Analysis of technical pathways for laparoscopic gastric cancer surgery

Since Goh et al. applied laparoscopic technology to radical gastrectomy in 1997, after more than 10 years of accumulation, laparoscopic radical gastrectomy has become technically mature. However, due to the complexity of anatomy and technical operation, the clinical popularity of laparoscopy in radical gastrectomy is far less than laparoscopic colon surgery. The complexity of laparoscopic radical gastrectomy is mainly due to the following reasons:

1) The anatomical levels of radical gastric cancer surgery are complex, spanning multiple anatomical levels from the lower pancreatic area, the anterior pancreatic area to the upper pancreatic area. Unlike colorectal surgery, the entire surgical separation process, whether in the abdominal or pelvic part, is unified within a single fascial level, namely, Toldt's and presacral spaces.

2) Gastric regional lymph nodes are distributed along the blood vessels around the stomach, pancreas, and bile duct. These structures need to be properly protected and not damaged. In the radical treatment of colorectal tumors, the regional lymph nodes are cleared by directly cutting off the blood vessels from the root and removing them together. For example, in the radical treatment of rectal cancer, the inferior mesenteric artery is freed from the root and the lymph nodes around the blood vessels are cleared.

3) Digestive tract reconstruction after radical resection of gastric cancer requires more complex laparoscopic surgical techniques.

In principle, laparoscopic technology is only a technical means and does not change the principles of surgical treatment. In order to better carry out laparoscopic radical resection of gastric cancer, it is necessary to conduct a more in-depth analysis of the basic principles and surgical anatomy of radical resection of gastric cancer, and make necessary adjustments according to the characteristics of laparoscopic technology. The radical resection of gastric cancer is the same as the radical resection of other digestive tract tumors, requiring the en bloc resection of the tumor and regional lymph nodes. The standard clearance range for radical resection of gastric cancer is D2 clearance. Radical resection of gastric cancer by open surgery has proven that it is technically feasible to remove the stomach and the lymph nodes in the region in one piece while ensuring D2 clearance. Its specific strategy (taking total gastrectomy as an example) can be roughly summarized as follows:

1) From bottom to top. That is, starting from separating the gastrocolic ligament, separating upward along the fused fascial gap between the dorsal gastric mesocolon and the transverse colon mesocolon, and then processing the subpyloric area (the 6th group of lymph nodes) after reaching the lower edge of the pancreas, and then crossing the pancreatic surface to reach the upper pancreatic area to clear the 5th, 7th, 8th, 9th, and 11th groups of lymph nodes. The separation order from bottom to top can gradually free the stomach and continuously expose the relevant areas.

2) Three regions, three levels. In the dissection process from bottom to top, the separation steps can be roughly divided into the lower pancreatic region, the anterior pancreatic region and the upper pancreatic region. The three regions are separated at different levels and have different anatomical landmarks. The pancreas is located in the center of the three regions.

In the lower pancreatic region, after opening the gastrocolic ligament, the separation plane enters the fused fascial space between the greater omentum and the transverse mesocolon. This space is avascular and is located in front of the middle colic vein. During the separation process along the surface of the blood vessel to the root of the transverse mesocolon and the lower edge of the pancreas, the superior mesenteric vein and Henle's trunk are exposed, and the separation plane enters the deep surface of the pancreatic (posterior) fascia. Embryologically, the anterior and posterior pancreatic fascia originate from the posterior layer of the dorsal gastric mesocolon and fuse with the anterior lobe of the transverse mesocolon below the pancreas. Separation along Henle's trunk close to the pancreas to the right can expose the right gastroepiploic vein and then the right gastroepiploic artery, and the separation plane turns from the deep surface of the pancreatic (posterior) fascia below the pancreas to the deep surface of the pancreatic capsule in front of the pancreas between the anterior pancreatic fascia and the pancreatic proper fascia.

In the anterior region of the pancreas, the gastroduodenal artery is the main landmark for separation. The posterior part of the duodenal bulb can be freed by separating upward along this blood vessel. The pancreatic capsule is also lifted up along with the anterior lobe of the transverse colon mesentery until the upper edge of the pancreas reaches the upper region of the pancreas.

The upper pancreatic region is the most difficult part of lymph node dissection for radical treatment of gastric cancer. On the one hand, there are important blood vessels such as the celiac trunk, hepatic artery, splenic artery, posterior gastric vessels, and coronary veins, which make it easy to bleed during separation; on the other hand, separation of this area requires crossing the dorsal gastric mesentery and entering the Toldt's space located in the shallow part of the prerenal fascia on its deep surface. Dissection upwards in this space can reach the posterior part of the gastric cardia and expose the left and right diaphragmatic crus.

From the inferior pancreatic region to the anterior pancreatic region, and then from the anterior pancreatic region to the superior pancreatic region, there is a process of crossing anatomical levels, and the process of crossing anatomical levels is accompanied by the processing of blood vessels and the clearance of lymph nodes. In other words, lymph node clearance for radical treatment of gastric cancer requires dissection and separation at the non-fascial level. This is why radical treatment of gastric cancer is more difficult than radical treatment of colorectal cancer. Between the inferior pancreatic region and the anterior region, the blood vessels are disconnected, so there is no problem of vascular protection, but between the anterior pancreatic region and the superior pancreatic region, lymph node clearance needs to be performed under the premise of protecting the blood vessels, so the space around the blood vessels constitutes an important level and path.

