Hi Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern... Enlarged blood vessel in leg on one side should not be indicative of some major problem & may be caused due to many reasons as follow:- 1 Thrombophebitis - it is inflammation of vein which is caused due to thrombus formation or blood clotting. It is related to increased tendency for blood clotting, injury to vein wall, and reduced speed of blood in the veins such as varices and prolonged immobility 2. Varicose veins or defective valves in veins. As you have history of varicose veins, enlarged vein could be because of varicose vein related to defective valve. 3. Prolonged standing or sitting in same position may also cause enlargement of vein in leg 4. Other condition that may contribute in this problem include older age, pregnancy, obesity etc. I would suggest you taking following traetment -Wear compression stockings to decrease swelling. -Do not sit or stand for long periods. -Raise your legs above your heart three or four times a day for 15 minutes at a time. -Lose weight if you are overweight. Visit a physician if problem persists Hope this information helps