The Characteristics of Right Hepatic Vein in Middle Hepatic Vein Dominant Type, and the Variation of Glissonian Pedicle at Left Lobe of the Liver, Using Cadaver Liver Dissection

Abstract

Introduction: Many liver resection and liver transplantation surgeries are performed worldwide, and clinical outcomes have recently improved. Studies of liver anatomy have developed alongside clinical and technical achievements as these types of research complement each other. I intended to evaluate some controversies for liver anatomy, using cadaver dissection. For right hemiliver, I tried to evaluate the relation of right hepatic vein (RHV) and middle hepatic vein (MHV) because right lobe of the liver has been mainly used as a graft in living related donor liver transplantation. For left hemiliver, I had two concerns. The first one was to evaluate the feasibility of the 'isolated IVb (inferior) resection of the liver'. The second aim was to define the border between left medial section and left lateral section. Unexpectedly, I found 'new Glissonian pedicles (GPs)' between the two sections, and I also discussed whether or not the portal vein branches (P4d) in ‘Nagino’s trisectionectomy’ are related with the 'new GPs'.

Methods: For right hemiliver study, I dissected ten adult cadavers from April to July 2012. I defined the types of MHV and RHV according to their characteristics of the branches which drain the segments of the right hemiliver. I evaluated which type of MHV matched which type of RHV, and identified whether accessory right hepatic vein (ARHV) exist in what match of MHV and RHV.

For isolated IVb resection in left hemiliver, I dissected ten adult cadavers from May 2004 to June 2004. I followed the definition that IVa is superior portion of IV segment, and that IVb is inferior portion of IV segment. I measured the numbers of Glissonian pedicles (GPs) in IV segment, IVa, and IVb, respectively as well as the distances between the origin of IVa branches and IVb.

For border between left medial section and left lateral section study, from April 2012 to July 2012, 31 adult cadavers were delicately dissected simultaneously from the visceral (inferior) and diaphragmatic (superior) surfaces. We defined a ‘NewGP’ as an extra GP other than the traditional GPs, which supply segments II, III, IVa, and IVb in the ordinary direction, and anatomically located superior to the umbilical fissure (UF). We subdivided ‘NewGPs’ into ‘II NewGPs,’ ‘III NewGPs,’ ‘IVa NewGPs,’ ‘IVb NewGPs,’ and ‘central NewGPs’ (neutral to the traditional GP) according to the distance from the origin of the traditional GP.

Results: For right hemiliver study, MHV type A (MHV dominant) was 3/10 (30%), type B was 3/10 (30%), and type C was 4/10 (40%). RHV type A was 2/10 (20%), type B was 6/10 (60%), type C was 1/10 (10%), and type D was 1/10 (10%). In MHV dominant type A, RHV type B was 2/3, and type C was 1/3. ARHV existed in 3/3 (100%) for MHV dominant type A, and ARHV existed only in 1/4 (25%) for MHV type C.

For isolated IVb resection study in left hemiliver, the numbers of GPs in IV segment was 5 (±1.3) in on average, 4 to 7. The mean numbers of GPs in IVa was 1.6 (±0.7), from 1 to 3. The numbers of GPs in IVb was 3.4 (±0.9), from 2 to 5. There were 2 cases which were considered as having their common origin because the distance between the origins of IVa and IVb were very close.

For border between left medial section and left lateral section study, the umbilical fissure vein (UFV) was identified in 83.8% of cases. The UFV mainly drained into the left hepatic vein (LHV), with an incidence of 88.5%. The incidence of drainage into the MHV was 3.8%, and independent drainage from the LHV or MHV was identified in 7.6% of cases. The incidence of ‘NewGPs’ was 30/31 (96.8%). Of them, ‘central NewGPs’ were most prevalent, with an incidence of 28/31 (90.3%). The diameter of the ‘NewGPs’ ranged from 3.5 mm to 5.6 mm, which was not significantly different from that of traditional GPs (II-, III-, or IV-GP).

Conclusions: For right hemiliver study, the incidences of MHV type and RHV type were much different from the previous reports. The characteristics of ARHV according to MHV and RHV type were also from the other articles. It could be furtherly evaluated with much more numbers of cadaver dissection or using modernized three-dimensional imaging technique.

For isolated IVb resection study in left hemiliver, one of important points in this study is that two of ten cases (20 %) had common origin of IVa and IVb. In case of 'IVb + IV resection', which is commonly performed for patients with gallbladder cancer. When we clamp temporarily IVb segment-looking GPs originating from UF and some portion of IVa discolors as well as IVb segment, I believe we have to ligate selectively IVb segment GP because it should mean common origin of IVa and IVb segment.

For border study between left medial section and left lateral section, we believe that ‘central NewGPs’ together with the UF can serve as a new border between the left medial section and lateral section. In addition, we think that the P4d in ‘Nagino’s trisectionectomy’ corresponds to the ‘IVa NewGP’ in our study. The role of the ‘NewGP’ would be to complement the traditional II, III, IVa, and IVb pedicles in supplying the liver. When liver surgeons face the liver malignancy of IV or II/III segment superficially invading over the umbilical fissure, I believe that they can secure the needed margin resecting the area supplied by 'NewGP'. It could prevent from expanding the surgery in patients whose liver function is poor or marginal.