Providers

Our Providers are all Board Certified
At Gastroenterology Specialist, our board certified providers are committed to compassionate, personalized care. By utilizing years of experience and the latest technology, our providers deliver fast, accurate, and comprehensive diagnosis and treatment.

 

John R. Hood, MD

Dr. John Hood joined Gastroenterology Specialists, Inc. in 1986. He is board certified in gastroenterology and internal medicine and is a member of the American College of Gastroenterology.

Before joining GSI, Dr. Hood served as Chairman of the Endoscopy Lab and the Department of Medicine at St. Francis Hospital and as an associate professor of clinical medicine at the University of Oklahoma in Tulsa.

Board Certification: 

American Board of Internal Medicine, Gastroenterology, 1989
American Board of Internal Medicine, Internal Medicine, 1987

Education:

The University of Oklahoma, Oklahoma City, OK – MD, 1982

Oral Roberts University, Tulsa, OK – BS, 1976

Professional Training:

American College of Gastroenterology – Fellow, 1997

University of Oklahoma, Oklahoma City, OK – Gastroenterology Fellowship, 1985-1987

University of Oklahoma Tulsa Medical College, Tulsa, OK – Internal Medicine Residency, 1985

 

Michael J. Martin, MD
Dr. Michael Martin joined Gastroenterology Specialists, Inc. in 1994. He has been board certified in Gastroenterology since 1994 and was board certified in internal medicine in 1992. He is a member of the Arkansas/Oklahoma Endoscopic Society.

Dr. Martin has special interests in the management of a wide array of gastrointestinal disorders and colon cancer prevention. He has served as Chief of Gastroenterology and Endoscopy at St. Francis Hospital and as an associate professor of clinical medicine at the University of Oklahoma in Tulsa. He has been involved in medical missions and various volunteer efforts.

Board Certification:

American Board of Internal Medicine, Gastroenterology, 1994
American Board of Internal Medicine, Internal Medicine, 1992

Education:

University of Texas Health Science Center, San Antonio, TX – MD, 1989

University of Texas, Austin, TX, – BBA, 1983

Professional Training:

University of Texas Health Science Center, MD Anderson, Houston, TX – Gastroenterology Fellowship, 1992-1994

University of Oklahoma Health Science Center, Tulsa, OK – Internal Medicine Residency, 1989-1992

 

William K. Briggs, MD

Dr. William Briggs joined Gastroenterology Specialists, Inc. in 2000. He is board certified in gastroenterology and internal medicine.

Before joining GSI, Dr. Briggs was a resident physician at Hillcrest Medical Group and the University of Oklahoma College of Medicine in Tulsa, Oklahoma. He also served as Assistant Clinical Professor in the Department of Internal Medicine at the University of Oklahoma College of Medicine in Tulsa.

Board Certification:

American Board of Internal Medicine, Gastroenterology, 1997
American Board of Internal Medicine, Internal Medicine, 1995

Education:

University of Oklahoma College of Medicine, Tulsa, OK – MD, 1990

University of Oklahoma, Norman, OK – BS, 1984

Professional Training:

Louisiana State University, Baton Rouge, LA – Gastroenterology Fellowship, 1994-1996

University of Southern California, Downey, CA – Hepatology Fellowship, 1993-1994

University of Oklahoma College of Medicine, Tulsa, OK – Internal Medicine Residency, 1993

 

Jeffrey L. Bigler, MD

Dr. Jeffrey Bigler joined Gastroenterology Specialists, Inc. in 2003. He is board certified in gastroenterology and internal medicine and is a member of the American College of Gastroenterology and the American Society for Gastrointestinal Endoscopy.

Dr. Bigler is primarily interested in inflammatory bowel disease, colon cancer screening, IBS, and functional abdominal pain and has a special interest in the psychological aspects of GI disorders.

Board Certification:

American Board of Internal Medicine, Gastroenterology, 2003

American Board of Internal Medicine, Internal Medicine, 2000

Education:

University of Oklahoma College of Medicine, Tulsa, OK – MD, 1997

Southwest Baptist University, Bolivar, MO, – BS, 1993

Professional Training:

University of Missouri-Columbia, Columbia, MO – Gastroenterology Fellowship, 2000-2003

University of Oklahoma college of Medicine, Tulsa, OK – Internal Medicine Residency, 2000

 

Sheldon C. Berger, DO

Dr. Sheldon Berger joined Gastroenterology Specialists, Inc. in 2007. He is board certified in gastroenterology and internal medicine and is a member of AOA, ACOI, OOA, ASGE, ACG, and TOMS.

Before joining GSI, Dr. Berger was the president of Green Country Gastroenterology. He has practiced at numerous hospitals and is a published author with the Journal of Cellular Physiology.

