As has already been described in the Chap. 1, since the concept of the surgical trunk by Gillot [1] (Fig. 6.1) was first introduced in Japan in the 1970s, two main views are prevalent with regards to lymph node dissection for right colon cancer. Namely, lymph node dissection of the main lymph node based on the dominant artery root and lymph node dissection of the surgical trunk based on the lymph flow of Gillot [2]. No definitive conclusions have been reached as to which is more correct; however, the former calls for the dissection of portions where the lymph flow is missing, while in the latter the theory of lymph flow is only emphasised and whether the dissection of all this part is actually clinically meaningful has not been determined.

As for the configuration of the right colon, it can be considered as divided into a simple fusion fascia between the colon and retroperitoneum at the caudal side (Fig. 6.2) and a relatively confused fusion fascia at the cranial pancreatoduodenal portion (Fig. 6.3). In the former, the right colon and retroperitoneum are fused to become the right fusion fascia of Toldt and the ascending colon is buried in the retroperitoneum (Fig. 6.2a, b). In the latter, it is easy to understand the fascial composition if the embryologic processes are divided into two stages (Fig. 6.3a, b). That is, the second portion of the duodenum that was accompanied by a dorsal mesentery falls to the right, forming the posterior pancreatic fascia of Treitz between the parietal peritoneum and the pancreatoduodenal region (Fig. 6.3c). Then, the ascending colon covers the head of the pancreatoduodenal region when the intestinal rotation is completed, and it forms the right fusion fascial of Toldt and the anterior pancreatic fascia (Fig. 6.3e). In other words, the right fusion fascia of Toldt is divided into the posterior pancreatic fascia of Treitz dorsally and the anterior pancreatic fascia ventrally at the margin of the second portion of the duodenum (Fig. 6.3e). Additionally, the hepatic flexure is located at the transition of the transverse colon with the mesocolon and the ascending colon, in which the mesocolon is fused with the posterior abdominal wall.

In addition, with regards to the relation between the transverse colon and the second portion of the duodenum, three fusion patterns can be considered in three degrees of fusion. That is, there are fusions between the ventral leaf of the transverse colon and about half of the second portion of the duodenum (Fig. 6.4a), between the ventral leaf of the transverse colon and the entire second portion of the duodenum (Fig. 6.4b), and almost no fusion (Fig. 6.4c)

In order to dissect the right colon from the pancreaticoduodenum, the relationship between the anterior pancreatic fascia, the posterior pancreatic fascia of Treitz, and the right fusion fascia of Toldt, and between the transverse mesocolon and the anterior pancreatic fascia must be considered. In right colon cancer, in order to dissect the colon from the retroperitoneum, it is necessary to dissect between the right fusion fascia of Toldt and the deep subperitoneal fascia. However, since the right colon is depressed on its dorsal side compared with the left colon, the lateral approach of the right colon tends to be a difficult and uncertain procedure (Fig. 6.2b). The right fusion fascia of Toldt is close to the deep subperitoneal fascia in the paracolic gutter of the lateral of the ascending colon (Fig. 6.2b). Thus, if one attempts to dissect the colon from this side, there is a tendency to enter the dorsal side of the deep subperitoneal fascia, and place the urinary tract and the spermatic vessels on the discharge side, and be in danger of lifting the right kidney. In contrast, it is easier to dissect between the right fusion fascia of Toldt and the deep subperitoneal fascia along the mesenteric root because this region is rich in fat and connective tissue (Fig. 6.2b I, II). In addition, since the deep subperitoneal fascia in the pancreaticoduodenal section continues onto the dorsal side of the posterior pancreatic fascia of Treitz behind the pancreas head, dissection of the right colon from the dorsal side is easy provided that the ventral side of the deep subperitoneal fascia is maintained (Fig. 6.3e). As the dissection is continued using this approach, the right colon can be dissected freely without any damage to the other organs because the urinary tract and the spermatic vessels are now located on the dorsal side of the deep subperitoneal fascia. From the above discussion, it can be deduced that laparoscopic right colectomy is recommended to be performed using the medial-retroperitoneal approach.

The medial-retroperitoneal approach that precedes the dissection between the right fusion fascia of Toldt and the deep subperitoneal fascia is a basic procedure. This surgical procedure takes advantage of laparoscopic surgery as it may be easier to dissect the colon from the retroperitoneum and this may mobilise the colon earlier.