A 45-year-old woman is admitted to the emergency department with a complaint of severe abdominal pain. CT scan and MRI examinations reveal a tumor of the head of the pancreas involving the uncinate process. Which of the following vessels is most likely to be occluded?

The superior mesenteric artery arises from the aorta, deep to the neck of the pancreas, then crosses the uncinate process and third part of the duodenum. An uncinate tumor can cause compression of the superior mesenteric artery. The common hepatic artery arises superior to the body of the pancreas and is unlikely to be affected by a tumor in the uncinate region of the pancreas. The cystic artery and vein, supplying the gallbladder, are also superior to the pancreas. The inferior mesenteric artery arises at the level of L3, which is thus situated deep to and inferior to the head of the pancreas. The portal vein, formed by the confluence of the superior mesenteric vein and splenic vein, passes deep to the neck of the pancreas.