Board Certification:

American Osteopathic Board of Internal Medicine, Gastroenterology, 1991
American Osteopathic Board of Internal Medicine, Internal Medicine, 1990

Education:

University of Health Sciences, College of Osteopathic Medicine, Kansas City, MO – DO, 1984

University of Kansas, Lawrence, KS – BS, 1978

Professional Training:

Chicago Osteopathic Hospital System, Chicago, Illinois – Gastroenterology and Hepatology Fellowship, 1988-1990

Tulsa Regional Medical Center, Tulsa, OK – Internal Medicine Residency, 1988

Tulsa Regional Medical Center, Tulsa, OK – Internship, 1985

 

David W. Morris, DO

Dr. David Morris joined Gastroenterology Specialists, Inc. in 2007. He is board certified in gastroenterology and internal medicine, is a fellow of the American College of Osteopathic Internists, and is a member of AOA, ACOI, OOA, and TOMS. He is the medical director of Healthcare Research Consultants and is a constant participant in multidisciplinary clinical medical research.

Dr. Morris is active in local and international medical mission work. Before joining GSI, he was a gastroenterologist with Green Country Gastroenterology, an internal medicine physician with Internal Medicine Consultants, and the associate director of medical education with Tulsa Regional Medical Center.

Board Certification:

American Osteopathic Board of Internal Medicine, Gastroenterology, 1995
American Osteopathic Board of Internal Medicine, Internal Medicine, 1992

Education:

Oklahoma State University, College of Osteopathic Medicine, Tulsa, OK – DO, 1986

Oklahoma State University, Stillwater, OK – BS, 1982

Professional Training:

Chicago College of Osteopathic Medicine – Olympia Fields, IL – Gastroenterology Fellowship, 1992-1994

Tulsa Regional Medical Center, Tulsa, OK – Internal Medicine Residency, 1990

Tulsa Regional Medical Center, Tulsa, OK – Rotating Internship, 1987

 

Roy L. Thompson, MD

Dr. Roy Thompson joined Gastroenterology Specialists, Inc. in 2009. He is board certified in gastroenterology and internal medicine and is a member of the American Gastroenterology Association and the American Society for Gastrointestinal Endoscopy.

Before joining GSI, Dr. Thompson was a gastroenterology physician with Warren Clinic in Tulsa, Oklahoma.

Board Certification:

American Board of Internal Medicine, Gastroenterology, 2008
American Board of Internal Medicine, Internal Medicine, 2004

Education:

University of Oklahoma, Oklahoma City, OK – MD, 2001

University of Oklahoma, Norman, OK – BS, 1997

Professional Training:

University of Tennessee, Memphis, TN – Gastroenterology Fellowship, 2005-2008

University of Tennessee, Memphis, TN – Internal Medicine Chief Resident, 2005

University of Tennessee, Memphis, TN – Internal Medicine Residency, 2007

University of Tennessee, Memphis, TN – Internal Medicine Internship, 2004

 

Geoffrey A. Fillmore, DO

Dr. Geoffrey Fillmore joined Gastroenterology Specialists, Inc. in 2011. He is board certified in gastroenterology and internal medicine and is a member of the American Society for Gastrointestinal Endoscopy, the American College of Gastroenterology, and the American Gastroenterology Association.

Dr. Fillmore completed extensive training in endoscopic ultrasound (EUS). He currently performs endoscopic ultrasounds in hospital settings. He is a published author with Practical Gastroenterology and Obesity Surgery.

Board Certification:

American Board of Internal Medicine, Gastroenterology, 2011
American Board of Internal Medicine, Internal Medicine, 2007

Education:

Oklahoma State University College of Osteopathic Medicine, Tulsa, OK – DO, 2004

University of Central Oklahoma, Edmond, OK – BS, 2001.

Professional Training:

Scott & White Hospital, Temple, TX – Gastroenterology Fellowship, 2008-2010

Scott & White Hospital, Temple, TX – Internal Medicine Chief Residency, 2008

Scott & White Hospital, Temple, TX – Internal Medicine Residency, 2007

Scott & White Hospital, Temple, TX – Internal Medicine Internship, 2005

 

Zena A. Roz, RDN/LD

Zena Roz joined Gastroenterology Specialists, Inc. in 2016. She is a Registered Dietitian Nutritionist by the Commission on Dietetic Registration, licensed by the Oklahoma Board of Medical Licensure, and is a member of the Academy of Nutrition and Dietetics.

Zena has a special interest in gastroenterology disorders and their relationship with nutrition. She is passionate about healthy eating, fitness, weight loss, and disease prevention. She believes a well-balanced diet combined with regular physical activity is the foundation of good health.

Board Certification:

Registered Dietitian Nutritionist, Commission on Dietetic Registration, 2016

Licensed Dietitian- 2185, Oklahoma Board of Medical Licensure, 2016

Education:

University of Oklahoma College of Allied Health, Oklahoma City, OK- BS, Nutritional Sciences, 2016

Professional Training:

Hillcrest Medical Center, Tulsa, OK- Clinical & Management Rotation 2015-2016

Peggy and Charles Stephenson OU Cancer Center, Oklahoma City, OK- Community Rotation 2016

Oklahoma Heart Hospital South Cardiac Rehab, Oklahoma City, OK- Community Rotation 2016

Huston Huffman Fitness Center, Norman, OK- Community Rotation 2016