Long descending lymphatic pathway from the pancreaticoduodenal region to the para-aortic nodes: its laterality and topographical relationship with the celiac plexus.

In 6 of 15 postmortem-treated cadaveric specimens, we found macroscopically thick lymphatic collecting vessels that originated from not only the nodes along the common hepatic artery (No. 8 nodes) but also from the pancreaticoduodenal region, and which drained directly into the para-aortic nodes immediately below the left renal vein (No. 16b1-inter or -latero nodes). The collecting vessels, if they originated from the ventral (dorsal) visceral side, passed to the left (right) of the superior mesenteric and celiac arteries. Moreover, the right-side vessels (5 specimens) were classified into superficial and deep courses to the celiac plexus, whereas they were superficial in the left side (2 specimens). One of the deep (right) courses continued to the thoracic duct without any intercalated nodes. In addition, another deep route drained into the para-aortic node immediately above the left renal vein (No. 16a2-inter node). We consider that these collecting vessels form "direct descending pathways" from the relatively peripheral lymphatics in the upper abdomen toward the thoracic duct origin. The pathway seems to be a collateral, or even major drainage route, and it appears responsible for skipped metastasis of primary cancer. Since the classical, limited entity of the intestinal lymph trunk does not coincide with our pathway, it should be reconsidered. The proposed entity of the direct, long descending pathway will influence the selection and modification of lymphadenectomy methods in cancer surgery in the pancreaticoduodenal region.