1. Gastrointestinal Section, Department of Internal Medicine, VA North Texas Healthcare System, Dallas, Texas, USA;
2. Department of Gastroenterology, University of Florida at Jacksonville, Jacksonville, Florida, USA;
3. Department of Clinical Science, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA;
4. Division of Hematology-Oncology, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA;
5. Medical Service, VA North Texas Health Care System, Dallas, Texas, USA;
6. Division of Gastroenterology, University Of Texas Southwestern Medical Center, Dallas, Texas, USA