Associated Gastroenterology Medical Group is the largest gastroenterology medical group in Orange County. Dr. Dennis Riff fo...unded the group in 1976. Dr. Steven Duckor and Dr. Michael DeMicco joined him the next year and have been practicing together since 1977. Presently, there are a total of six doctors working in the group. These include Drs. Riff, Duckor, DeMicco, Amer Rayyes, Kevin D....