A gastroenterologist is a physician who specializes in disorders and conditions of the gastrointestinal tract. Most gastroenterologists are board-certified in this subspecialty. After completing the same training as all other physicians, they first complete at least two years of additional training in order to attain board certification in internal medicine, then gastroenterologists study for an additional 2-3 years to train specifically in conditions of the gastrointestinal tract.