He is double board certified by the American Board of Surgery in surgery and surgical critical care. Dr. Thiessen's expertise includes trauma surgery,surgical critical care, acute care surgery, and general surgery. He is a member of AmericanCollege of Surgeons, American Medical Association,and Surgical Critical Care Medicine. Dr. Thiessen received his medical degree from theUniversity of Iowa. He completed his residency at Dignity Health St. Joseph's Hospital and Medical Center and then completed a fellowship in trauma surgical critical care at the University of California San Francisco, Fresno.