Hepatic vein anatomy of the medial segment for living donor liver transplantation using extended right lobe graft

Hepatic vein anatomy (V4) of the medial segment (S4) has been a matter of concern since introduction of extended right lobe (ERL) graft. To assess risk of hepatic venous congestion (HVC) in ERL donors, we tried to newly classify V4 anatomy. We analyzed V4 anatomy of 328 living donor livers by using 3-dimensional reconstruction (3-DR) and volumetry of computed tomography (CT). Variations of V4 were divided into type A (middle hepatic vein [MHV] dominant: n = 142, 43.3%), type B (MHV-dominant, but enabling preservation of dorsal V4 branch [V4b]: n = 40, 12.2%), type C (mixed: n = 92, 28%), and type D (left hepatic vein dominant: n = 54, 16.5%). We analyzed the amount of HVC at S4 in 143 donor livers of right lobe (RL) and ERL grafts. Occlusion of MHV trunk induced HVC equivalent to 85.2%, 85.4%, 55.2%, and 35.4% of S4 volume and 34%, 33.9%, 20.3%, and 14.2% of left liver volume in livers of types A, B, C, and D, respectively. Tailored V4b preservation reduced HVC significantly in type B livers. Considering that functional capability may be decreased in HVC portion, functional hepatic resection rate (FHRR) of ERL graft procurement ranged as follows: 62.3%-75% in type A, 62.2%-75% and 62.2%-68.7% in type B with and without V4b preservation, respectively; 63.2%-70.7% in type C; and 61.8%-67.2% in type D. These results support the theory that these categories of V4 types are closely correlated with potential amount of HVC at S4, reflect the possibility of V4b preservation, and are compatible with CT findings. We believe that this V4 classification is applicable to assess donor V4 anatomy in practice.