Which of the following statement(s) is/are true concerning the arterial venous anatomy of the liver?

b.Most frequently, the entire length of each hepatic vein is within the parenchyma of the liver

c.A replaced right hepatic artery may be placed in jeopardy during performance of a pancreaticoduodenectomy

There are three major hepatic veins which carry blood from the central veins of the hepatic substance to the inferior vena cava (IVC). In two-thirds of patients, there is a single large right hepatic vein which joins the right anterior wall of the IVC and a middle and a left hepatic vein which converge one-to-two cm from the IVC and enter the left anterior wall of the IVC as a single vessel. In one-third of patients, each major hepatic vein joins at the same horizontal level of the IVC as a separate trunk. In some patients, there is a short but definable extraparenchymal segment of one or more of the hepatic veins at the confluence with the IVC. More frequently, the entire length of the hepatic veins is intraparenchymal, which may preclude early, safe hepatic venous isolation during hepatic resection. There is considerable variability in the origin and course of the right and left hepatic arteries. The most common finding (55% of patients) is a transverse common hepatic artery from the celiac trunk which gives off the gastroduodenal, right gastric, and supraduodenal arteries and courses obliquely in the left anterior aspect of the hepatoduodenal ligament as a proper hepatic artery. After giving off the cystic artery to the gallbladder, there is then a fairly low trifurcation into a single right, middle, and left hepatic arteries. Knowledge of the most common variations is extremely importance since inadvertent division may occur during gastric, pancreatic, and hepatobiliary procedures. There may be a replaced or accessory left hepatic artery which arises from the left gastric artery and courses transversely in the lesser omentum. With nearly equal frequency, there is a replaced or accessory right hepatic artery from the superior mesenteric artery near its origin which courses posterior or through the head of the pancreas obliquely along the right posterior border of the hepatoduodenal ligament. Although original anatomic descriptions deny the existence of collateral vessels to the opposite hepatic lobe, image perfusion studies after ligation of main or replaced hepatic arteries have clearly demonstrated the presence of collateral flow to the deprived lobe.