3) Vascular pathway. In the above three areas and the corresponding three separation levels, blood vessels are important anatomical landmarks. In the lower pancreatic region, the vascular landmark is the middle colic vein-superior mesenteric vein-Henle's trunk, and in the anterior pancreatic region, the vascular landmark is the gastroduodenal artery. The significance of these two blood vessels is to guide the correct anatomical level. The vascular landmark of the upper pancreatic region is the celiac trunk and its branches: the common hepatic artery-proper hepatic artery, and the splenic artery. These blood vessels are the objects that need to be protected and the boundaries of lymph node clearance. Therefore, lymph node clearance in the upper pancreatic region is the difficulty and focus of radical treatment of gastric cancer. The lymph nodes in the upper pancreatic region are distributed along the celiac trunk-hepatic artery-proper hepatic artery-splenic artery. To clear the lymph nodes, they must be separated along these arteries.

Another object involved in the vascular pathway is the portal vein. In the hepatoduodenal ligament, the portal vein is located behind the proper hepatic artery. At the upper edge of the pancreas, the bifurcation of the common hepatic artery and the gastroduodenal artery just crosses the beginning of the portal vein. In order to reduce the risk of portal vein bleeding, the portal vein can be dissected from below the hepatic artery-gastroduodenal artery and the upper edge of the pancreas before the lymph node dissection around the hepatic artery, and then the anterior portal vein space can be separated toward the portal part. The significance of the separation of the anterior portal vein space is to determine the posterior limit of the lymph node dissection around the hepatic (proper) artery, which is conducive to improving the safety of the operation.

Appendix: Dissection steps of the area above the pancreas:

1. Dissect along the upper edge of the pancreas to expose the hepatic artery, gastroduodenal artery, and proper hepatic artery, and then expose the celiac trunk and splenic artery. In this process, attention should be paid to the right gastric vein, coronary vein, and posterior gastric vessels. These vessels run perpendicular to the common hepatic artery or splenic artery, and can merge into the splenic vein in front of or behind it. The slightest carelessness can cause bleeding. The requirement for separation is to reach the loose space behind the pancreas at the splenic artery, and the common hepatic artery must be completely free.

2. Expose the portal vein. The common hepatic artery and the gastroduodenal artery form an arch at the upper edge of the pancreas. There is a loose connective tissue gap between the lower edge of this arch and the upper edge of the pancreas. Careful separation can directly reach the surface of the starting part of the portal vein. Blunt dissection along the surface of the portal vein into the hepatoduodenal ligament can completely open the tissue gap in front of the portal vein. Generally, there will be no blood vessels in front of the portal vein. After completing the above two steps, there will be a safe limit for lymph node clearance at the upper edge of the pancreas, above the pylorus, and in the hepatoduodenal ligament, and the thoroughness and safety of lymph node clearance will be guaranteed.

3. Expose the diaphragmatic crus, open the hepatogastric ligament along the lower edge of the liver to the right edge of the cardia, and start to separate the anterior and posterior layers of the hepatogastric ligament at the right edge of the cardia. The anterior layer becomes the serosa in front of the cardia, and the posterior layer becomes the serosa on the surface of the gastropancreatic fold on the posterior wall of the lesser omental sac. There is a clear boundary between the right side of the gastropancreatic fold and the diaphragmatic crus. By opening the serosa here and performing blunt separation, all the fat lymphatic tissue behind the stomach under the cardia can be separated from the diaphragmatic crus. Its anatomical level should be continuous with the Toltd's space in front of the left prerenal fascia. Exposure of the diaphragmatic crus can also start from the left side, mainly for total gastrectomy with spleen preservation, that is, when the splenogastrostomy ligament is separated to the left side of the cardia, the gastrodiaphragmatic ligament is opened, the left diaphragmatic crus is exposed first, and then separated to the left.

4. Open the serosa on the surface of the hepatoduodenal ligament along the right side of the gastroduodenal-hepatic artery toward the liver hilum, skeletonize the hepatic artery, and clear the lymph nodes around the hepatic artery. The rear boundary of the clearance is the space in front of the portal vein, and the right boundary is the common bile duct. Pull the cleared tissue to the left and expose the portal vein. Then, clear from the top to the bottom along the left edge of the portal vein from the liver hilum, and then turn to the upper part of the common hepatic artery and the gastropancreatic fold, and merge the separation surface with the separation surface in front of the left diaphragmatic crus, and then further clear the lymph nodes around the celiac trunk and cut off the left gastric artery.

The biggest advantage of the above-mentioned cleaning procedure is that groups 12a, 8a, 7, 9, and 11 lymph nodes can be removed in one piece together with groups 1, 3, and 5 lymph nodes and the lesser curvature of the stomach.

