Portal vein branching order helps in the recognition of anomalous right-sided round ligament: common features and variations in portal vein anatomy

Purpose This study aimed to evaluate the common features and variations of portal vein anatomy in right-sided round ligament (RSRL), which can help propose a method to detect and diagnose this anomaly. Methods In this retrospective study of 14 patients with RSRL, the branching order of the portal tree was analyzed, with special focus on the relationship between the dorsal branch of the right anterior segmental portal vein (P A–D ) and the lateral segmental portal vein (P LL ), to determine the common features. The configuration of the portal vein from the main portal trunk to the right umbilical portion (RUP), the inclination of the RUP, and the number and thickness of the ramifications branching from the right anterior segmental portal vein (P A ) were evaluated for variations. Results In all subjects, the diverging point of the P A–D was constantly distal to that of the P LL . The portal vein configuration was I- and Z-shaped in nine and five subjects, respectively. The RUP was tilted to the right in all subjects. In Z-shaped subjects, the portal trunk between the branching point of the right posterior segmental portal vein and that of the P LL was tilted to the left in one subject and was almost parallel to the vertical plane in four subjects. Multiple ramifications were radially distributed from the P A in eight subjects, whereas one predominant P A–D branched from the P A in six subjects. Conclusions Based on the diverging points of the P A–D and P LL , we proposed a three-step method for the detection and diagnosis of RSRL.