Dr. Nielsen practices phlebology in Sioux City, Iowa. He is a diplomate of the American Board of Phlebology and is also board certified in general surgery by the American Board of Surgery and in cardiothoracic surgery by the American Board of Thoracic Surgery. He is a Fellow of the American College of Surgeons and the American College of Phlebology and is a member of the the Society of Thoracic Surgeons. He is a Registered Vascular Technologist by the American Registry for Diagnostic Medical Sonography (ARDMS). Dr. Nielsen practiced general surgery for three years and cardiothoracic and vascular surgery for seventeen years prior to dedicating his practice to the treatment of venous disease.