Doctors

Mark W. Wells

Dr. Mark Wells joined Gastroenterology Specialties, PC in 2017 after two years of practice in Montana. Originally from Beebe, Arkansas, Dr. Wells graduated medical school from the University of Arkansas for Medical Sciences, where he also completed his Residency in Internal Medicine in 2010.

After being selected to serve as Chief Resident in Internal Medicine in 2011, Dr. Wells worked a year as a senior medical officer in New Zealand prior to beginning his Gastroenterology Fellowship at the University of Nebraska Medical Center. Dr. Wells completed his Gastroenterology Fellowship in 2015.  He is Board Certified in Gastroenterology and Internal Medicine by the American Board of Medicine.

Laura M. Vance

Dr. Laura Vance graduated medical school from Des Moines University in 2016.  Originally from Iowa she fell in love with Nebraska after completing her Internal Medicine residency at University of Nebraska Medical Center (UNMC) and Gastroenterology fellowship at Creighton University School of Medicine.  She worked as a Hospitalist at UNMC from 2019-2020.  She is board certified in Internal Medicine and Gastroenterology.  Dr. Vance has a passion for her career.  When away from the office, she enjoys spending quality time with her family and friends, living an active lifestyle, and traveling.

J. Reggie Thomas

Dr. J. Reggie Thomas is a graduate of the Kirksville College of Osteopathic Medicine in Kirksville, Missouri (2007).  He completed his Internal Medicine Residency and his Gastroenterology Fellowship at Banner Good Samaritan Medical Center in Phoenix, Arizona.  Dr. Thomas is board certified in both Internal Medicine and Gastroenterology by the American Board of Internal Medicine.

Michael P. Roth

Dr. Michael Roth is a graduate of the University of Nebraska College of Medicine in Omaha (2004).
He completed both his Internal Medicine Residency, Gastroenterology fellowship, and advanced endoscopic training at the McGaw Medical Center of Northwestern Memorial Hospital in Chicago.

Dr. Roth is Board Certified in both Internal Medicine and Gastroenterology.  He has an interest in celiac disease and extra training in advanced endoscopic procedures such as ERCP, EUS, and RFA.

James W. Roat

Dr. Roat graduated from the University of Pennsylvania with a degree in chemistry. He attended medical school at the University of Nebraska Medical Center. He completed Internal Medicine residency at the University of Minnesota and a fellowship in Gastroenterology at the University of Cincinnati. He also completed an advanced endoscopy fellowship at the University of Cincinnati. Dr. Roat is Board Certified in both Internal Medicine and Gastroenterology by the American Board of Internal Medicine.

Christopher C. Rife

Dr. Christopher C. Rife is a graduate of the University of Nebraska College of Medicine in Omaha (2008). He completed his Internal Medicine Residency at the Medical University of South Carolina in 2011.  Dr. Rife also completed his Gastroenterology Fellowship at the Medical University of South Carolina in July 2015. Dr. Rife is Board Certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine.

Paul F. Petersen

Dr. Paul F. Petersen has been in practice since 1997. Dr. Petersen is a graduate of the University of Nebraska College of Medicine in Omaha. He completed his Residency at St. Louis University Hospital. Dr. Petersen completed his Fellowship at St. Louis University Hospital where he was Chief Fellow. Dr. Petersen is Board Certified in Gastroenterology by the America Board of Internal Medicine.

David P. Newton

Dr. Newton joined Gastroenterology Specialties, PC in 2017.  Dr. Newton graduated in 2009 from the University of Nebraska Medical Center College of Medicine, Omaha.  He completed an internship and residency in Internal Medicine at the University of Alabama at Birmingham School of Medicine, then returned to the University of Nebraska Medical Center to complete a fellowship in gastroenterology and hepatology. He has presented at several national conferences.

Before joining Gastroenterology Specialties, PC, Dr. Newton was with the Iowa Digestive Disease Center and Iowa Endoscopy Center in Clive, Iowa. He is board certified in Gastroenterology and Internal Medicine by the American Board of Medicine.

William J. Lawton

Dr. William J. Lawton is a graduate of the University of Nebraska College of Medicine in Omaha (2005). He completed his Internal Medicine Residency at the University of Nebraska Medical Center in 2008, and served as Chief Resident in Internal Medicine until 2009. Dr. Lawton also completed his Gastroenterology fellowship at the University of Nebraska in July 2012.

He is Board Certified in both Internal Medicine and Gastroenterology by the American Board of Internal Medicine.

Sally A.I. Knooihuizen

Dr. Sally Knooihuizen was born and raised in Lincoln and received her Bachelor of Chemical Engineering from Vanderbilt University. She then graduated from the University of Nebraska College of Medicine in 2017. She completed her Internal Medicine residency at Massachusetts General Hospital and her Gastroenterology fellowship at the University of Texas Southwestern in Dallas, Texas. She has a special interest in liver disease and was an AASLD Emerging Liver Scholar in residency.  She is board certified in Internal Medicine and Gastroenterology.  When not in the office, Dr. Knooihuizen enjoys spending time with her family, outdoor activities, reading, and baking.

Matthew J. Hrnicek

Dr. Matthew J. Hrnicek has been in practice since 2005.  He is a graduate of the University of Nebraska College of Medicine in Omaha.  He completed his Internship, Residency and Fellowship at the University of Nebraska College of Medicine.  Dr Hrnicek is Board Certified in Gastroenterology by the America Board of Internal Medicine.

Mark G. Griffin

Dr. Mark G. Griffin has been in practice since 1990. Dr. Griffin is a graduate of the University of Missouri-Kansas City School of Medicine. He completed his Residency at the University of Colorado Health Sciences where he served as a Clinical Instructor, Staff Physician Specialist, and Medical Director at a walk-in Clinic in Denver General Hospital.

Dr. Griffin completed his Fellowship at the University of Kansas Medical Center. Dr. Griffin is Board Certified in Gastroenterology by the America Board of Internal Medicine.

Erik A. Bowman

Dr. Bowman graduated from Nebraska Wesleyan University in 2005 with a degree in biochemistry/Molecular Biology. He attended medical school at the University of Nebraska Medical Center in Omaha.  He completed his Internal Medicine residency, Gastroenterology/Hepatology fellowship and advanced endoscopy fellowship at the University of Wisconsin in Madison.

Dr. Bowman is board certified in Internal Medicine and Gastroenterology through the American Board of Internal Medicine.  He has special interest in ERCP, EUS, RFA and EMR procedures.

Clark W. Antonson

Dr. Clark Antonson has been in practice since 1985. Dr. Antonson is a graduate of the University of Nebraska College of Medicine in Omaha. He completed his Residency at the University of Nebraska College of Medicine and his Fellowship at Kansas University Medical Center.

He served as Assistant Professor at the University of Kansas Hospital and Kansas City Veteran’s Hospital.   Dr. Antonson is Board Certified in Gastroenterology by the American Board of Internal Medicine.

Dr. Antonson is a fellow in the ACG and past president of the Nebraska Gut Club. He is presently Governor of the ACG for the state of Nebraska.