Congenital absence of the portal vein with systemic diversion of mesenteric blood is extremely rare. We report a case of a congenital absence of the portal vein, accidentally discovered in a 59-year-old man, completely asymptomatic and not associated with other malformations or biochemical disorders. Ultrasonography imaging showed the absence of the portal vein and the distal tract of superior mesenteric and splenic veins draining together into a dilated left renal vein. Computed tomography and magnetic resonance confirmed the presence of a congenital portosystemic venous shunt and also revealed two hepatic arteries: one arising from the celiac trunk and the other from the superior mesenteric artery.