신장의 작동 원리: https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work 요로의 기능: https://www.urologyhealth.org/urologic-conditions/urinary-tract-problems 신장 및 요로 질환: https://www.kidney.org/atoz/content/kidneydiscauses