桑山 美知子¹, 竹内 和男², 鶴岡 尚志¹, 井上 淑子¹, 城山 昌代¹, 鶴 千津¹, 中西 成元¹

Michiko KUWAYAMA¹, Kazuo TAKEUCHI², Naosi TSURUOKA¹, Yoshiko INOUE¹, Masayo SHIROYAMA¹, Chizu TSURU¹, Shigemoto NAKANISHI¹

¹虎の門病院臨床検査室, ²虎の門病院消化器科

¹Department of Clinical Physiology, Toranomon Hospital, ²Department of Gastroenterology, Toranomon Hospital

キーワード : Ultrasonography, Branching pattern of the portal vein, Anomalous branching pattern , Right-sided umbilical portion

The branching patterns of the portal vein (PV) in the hepatic hilum were studied with ultrasonography (US) in 1,025 healthy subjects.
The most common branching patterns seen were the two-branch type, the three-branch type, and the independent posterior-branch type, these were seen in 78.5, 12.0 and 8.4% of the subjects, respectively.
Anomalous branching patterns were also noted in 11 subjects (1.1%). They were divided into two types. In Type A branching patterns, the base of the right anterior branch formed the umbilical portion (UP) of the portal vein. In Type B patterns, the right anterior branch originated in the normal UP of the left hepatic lobe. Type A branching patterns were found in 7 patients (0.7%), and Type B patterns were found in 4 (0.4%).
The Type A anomalous UP, which is considered to be embryologically derived from the first branch of the right umbilical vein rather than the left, has been named "right-sided UP".
In 6 of the 7 subjects with "right-sided UP" branching, the body of the gallbladder (GB) was situated just beneath the round ligament. In 3 of these, the fundus of the GB was positioned to the left of the round ligament.
Because anomalous branching of the portal vein is relatively common in the hepatic helum, it is important to check for this anomaly with an ultrasound examination before hepatic or biliary surgery.