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ANATOMICAL VARIATIONS OF LIVER SEGMENT 8: INSIGHTS INTO LATERAL EXTENSION AND VASCULAR IMPLICATIONS
Elena Panettieri
*1,2, William Kawahara
3, Etsuro Hatano
4, Satoshi Ogiso
4, Eduardo A. Vega
21Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Roma, Lazio, Italy; 2St. Elizabeth's Medical Center, Brighton, MA; 3Tufts Medical Center, Boston, MA; 4Kyoto Daigaku, Kyoto, Kyoto Prefecture, Japan
BACKGROUND: The intersegmental planes of the liver often deviate from the course of hepatic veins, challenging traditional anatomical definitions. This is particularly evident in segment 8 (S8), where the right hepatic vein (RHV) and the intersegmental border between segments 7 and 8 frequently do not align. This study aims to assess the volume of S8 protruding laterally beyond the RHV and its association with portal and venous anatomy.
METHODS: Imaging data from patients with healthy livers were collected at two high-volume hepato-biliary centers. Three-dimensional liver modeling and volumetric analysis were conducted using FUJIFILM SYNAPSE software to assess liver anatomy. S8 portal branching patterns were classified according to the Kokudo classification. S8 was further subdivided into dorsal, ventral, and lateral portions. The portion of S8 extending laterally beyond the RHV was defined as S8 lateral (Fig. 1). The anterior fissure vein (AFV) was defined as the vein that runs along the anterior fissure and primarily drains into the middle hepatic vein (MHV), occasionally into the RHV. The inferior right hepatic vein (IRHV) was identified as a tributary of the RHV draining segment 6. Subgroup comparisons were based on the median lateral S8 volume, with cut-offs derived from the cohort median. Statistical analyses were performed to evaluate the association between segment 8 lateral volume and the presence of IRHV and AFV dominance.
RESULTS: Of 94 patients included, 46.8% were male, with a median age of 49 years (IQR: 23-70) and a median BMI of 24.3 (IQR 21.7-27.0). The distribution of S8 portal branching patterns were as follows: A 55.3%, B 16.0%, C 17.0 %, and D 11.7%. The median total liver volume was 1323 cc (IQR 1098-1504) and the median right liver volume was 816 cc (IQR 697-974). The median volume of the antero-medial section was 449 cc (IQR 361-536) and the median segment 8 volume was 262.5 cc (IQR 213-342). The median volumes of S8 dorsal and ventral were 152 cc (IQR 104-199) and 110 cc (IQR 82-165). The median volume of S8 lateral was 53 cc (IQR 33-90), which represents 20.2% of the median S8 volume (Fig. 2). An IRHV and a dominant AFV were present in 43.0% and 57.4% of patients, respectively. When compared to patients with a S8 lateral volume ?53 cc, in those with a S8 lateral volume >53 cc a IRHV was lacking in 69.6% of cases (vs. 46.6%,
p=0.020), while the presence of a dominant AFV was similar in both populations (52.2% vs. 63.8%,
p=0.255). No differences were noted in terms of segment 8 portal branching between the two groups.
CONCLUSION: This study underscores the anatomical complexity and variability of S8, particularly its lateral extension beyond the right hepatic vein. These findings emphasize the importance of accounting for this portion of S8 during surgical planning to ensure complete drainage and avoid potential complications.
Figure 1: 3D reconstruction demonstrating the right hepatic vein, segment 8 of the liver, and the overlapping region with estimated volumes.
Figure 2. Bar plot of median segment 8 lateral volume compared to other liver volumes.
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