Configuration of the right portion of the caudate lobe with special reference to identification of its right margin

The configuration of the right portion of the caudate lobe (CL), and especially the exact location of its right margin, remains obscure. This study aimed to identify this right margin according to reliable landmarks suitable for use during clinical examinations and surgery: (1) the bifurcation of the right portal vein, (2) the end of the right hepatic vein, and (3) the notch on the gallbladder fossa. The plane defined by these three landmarks is called the right paracaval plane. Dissection of 55 livers demonstrated that the entire CL was usually contained within the left half of the specimen after cutting along the right paracaval plane (Type A: 65.4%, 36/55). However, its right portion sometimes extended beyond this plane into the right half of the liver (34.6%, 19/55), forming one or two islands when viewed from the paracaval plane (Types B and C). We found two separate marginal configurations among the 19 rightward extensions of the paracaval portion: a tree-like, deep protrusion (11/19) and a relatively smooth border (8/19). The present results suggest the existence of reliable landmarks that will allow a right-side limit for surgical resection of the CL to be established: (1) the right paracaval plane (60% reliability), (2) 10 mm to the right of the plane, including the terminal of the right hepatic vein (80% reliability), and (3) the widest margin, including the 30 mm to the right of the right paracaval plane, the right side running along the inferior vena cava, and the diaphragmatic surface around the end portions of the three main hepatic veins (100% reliability).