This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pancreas, Subject name: Surgery
In carcinoma head of pancreas, nausea and vomiting is due to: 
Select and explain. 
A. External compression of duodenum, B. Poal vein infiltration, C. Proliferation infiltration of tumor into duodenum, D. Chemotherapy related
A: External compression of duodenum
Answer: A: External compression of duodenum 
Explanation: Depending upon the location of the tumor, the symptoms may vary. - Periampullary carcinoma - at the ampulla; most common symptom is Jaundice. - Carcinoma at the head of pancreas - External compression of duodenum , compression of bile duct; most common symptom is jaundice. - Carcinoma at the body or tail of pancreas - asymptomatic at early stages. Most common symptom at later stages is weight loss. Due to involvement of retroperitoneal nerve plexus, there is abdominal pain. - When malignancy advances and infiltrates the 2nd pa of duodenum, it causes nausea, vomiting or gastric outlet obstruction.