“…1,[6][7][8]10 In many previous literature, configurations of the retroperitoneal planes have been analyzed by using cadaveric models and investigating the distribution of the thickened fascial planes and fluid collections in patients with retroperitoneal pathologies. 1,3,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] However, there have been only two previous literature regarding the medial pathways of the right retromesenteric plane. 3,9 The right retromesenteric plane separating the anterior pararenal space from the perirenal space is thought to be composed of the left leaf of the primary mesocolon, primary parietal peritoneum and anterior renal fascia in front of the right kidney, and the right leaf of the primary mesoduodenum, primary parietal peritoneum and anterior renal fascia behind the pancreatic head and descending duodenum ( Figure 1).…”