Rockford G. Yapp, MD Gastroenterology Doctor in Downers Grove, IL Leave a Review Dr. Rockford G. Yapp is Board Certified in Internal Medicine and Gastroenterology and has performed over 20,000 endoscopic procedures in his career. His training includes medical school at University of Nebraska Medical Center, with training at Cornell University, Cook County Hospital, Shiprock, … Continue reading Rockford G. Yapp, MD