Colorectal Surgical & Gastroenterology Associates (CSGA). located in Lexington, Kentucky has a mission to provide you with the highest quality prevention, detection and treatment of digestive diseases in a caring, compassionate manner. Our team of board certified gastroenterologists (Stephen P. Schindler, MD - Nathan H. Massey, MD - Thomas C. Knopp, DO) and colorectal surgeons (John M. Fox ...Telehealth‧Colorectal Division‧Our Locations‧Colorectal Surgeons‧Our Physicians‧Gastroenterology.