Origin of the thoracic duct and pancreaticoduodenal lymphatic pathways to the para-aortic lymph nodes.

We investigated the afferent and efferent connections of the para-aortic lymph nodes (group 16 nodes) relative to the origin of the thoracic duct in 85 postmortem cadavers. The origin was usually restricted to groups 16b1-inter and -latero nodes (type I; 90.6%), regardless of whether the union of their efferents occurred at the abdominal or thoracic level. We also occasionally observed thick collecting vessels originating from the dorsal aspect of the pancreaticoduodenal region, running along the right side of and superficial to the celiac plexus and emptying into group 16b1 nodes. The thoracic duct originated occasionally not only from group 16b1 nodes but also from group 16a2 nodes (type II; 9.4%). Moreover, in all 85 specimens, the group 16a2-inter node often received afferents from the celiac plexus itself or the tight connective tissue between the plexus and diaphragmatic crus, or both. The results support the reliability of the extended D2 lymphadenectomy (D2 + group 16b1 nodes + group 16a2-inter node) for curative cancer surgery in the pancreaticoduodenal region.