The details of the surgical procedures are shown in the Supplementary material video. Briefly, patients were first placed in the Trendelenburg position, after which five trocars were inserted (infraumbilical area: 10 mm optic, right lower quadrant: 5 mm, right upper quadrant: 5 mm, left upper quadrant: 10 mm, left lower quadrant: 5 mm). Carbon dioxide was inflated through the intraumbilical trocar, and the pressure was maintained at 15 mmHg. The operating surgeon stood on the patient's left side, with the assistant on the right.
The first step was cephalic dissection, which was the separation of the midgut and foregut, i.e., the separation of the right-side mesocolon from the greater omentum, the mesogastrium, and dorsal mesoduodenum. The extra-omentum approach was preferred, and the greater omentum was selectively preserved because the serosa was not invaded. The dissection plane between mesogastrium and continuous mesentery of the gastric-transverse colon was entered and extended, and the upper mesogastrium and the inferior transverse mesocolon were left intact and smooth (Fig. 1A). And then, the dissection continued downward to the right side of descending duodenum along the mesocolic space between the mesocolon and dorsal mesoduodenum (Fig. 1B). Therefore, the dorsal mesogastrium, transverse mesocolon, and dorsal mesoduodenum were intact.
The second step was the dorsal separation, which included the separation of the midgut and hindgut. After exposing the dorsal aspect of the Treitz ligament, the fusion fascia between the mesointestin and the dorsal right-side mesocolon was separated along the superior aspect of the Treitz ligament (Fig. 1C). And then, the dissection continued upward to the right side of descending duodenum along the mesenteric fused fascia space between the prehypogastric nerve fascia and mesocolon. (Fig. 1D), and the duodenum and its dorsal mesentery were revealed. Further cephalad separation along the dorsal mesentery of the duodenum was performed, naturally extending to the continuous dorsal mesentery of the duodenum-pancreas. Finally, the dorsal dissection met with cephalic dissection. Therefore, the lower prehypogastric nerve fascia, middle mesoduodenum, upper mesopancreas, and right-side mesocolon were intact.
The third step was ventral dissection. A sloping natural fold can be identified by traction to the ileocolic vessels, dissection was performed along the mesenteric fused fascia between the small intestinal and right hemicolon. Finally, the ventral dissection met with dorsal dissection.
The fourth step involved the ligation of intra-mesenteric vessels and the separation of right-side mesocolon from left-side mesocolon. Intra-mesenteric vessels were defined and located within the fused fascia or mesocolic space, which are ligated along the mesenteric fused fascia space regardless of their name (Fig. 1E), and the vascular sheath of the superior mesenteric vein is not damaged. And then, the right-side mesocolon was separated from the left-side mesocolon along the mesocolic space (Fig. 1F), En-bloc resection of the right hemicolon and its mesentery is performed.