As the director of the inflammatory bowel disease (IBD) Center he has expertise in diagnosing and treating IBD, Crohn's disease, colitis, and celiac disease. Dr. Mattar has a particular interest in IBD therapeutics and IBD and colorectal cancer prevention. He is active in clinical research and medical education for trainees, the community, and patients. Dr. Mattar sees patients in his gastroenterology practice at MedStar Georgetown University Hospital. He embraces a holistic approach to patient care within the IBD Center at MedStar Georgetown as part of a multidisciplinary treatment team that includes dietitians and other key providers. He is also active in clinical trials for IBD and performs fecal microbiota transplantation for recurrent and refractory C. difficile infection. Dr. Mattar teaches at MedStar Georgetown University Hospital as Associate Professor of Medicine, and is the Director of the Fellowship Training Program in Gastroenterology. He is also an active member of the mission committee of the Crohn's and Colitis Foundation, DC. Metro chapter; the ACG Training Committee and the Patient Education National Scientific Advisory Committee for the Crohn’s and Colitis Foundation. In 2014, Dr. Mattar was recognized by the American Gastroenterological Association's Bridges to Excellence Program for his commitment to providing comprehensive quality care for patients with IBD.