[Chicago Gastroenterology | Chicago GI | Samuel F. Castillo, MD Samuel Castillo, Sr. MD Doctor Samuel F. Castillo of Arlington Gastroenterology Specialists is a board certified, spanish speaking gastroenterologist and GI Specialist, dedicated to excellence in gastroenterology specializing in upper GI endoscopy, colonoscopy and hemorrhoids treatment. He is a medical doctor serving the communities of Arlington Heights, Palatine, Mount Prospect, Des Plaines, Wheeling, Buffalo Grove, Schaumburg, Hoffman Estates, and Elk Grove Village.]