastric artery is equivalent to the release of the chain between the dorsal gastric tract and the diaphragmatic foot, which facilitates the exposure of the area around the common hepatic artery-an intrinsic hepatic artery and the left side of the portal vein and reduces the risk of bleeding.
Strategically, the lymph node dissection in front of the common hepatic artery (8a) and around the innominate hepatic artery (12a) should be placed at the end of the whole dissection procedure. Because lymph node dissection here is the most risky, it requires treatment of the right gastric vein, coronary vein, and involves separation of the anterior portal vein gap and protection of the common bile duct, and in case of accident it is likely to require intermediate open treatment. However, this site is located in the middle of the epigastrium and does not require a large incision for open treatment. The advantage of putting it at the end of the treatment is that the treatment of other sites has already been completed once open treatment is needed, and the advantages of lumpectomy have been brought into play. Personally, it is more convenient for the operator to stand on the right side of the patient during lymphatic dissection in groups 8a and 12a, mainly because the operation from the right lower abdominal puncture port facilitates the separation of the anterior portal vein gap and the operation within the hepatoduodenal ligament. The detachment of the duodenum facilitates the exposure of this area.
In conclusion, laparoscopic radical surgery for gastric cancer is a complex lumpectomy, and lymphatic dissection is its difficulty, mainly because the dissection process needs to span multiple surgical levels and requires the treatment of more complex vascular variants, and the risk of intraoperative bleeding is high. The bottom-up, left-to-right detachment step can help to better grasp the surgical level and effectively control the risk of intraoperative bleeding.