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': 'A patient presented with local gigantism of the leg and increased pulsations of the lower limb veins. Most probable diagnosis is : \nSelect and explain. \nA. Tumor, B. AV fistula, C. Varicose veins, D. Incompetence of the saphenofemoral junction', 'role': 'user'}, {'content': "Answer: B \nExplanation: The patient is having congenital AV fistula which has caused overgrowth of the leg.\nArteriovenous fistula (AVF) \n\nAVF may be congenital or acquired (by the trauma of a penetrating wound, or surgically created for renal dialysis)\nStructural effect on veins → Veins are arterialised*, they become dilated tortuous and thick walled.\nPhysiological effects of fistula -\nIncreased pulse pressure (Increased systolic & decreased diastolic)\nEnhanced venous return result in Increased HR* and Increased CO*.\nLeft ventricular enlargement and later cardiac failure may occur\nA congenital fistula in the young may cause overgrowth of limb*.\nIn the leg, indolent ulcers may result* from relative ischemia below the short circuit.\n\nClinical signs\n\nA pulsatile swelling*\nA thrill on palpation*\nContinuous bruit on auscultation*\nNicoladonis sign' or Branham sign* → Pressure on the artery proximal to fistula causes the swelling to diminish in size, a thrill or bruit to cease, the pulse rate to fall and the pulse pressure return to normal.", 'role': 'assistant'}]