Since Goh et al. applied laparoscopic techniques to radical gastric cancer surgery in 1997, after more than 10 years of accumulation, laparoscopic radical gastric cancer treatment has become technically mature. However, due to the complexity of anatomy and technical operation, the clinical popularity of laparoscopy in radical gastric cancer treatment is still far less than that of laparoscopic colon surgery. The complexity of laparoscopic radical gastric cancer surgery is mainly due to the following reasons.
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 anatomically, unlike in colorectal surgery where the entire surgical separation process is within a single fascial level, i.e., Toldt’s and anterior sacral hiatus, 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 treatment of 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 to make necessary adjustments according to the characteristics of laparoscopic techniques. Like the radical treatment of other tumors of the digestive tract, gastric cancer requires whole-block resection of the tumor and regional lymph. The standard clearance range for radical gastric cancer surgery is D2 clearance. Radical treatment of gastric cancer with open surgery has proven that it is technically safe and feasible to remove the entire stomach and the lymph nodes in the region to which it belongs while ensuring D2 clearance. The specific strategy (using total gastrectomy as an example) can be summarized as follows.
1) From the 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 14thv lymph nodes and the subpyloric region (group 6 lymph nodes), and then crossing the surface of the pancreas to the suprapancreatic region to clear the 5th, 7th, 8th, 9th, and 11thp group 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 along the surface of this vessel toward the root of the transverse colonic mesentery and the lower edge of the pancreas, 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 subsequently the right gastroretinal artery, while the level of separation shifts from the deep pancreatic (posterior) fascia below the pancreas to the deep pancreatic envelope anterior to 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, left gastric artery, 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 Toldt’s hiatus, which is located deep in the superficial 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 an anatomical level crossing from the inferior to the anterior pancreatic region and then from the anterior to the superior pancreatic region, and the process of anatomical level crossing is accompanied by the treatment of blood vessels and lymph node dissection. In other words, lymphatic clearance in radical gastric cancer treatment 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-superior mesenteric vein-Henle’s trunk, and in the anterior pancreatic region the vascular landmark is the gastroduodenal artery, both of which are significant in leading to the correct anatomical level. The vascular landmarks in the suprapancreatic region are the celiac 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 of radical surgery for 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 limit of periportal lymphatic clearance of the hepatic (innominate) artery, which helps to improve the safety of the procedure.
Steps of dissection of the suprapancreatic region.
1. Dissect along the superior margin of the pancreas to reveal the hepatic artery – gastroduodenal artery – intrinsic hepatic artery, and later to reveal the celiac trunk – splenic artery. In this process, attention should be paid to the right gastric vein, coronary vein and posterior gastric vessels, the course of these vessels is perpendicular to the common hepatic artery or splenic artery, which can converge into the splenic vein either in front of it or behind it, and a slight inadvertence can cause bleeding. The requirement of separation at the splenic artery is to reach the pancreas The separation of the splenic artery should reach the lax gap behind the pancreas, while the common hepatic artery should be completely free.
2. Reveal the portal vein. The common hepatic artery and the gastroduodenal artery form an arch at the upper edge of the pancreas, and there is a loose connective tissue gap between the lower part of this arch and the upper edge of the pancreas, so careful separation can 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 blunt dissection along the surface of the portal vein toward the hepatoduodenal ligament, and there are usually no vessels converging in front of the portal vein. After the above two steps are completed, the lymphatic clearance in the superior margin of the pancreas, the pylorus, and the hepatoduodenal ligament has a safe boundary, and the thoroughness and safety of lymphatic clearance is guaranteed.
3, reveal the foot of the diaphragm, open the hepatogastric ligament along the lower edge of the liver to the right edge of the cardia, and begin to separate the anterior and posterior layers of the hepatogastric ligament 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 plasma membrane on the surface of the gastro-pancreatic fold in the posterior wall of the small omental sac. There is a distinct boundary between the right side of the gastro-pancreatic fold and the foot of the diaphragm, and 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 anatomic level when continued with the Toltd’s gap anterior to the left anterior renal fascia. Exposure of the diaphragmatic foot can also be started from the left side, mainly for total gastrectomy with preservation of the spleen, i.e., the gastro-diaphragmatic ligament is opened when the splenogastric ligament is separated to the left side of the cardia, and the left diaphragmatic foot is exposed first and then separated to the left.
4. Open the plasma membrane on the surface of the hepatoduodenal ligament along the right side of the gastroduodenal-intrinsic hepatic artery toward the hilar, skeletonize the intrinsic hepatic artery, and clear the lymph nodes around the intrinsic hepatic artery, with the posterior limit of the clearance being the anterior hilar space and the right limit being the common bile duct. The cleared tissue is held to the left and the portal vein is revealed, and then cleared from above along the left margin of the portal vein, starting from the porta hepatis, and then moving to the top of the common hepatic artery and the gastro-pancreatic folds, and converging the detached surface with the detached surface in front of the left diaphragmatic foot, and then further clearing the lymph nodes around the abdominal trunk and dissecting the left gastric artery.
The greatest advantage of the above-mentioned sweeping steps is that groups 12a, 8a, 7, 9, and 11 lymph nodes together with groups 1, 3, and 5 lymph nodes and gastric lesser curvature tissue can be removed in whole.
The above points are based on the anatomical analysis of the surgical pathway based on the oncological principles of treatment of gastric cancer and should be equally applicable not only to open surgery, but also to laparoscopic surgery. However, due to the characteristics of laparoscopic surgery, some details need to be adjusted in the process of implementing the above mentioned path. First, the limitations and characteristics of the laparoscopic view require a different exposure strategy during the procedure and appropriate adjustments to the surgical steps. Second, laparoscopic surgery requires a high level of bleeding control, and bleeding that may not be serious in open surgery may lead to a mid-operative turn in laparoscopy, which places a higher technical requirement on the anatomical separation of the relevant steps.
In terms of surgical exposure, the view of the lumpectomy 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 surgery 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 in line with the principles of human efficacy for the right-handed surgeon, for example, with the operator standing on the left side of the patient, through the left upper abdominal puncture port. In this way, during the separation of the gastrocolic ligament, the dissection of the inferior and superior 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 radical gastric cancer surgery, the risk of bleeding mainly exists in two areas, one is during the exposure of the subpyloric gastrocolic trunk 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 difficulty in lumpectomy gastric cancer surgery. Secondly, the upper margin of the pancreas and the left side of the 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 the failure and mid-operation.
Personally, I experience 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. Using the mesocolic vein as a guide in the subpyloric region, first separate towards the surface of the superior mesenteric vein at the lower edge of the pancreas, a process that does not encounter obvious vessels. After reaching the inferior margin of the pancreas, it is important not to rush to the right, but to 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. It can be started by exposing the splenic artery, then moving upward into the anterior gap of the anterior renal fascia and exposing the left phrenic foot, followed by progressive exposure and treatment of the left gastric artery. From the intraoperative observation, 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 during the separation process is the posterior gastric vessel, which has a thin diameter and can be directly dissected with the ultrasonic knife, and during the separation process of the upper edge of the splenic artery, the anterior renal fascial space can be easily accessed, and then the left diaphragmatic foot can be exposed and the left gastric artery can be treated. 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, requires the treatment of more complex vascular variants, and carries a high risk of intraoperative bleeding. The bottom-up, left-to-right detachment step helps to better grasp the surgical level and effectively control the risk of intraoperative bleeding.