69.下圖為上腹部超音波影像,箭號所指的低回音圓形構造為何?
(A)左腎靜脈(left renal vein)(B)上腸繫膜動脈(superior mesenteric artery)(C)上腸繫膜靜脈(superior mesenteric vein)(D)脾動脈(splenic artery)