Boundaries between subsegments IVa and IVb in the human liver

Until now there has been no definitive anatomical study of the boundary between hepatic subsegments IVa and IVb. In this study, we used a multicolor segmental corrosion cast technique and a multicolor segmental technique on plastinated slices, in combination with helical CT three-dimensional (3D) reconstruction on 15 donated fresh isolated human liver specimens. The corrosion cast technique was carried out on eight of these specimens, and the remaining seven livers were used to make horizontal plastinated slices. Examination of these specimens and observation of 20 additional liver corrosion cast specimens showed that all boundaries between hepatic segments were complex, undulating scissures rather than simple, flat planes. We also found that there was an obvious boundary between subsegments IVa and IVb, such that subsegment IVa laid posterosuperior to subsegment IVb. A tributary of a hepatic vein passed through the boundary between subsegments IVa and IVb, and could serve as an anatomical landmark of this boundary.