The Positional Relationship Between the Inferior Right Hepatic and Posterior Portal Veins

BACKGROUND: In anatomical segment 7 (S7) segmentectomy, the inferior right hepatic vein (IRHV) can be a useful landmark to identify the portal branch of segment 7 (P7); however, the positional relationship between the IRHV and the posterior portal branch has not been investigated. PATIENTS AND METHODS: We reviewed 203 patients who underwent preoperative multi-detector CT at Jichi Saitama Medical Center from 2022 to 2024. We processed 3D images and evaluated the running patterns concerning the IRHV, and the posterior portal vein and the right hepatic vein (RHV). The IRHV was classified as S6 (IRHV running inside S6 only), S7 (IRHV running inside S7 only), or S6/S7 (the vein courses along the intersegmental plane separating P6 and P7). RESULTS: IRHVs were present in 44.8% of patients and were classified as S6 in 11.0%, S7 in 17.6%, and S6/S7 in 71.4%. Among patients with IRHVs, 92.3% had either an IRHV or an RHV running along the intersegmental plane separating P6 and P7, compared with 24.1% of patients without IRHVs (p < 0.01). CONCLUSIONS: Most IRHVs were classified as S6/S7. When the IRHV does not serve as a landmark, the RHV may provide an alternative anatomical landmark for identifying P7 during anatomical S7 segmentectomy.