Veins are blood vessels that transport blood from your organs, muscles, and other body tissue to your heart. They have a valve inside to prevent blood flow and pooling. Due to blockage, they may lead to swollen and twisted veins, called varicose veins, and they can happen in both men and women. When to see a Vascular Doctor? If you find the following sign and symptoms, you should visit your doctor to know the proper treatment for your issue.