VARIATIONS IN LIVER VASCULAR ANATOMY AND IMPLICATIONS FOR HEPATECTOMY

Introduction: Variations in hepatic arterial and portal venous anatomy have previously been described; however, a comprehensive evaluation of hepatic vascular anatomy that includes other critical elements relevant to hepatectomy is lacking. We sought to characterize vascular variations and measurements that can inform surgical planning.

Methods: Patients who underwent hepatectomy (9/1/2021-12/31/2022) at our institution were identified. Included patients must have had a high-quality multiphasic, multidetector computed tomography scan of the abdomen and pelvis with intravenous contrast and axial cuts ≤3mm in thickness prior to any liver resections. Thorough evaluation of various aspects of hepatic artery (HA), portal vein (PV), and hepatic vein (HV) anatomy was performed. All measurements were made in millimeters. Patients who had anatomic distortions from large tumors were excluded from individual components as appropriate. Standard statistical methods were used for analysis.

Results: Of 390 patients, 209 (53.6%) were male, 254 (65.1%) were white, 70 (17.9%) were Hispanic, 32 (8.2%) were black, and 34 (8.7%) were of another race/ethnicity. Michels type 1 HA anatomy was present in 264 (67.7%) patients. The most common variant HA configurations were the presence of an accessory left HA in 47 (12.1%) and replaced right HA in 38 (9.7%) patients. The presence of variant HA anatomy did not differ significantly by sex or race/ethnicity. Among patients without aberrant right HA, the right HA coursed posterior to the common hepatic duct in 244 (75.5%), anterior in 73 (22.6%), and both posterior and anterior in 5 (1.5%). PV anatomy was Type A (standard) in 302 (77.4%), type B (PV trifurcation) in 40 (10.3%), type C (staged division – extrahepatic) in 43 (11.0%), and type D (staged division – intrahepatic) in 3 (0.8%) patients. PV anatomy did not differ significantly by sex or race/ethnicity. Among those with Type A anatomy, the median (interquartile range [IQR]) right PV length was 17.2 (11.4-21.8) mm; 57 (18.9%) patients had right PV length <10mm. A right inferior HV was present in 102 (26.2%) patients. Patients most commonly had 2 (N=144, 37.8%) or 3 (N=154, 40.4%) segment 5 and 8 tributaries (V5/V8) draining into the middle HV. The median (IQR) distance between the last V8 and middle HV-caval junction was 10.4 (4.5-19.6) mm; in 182 (47.8%) patients, this distance was <10mm. A common middle and left HV trunk was present in 245 (62.8%) and an accessory left HV was present in 65 (16.7%) patients.

Conclusion: Anatomic variations of the HA, PV, and HV are common and must be precisely defined with high-quality preoperative imaging in patients undergoing liver resections. Understanding and carefully assessing these vascular elements are critical to the safe performance of liver surgery.