THEORETICAL BACKGROUND FOR D2 GASTRECTOMY
Gastric cancer remains a major health problem in East Asia. In contrast, in the United States and Western Europe, the incidence of gastric cancer has declined but is often diagnosed at an advanced stage. Thus, the number of operations that a surgeon performs annually varies according to region, so it is not easy to define which type of gastric cancer surgery should be considered the global standard. Nevertheless, a consensus that D2 dissection is the most appropriate way to treat resectable advanced gastric cancer has been reached based on the results of long-term follow-up of the Dutch D1 versus D2 trial1 and the Japan Clinical Oncology Group (JCOG) 9501 study,2 which confirmed no survival benefit with more extensive lymphadenectomy.
Radical surgery for gastrointestinal cancer focused on en bloc removal of the primary tumor along with lymphovascular drainage by excising organ-specific mesenteries. This general concept is widely accepted in colorectal cancer surgery and is realized as total mesorectal excision (TME) or complete mesocolic excision (CME).3,4 D2 gastrectomy entails systematic dissection of all the nodes along the celiac axis (CA) and its named branches as well as the perigastric nodes. Based on embryologic principles, D2 gastrectomy is essentially a realization of mesentery-based surgery despite the anatomic restrictions inherent to the mesogastrium.5
UNIQUE ANATOMIC STRUCTURE OF THE MESOGASTRIUM
The basic technique of lymph node dissection is common for all gastrointestinal cancers. However, because of the high incidence of tumor deposits in the adipose tissue and significant tendency of developing peritoneal metastasis in gastric cancer, dissection without destroying the intact fascial package surrounding the fatty tissue where all nodes and tumor deposits are imbedded is of paramount importance.6 To perform a proper lymph node dissection of the stomach, an understanding of the unique anatomic structure of the mesogastrium is essential. The stomach has 2 mesenteries: the dorsal mesogastrium and the ventral mesogastrium. During the rotation of the intestinal system, the ventral mesogastrium becomes the lesser omentum and the dorsal mesogastrium becomes the greater omentum. The mesoduodenum and the transverse mesocolon are eventually overlaid by the greater omentum. The dorsal pancreas arises from the duodenal wall, grows into the mesoduodenum, and eventually extends into the dorsal mesogastrium. The anterior surface of the mesoduodenum is then overlaid by the proper transverse mesocolon and the greater omentum. These fetal events produce certain anatomic restrictions to conduct mesentery-based gastric cancer surgery. From the viewpoint of mesenteric structures, however, it is important to recognize that regional lymph node stations can be embedded in the dorsal or ventral mesogastrium, as shown in Figure 32-1A.
A. Development of omentum, mesogastrium, and mesoduodenum. Numbers in circles indicate lymph node stations according to the Japanese classification of gastric carcinoma. Blue nodes belong to the ventral mesogastrium, green nodes to dorsal mesogastrium, and yellow nodes to mesoduodenum. B. The simplified ...