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: Surgery
[{'content': "Most common cause of gangrene of foot of 30 years old farmer who is a chronic smoker - \nSelect and explain. \nA. Raynaud's disease, B. Myocardial infarction, C. Atherosclerosis, D. Thromboangitis obliterans", 'role': 'user'}, {'content': "Answer: D \nExplanation: All four can cause gangrene (Myocardial infarction can cause gangrene by thromboembolism)\nLets see, each option one by one.\n\nRaynauds disease \n\nIs ds of young women* (F:M ratio is 5:1)\ncommonly the upper limbs* are affected specially the fingers (the thumb is generally escaped)\nThe disease is characterized by Raynauds phenomenon* which is a series of attacks of\nLocal syncope → digits become cold and white*\nLocal asphyxia → digits turn blue with burning sensation*\nLocal recovery →digits regain normal colour*\n\n\nPulses remain unaffected* as this is the disease which affects arterioles\nWith the help of points (a) and (b) Raynauds ds can be ruled out.\n\nAtherosclerosis (Senile gangrene)\n\nSeen in elderly people over 50 years of age.\nThus because of age factor we can rule out atherosclerosis.\n\nMyocardial infaction\n\nAge factor again helps in ruling it out as MI is generally seen in elderly, though its incidence is increasing in young, but it cannot be a more common cause than Buerger's disease.\n\nBuerger's (Thromboangitis obliterans) \xa0Usual victims of this ds are young men below 40 yrs of age, who are smokers (ds is not seen in females and nonsmokers).\n\nBuerger ds is the inflammatory reaction in the arterial wall with involvement of the neighbouring vein and nerve, terminating in thrombosis of the artery.\nIt characterstically involves small and medium sized arteries (plantars, tibial and radial artery)\nBoth upper and lower extremities are affected.\nIn lower extremity the ds. occurs beyond the popliteal artery. In upper extremity the ds occurs beyond the brachial art.\nEarly in the course of Buergers ds the superficial veins are involved producing the characterstic migratory, recurrent superficial thrombophlebitis.\nAn imp difference with atheroselerosis is that, atherosclerosis is a disease of large sized arteries, buergers is a ds of small arteries.", 'role': 'assistant'}]