Effect of Tranilast on restenosis of Arteriovenous Fistulas for Hemodialysis

INTERVENTION: It is the crossover trials which is receving tranilast for one year and non‐medication for one year. It is the crossover trials which is receving tranilast for one year and non‐medication for one year. CONDITION: hemodialysis patients PRIMARY OUTCOME: The primary outcome is number of PTA times for one year after patients receive tranilast. SECONDARY OUTCOME: The secondary outcome is failure of the fistula or graft determined by ultrasound. INCLUSION CRITERIA: The patients who visit our hospital at regular intervals and undergo PTA are recruited.