Retroportal lamina or mesopancreas? Lessons learned by anatomical and histological study of thirty three cadaveric dissections.

OBJECTIVE AND
BACKGROUND: Despite its importance in pancreatic head carcinoma, the retroportal lamina is still under studied, with only two anatomical cadaveric dissections in the English literature, with recent controversies about the concept of a mesopancreas.
METHODS: Resection of the mesopancreas was performed in 33 fresh cadavers. The pancreas and mesopancreas were separated from each other and the mesopancreas was immunohistochemically investigated.
RESULTS: The retroportal lamina is roughly rectangular in shape. Its dimensions are: height 6.2 cm (5-8), 2.5 cm wide (1.5-4). It contains a right hepatic artery arising from the superior mesenteric artery in 13.3% of cases. Microscopic examination revealed areolar tissue, adipose tissue, peripheral nerve, nerve plexus, lymphatics and capillaries. However, fibrous sheath and fascia were not found around these structures.
CONCLUSION: A right hepatic artery arising from the superior mesenteric artery is a frequent anatomic variation. Surgeons must be aware of this to ensure the integrity of the hepatic artery blood supply in patients treated by pancreaticoduodenectomy. Despite controversy about the reality of the mesopancreas (postulated in analogy to the mesorectum), because of the absence of fibrous sheath or fascia, its complete removal in pancreatic head carcinoma is feasible by a subadventitial dissection of the superior mesenteric artery which can be considered as the real limit of the mesopancreas.