The resective procedure can be carried out by an en bloc or separating technique.
Systematic lymphadenectomy can start with dissection of lymph nodes at the hepatoduodenal ligament or in the area of the gastroduodenal artery. Then the right gastric artery must be identified and ligated at its origin.
Lymphadenectomy is continued along the common hepatic artery at the upper border of the pancreas towards the celiac axis; on the way, the left gastric vein has to be divided.
To perform total gastrectomy, the greater omentum ( including the anterior sheet of the mesocolon ) is dissected completely; in subtotal distal gastrectomy, the greater omentum is partially resected. In this way the right gastroepiploic vessels are separated and ligated at the gastroduodenal artery including lymph node dissection in the infrapyloric region.
As the next step the left gastric artery can be radicularly ligated at the celiac axis. If an accessory left hepatic artery has been identified in the lesser omentum, the root of the left gastric artery is preserved and performing lymph node dissection along this artery only the branches ascending to the lesser curvature of the stomach are ligated.
Lymphadenectomy continues in the proximal directions toward the right paracardiac lymph node group 1 (right crura of the diaphragm) in front of the anterior surface of the aorta.
Then the lymph nodes along the splenic artery towards the splenic hilus are dissected (without performing splenectomy).
The en bloc dissected specimen now can be elevated to remove the retrogastric and left paracardial lymph nodes.
In the case of subtotal distal gastrectomy, the same procedure can be carried out - after dividing the phreno-esophageal ligament, the right paracardial nodes can be dissected completely. Lymph nodes 2 and 4a at the greater curvature in the area of the fundus are only partially dissected.
D2 lymphadenectomy can be extended in gastric carcinomas located in the distal or upper-third of the stomach.
In the antral carcinomas lymph node dissection should be performed along the hepatoduodenal ligament and behind the head of the pancreas (nodes 12 and 13) together with the right paracaval nodes.
According to the retroperitoneal location of the cardia and posterior surface of the fundus, lymphatic drainage is directed to the retroperitoneal lymph nodes and those at the hilus of the spleen. Therefore in carcinomas of the upper third of the stomach lymphadenectomy should be extended to the left para-aortic nodes towards the left renal vein. Furthermore pancreas preserving splenectomy with radicular ligation of the splenic artery should be carried out
( 1 ).
Lee et al underline that the incidence of metastases to the splenic hilar lymph nodes has been reported to be around 10% in proximal gastric cancer. Lymph node metastases in gastric cancer has a strong correlation with the depth of tumor invasion.
In early gastric cancer splenectomy should not be performed because lymph node metastases is not found in the splenic hilum; the 5 year survival rate of patients with EGC is significantly higher in the spleen preserved group. However in advanced gastric cancer the effect of splenectomy on the prognosis is controversial. The authors conclude that splenectomy in gastric cancer surgery has no influence on the long-term surgical outcome of patients in terms of postoperative recurrence and prognosis for gastric cancer. Therefore splenectomy for the purpose of lymph node dissection should not be mandatory and surgeons should consider spleen preservation in gastric cancer patients who have no definite splenic hilar lymph node enlargement or any direct invasion to the spleen
( 2 ).
Following these guidelines, systematic lymph node dissection includes compartments I (1 through 6 perigastric lymph nodes ), II (nodes 7 through 11) and occasionally III (nodes 13,14, and 16).
To ensure exact pathohistological examination the stomach has to be opened along the greater curvature directly after resection. The specimen then can be fixed with pins to a cork plate to complete the documentation of tumor parameters begin the pathological workup.
Based on anatomical and histopathological examinations, an average of at least 25 to 27 lymph nodes can be worked up in D2-resection with complete dissection of compartments I and II. This number can be increased to 43- an average following D3 lymphadenectomy including lymph nodes 12 through 16. These results are guideline for quantity and quality control because the number of lymph nodes does not change independent of the extent of metastases or tumor stage. Nevertheless according to the actual TNM classification a minimum of 15 lymph nodes has to be dissected and histologically examined to describe an exact pN or pN0 category
( 1 ).
References
1) HJ Meyer, J.Jahne. Lymph node dissection for gastric cancer. Seminars in Surgical Oncology 1999; 17:117-124.
2) K Y Lee et al. Impact of splenectomy for lymph node dissection on long term surgical outcome in gastric cancer. Annals of Surgical Oncology 2001, 8 (5): 402-406.
