[The mesoduodenum].

In the present study an anatomical examination of ten bodies was made to describe the fixation of duodenum and pancreas to the posterior abdominal wall. It has become apparent that the shape of the posterior mesoduodenum of the first part of duodenum is rodlike. Due to the secondary retroperitoneal fixation between duodenum and pancreas a vascularized, wide-based borderline lamella remains in the area of second and third parts of the duodenum. The borderline lamella corresponds to the tela subserosa and strengthens Treitz fascia and Gerota fascia in the prerenal area. It covers the inferior vena cava, and is fixed to the adventitia of the abdominal aorta. The retroduodenopancreatical tissue forms a duodenopancreatical layer which contains its own vessels. Now it is possible to understand better the surgical importance of pancreatitis, retroduodenal haematoma and mobilization of duodenum and pancreas.