Dear sir i can understand your concern in my opinion removing legs due to gangrene is the last treatment. doctors will take that decision only when the infection is causing trouble to other organs and in toxic shock kind of conditions. the legs are removed still we can have better life with regular physiotherapy and artificial limb support in some condition when limbs are removed they may gain excess of weight due to lack of exercise. usually neck veins give us good accesses during hospital stay when ever hospital based dialysis is planned in emergency manner there is nothing to fell bad taking neck vein access is better than peripheral veins in terms of response. Regards Dr vamsi