This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'A 70-year-old man has abdominal pain with mass in the abdomen. Angiography reveals aneurysm of the aorta.Most likely cause is - \nSelect and explain. \nA. Trauma, B. Atherosclerosis, C. Syphilis, D. Congenital', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Clinical\xa0 presentation of the abdominal aortic aneurysm\n\nEffects old person (>50 years), male > female.\nMost commonly asymptomatic and usually detected on routine examination as palpable, pulsatile non-tender mass.\nAs size increases pain may occur. Complications\nRupture into the peritoneal cavity and retroperitoneal tissues with massive, potentially fatal haemorrhage. The risk of rupture is directly related to the size of the aneurysm.\nObstruction of iliac, renal, mesenteric or vertebral branches due to direct pressure or narrowing of ostia → ischemic damage to respective organs.\nImpingement on adjacent structures e.g. compression of the ureter or vertebral erosion.\nEmbolism from atheroma or mural thrombus.', 'role': 'assistant'}]