The above points are an anatomical analysis of the surgical path based on the principles of oncological treatment of gastric cancer. They are not only applicable 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 path. First, the limitations and characteristics of the laparoscopic perspective require different exposure strategies during surgery and appropriate adjustments to the surgical steps. Secondly, laparoscopic surgery has high requirements for bleeding control. Bleeding that may not be serious during open surgery may lead to surgical conversion under laparoscopy, which puts higher technical requirements on the anatomical separation of related steps.

In terms of surgical exposure, the laparoscope's viewing angle radiates from the umbilicus to the surrounding areas, and the exposure of the entire surgical process should be carried out around this viewing angle. The bottom-up steps of open abdominal radical treatment of gastric cancer just meet this requirement, but it needs to be adjusted in the left-right direction. Looking at the surgical videos of domestic and foreign experts and our experience, taking right-handed surgeons as an example, the surgeon stands on the left side of the patient, and the separation sequence from the left to the right through the left upper abdominal puncture is more in line with the principles of ergonomics. In this way, during the separation of the gastrocolic ligament and the dissection of the lower and upper edges of the pancreas, the viewing direction and the separation surface are vertical, and the viewing angle and the operating lever always present a good angle.

In the radical resection of gastric cancer, the risk of bleeding mainly exists in two parts. The first is during the exposure of the subpyloric gastrocolic trunk and the treatment of the right gastroepiploic vein. The vein here is relatively thin and easily ruptured, and there are many anatomical variations, which is the first difficulty in laparoscopic radical resection of gastric cancer. The second is the upper edge of the pancreas and the left side of the hepatoduodenal ligament. The bleeding here mostly comes from the right gastric vein, coronary vein and posterior gastric vein. The location of these veins is uncertain, deep, and closely related to the portal vein. Improper treatment can easily lead to failure and conversion of the operation.

In my personal experience, whether in the subpyloric area or in the suprapancreatic area, the left-to-right dissection strategy is conducive to the prevention of bleeding. Under the pylorus, use the middle colic vein as a guide to first separate toward the surface of the superior mesenteric vein at the lower edge of the pancreas. No obvious blood vessels will be encountered in this process. After reaching the lower edge of the pancreas, do not rush to separate to the right. You can first free the gap behind the duodenal bulb close to the pancreas, and then carefully dissect to the right to expose the gastrocolic trunk and the right gastroepiploic vein. When freeing the right gastroepiploic vein, be alert to the anterior superior pancreaticoduodenal vein that may flow in from the back. The specific strategy is not to get too close to the pancreas during separation, and wait until the gap behind it is freed before approaching the root of the right gastroepiploic vein.

At the upper edge of the pancreas, the strategy of going from left to right is also beneficial for the prevention of bleeding. We can start by exposing the splenic artery, then move upward into the space in front of the prerenal fascia and expose the left diaphragmatic crus, and then gradually expose the left gastric artery and treat it. From the intraoperative observation of radical resection of gastric cancer, we can find that the tissue at the upper edge of the splenic artery is relatively loose, and the main blood vessels that may be encountered during the separation process are the posterior gastric vessels, which have a thinner diameter and can be directly cut off with an ultrasonic scalpel. During the separation of the upper edge of the splenic artery, it is easy to enter the space in front of the prerenal fascia, and then expose the left diaphragmatic crus and treat the left gastric artery. The separation of the left gastric artery is equivalent to removing the chain between the dorsal gastric mesentery and the diaphragmatic crus, which is conducive to the exposure of the area around the common hepatic artery-proper hepatic artery and the left side of the portal vein, reducing the risk of bleeding.

From a strategic point of view, the lymph nodes in front of the common hepatic artery (8a) and around the proper hepatic artery (12a) should be cleared at the end of the whole clearing process. Because the risk of lymph node clearing here is the greatest, it is necessary to deal with the right gastric vein and coronary vein, and it involves the separation of the space in front of the portal vein and the protection of the common bile duct. If an accident occurs, it is likely to require conversion to laparotomy. However, this part is located in the middle of the upper abdomen, and laparotomy does not require a large incision. The advantage of putting it last is that once laparotomy is required, the treatment of other parts has been completed, and the advantages of laparoscopic surgery have been brought into play. In my personal experience, it is more convenient for the surgeon to stand on the right side of the patient during lymph node clearing in groups 8a and 12a, mainly because the operation from the right lower abdominal puncture port is conducive to the separation of the space in front of the portal vein and the operation within the hepatoduodenal ligament. The division of the duodenum is conducive to the exposure of this part.

In short, laparoscopic radical resection of gastric cancer is a relatively complex laparoscopic surgery, and lymph node dissection is its difficulty. The main reason is that the dissection process needs to span multiple surgical levels and needs to deal with more complex and variable blood vessels. The risk of intraoperative bleeding is very high. Successful laparoscopic radical resection of gastric cancer depends on a deep understanding of the anatomical levels and vascular variations around the stomach. The separation steps from bottom to top and from left to right are conducive to a better grasp of the surgical levels and effectively control the risk of intraoperative bleeding.