上腸間膜動脈から直接分岐する右結腸動脈が2本存在し，そのいずれもが上腸間膜静脈の背側を走行した上行結腸癌の1例

A case of ascending colon cancer with two right colonic arteries branching directly from the superior mesenteric artery, both of which ran dorsal to the superior mesenteric vein

◆要旨：右側結腸の手術は左側に比べ血管分岐バリエーションが多い．今回，上腸間膜動脈（SMA）から分岐する右結腸動脈（RCA）を2本認め，いずれも上腸間膜静脈（SMV）背側を走行する稀な症例を経験した．症例は75歳，女性．上行結腸癌に対しロボット支援結腸右半切除術・D3郭清を施行した．回結腸動脈（ICA）はSMV腹側を走行し，SMAから分岐するRCAを2本認め，いずれもSMV背側を走行していた．SMAから分岐するRCAの頻度は25〜43％と報告されているが，2本分岐する例は稀であり，頻度やSMVとの位置関係は明らかでない．今後，3Dで安定した視野展開が得られるロボット支援手術の普及により外科的解剖の理解がより深まることが期待される．

　Surgery on the right side of the colon has more vascular branching variations than surgery on the left side, which influences the degree of surgical difficulty. We experienced a rare case in which two right colonic arteries（RCAs） branched directly from the superior mesenteric artery（SMA），both crossing dorsal to the superior mesenteric vein（SMV）．The patient was a 75-year-old female. She underwent robot-assisted right hemicolectomy and D3 dissection for ascending colon cancer. The ileocecal artery（ICA） crossed ventral to the SMV, and two RCAs branched off the SMA, both crossing dorsal to the SMV. The frequency of RCA branching directly from the SMA is reported to be 25-43％, but cases with two RCA branches are rare. Furthermore, in terms of the location of the ICA and RCA in relation to the SMV, it has been reported that it is rare for both the ICA and RCA to cross dorsal to the SMV. Therefore, the vascular branching in this case is extremely rare. In the future, it is hoped that the understanding of surgical anatomy will be further deepened through the spread of robot-assisted surgery, which allows for the stable development of a 3D field of view.