Gastroenterology Institute of Southern California Stresses the Importance of Routine Colonoscopy : Check out the client testimonials section of the Gastroenterology Institute of Southern California’s website. See what real people have to say about Dr. Peyton Berookim, MD and his friendly staff of professionals. Client testimonials are the most trustworthy method in researching anything nowadays. Dr. Berookim cares about his patients, and he runs his practice around the philosophy that people’s health should be a doctor’s number one priority. His conscientious practice reflects his attention to detail during procedures and every other step of the medical process.