Our Providers

Meet Our Team

Dr. David Warren Monahan, FACP

Dr David Warren Monahan MD FACPDr. Monahan has been named a Top Doctor multiple times by Northern Virginia Magazine. Currently he is the managing partner of Fall Hill Gastroenterology Associates in Fredericksburg, Virginia, where he has practiced since 1993.
Dr. Monahan earned his medical degree at the Bowman Gray School of Medicine at Wake Forest University in 1981, after graduating from Cornell University.
He completed his Internal Medicine residency while on active duty at Letterman Army Medical Center, San Francisco, CA in 1984. He then served as a general internist in the US Army stationed in Germany, and received the prestigious Robert Moser Award for the Top Internist in the US Army.
Dr. Monahan has been a Gastroenterologist since he completed his Fellowship at Brooke Army Medical Center, San Antonio, TX, in 1990. Next he served as chief of Gastroenterology at Womack Army Medical Center at Fort Bragg, NC. Since 1993 he has been with Fall Hill Gastroenterology Associates.
He is board certified in Gastroenterology since 1991 and a Fellow in the American College of Physicians since 1998. He has served as Endoscopy Committee Chief at Mary Washington Hospital.
Dr. Monahan lives with his wife in Spotsylvania and enjoys waterskiing and computer gadgets. As a military dependent growing up he lived in many places, but he calls Virginia home.
His special medical interests include general gastrointestinal and liver diseases, colon cancer screening, video capsule endoscopy and biliary endoscopy (ERCP).

Dr. Thomas A. Mastri

Dr Thomas Mastri MDHe has been named as a Top Doctor in Northern Virginia Magazine.Currently he is the Medical Director of Fall Hill Gastroenterology Endoscopy Center and a partner in Fall Hill Gastroenterology Associates.He is a graduate of Robert Wood Johnson Medical School, NJ, in 1985. He completed his Internal Medicine residency at the Medical College of Pennsylvania in 1989.He later served as Chief Resident of Internal Medicine at Episcopal Hospital, Philadelphia. His Gastroenterology fellowship was completed at the Boston Veterans Administration Medical Center in 1991.He became Board Certified in Gastroenterology by the American Board of Internal Medicine in 1991.
He spent nine years working for the Geisinger Medical Group in Pennsylvania prior to joining Fall Hill Gastroenterology Associates in 2000.
Dr. Mastri resides with his wife and family in Spotsylvania. He is active in the public school system and has coached young soccer. He is an avid photographer.
His special medical interests include gastrointestinal and liver diseases, diagnostic and therapeutic endoscopy, video capsule endoscopy and colon cancer screening.

Dr. Lawrence W. Comerford, MD, MS,AGAF

Dr David Warren Monahan MD FACPDr. Comerford joins Fall Hill Gastroenterology Associates in 2019 after 16 years as a practicing Gastroenterologist, most recently at Augusta Health in Fishersville, Virginia.
He is a graduate of the U.S. Naval Academy in Annapolis Maryland in 1983 and spent 10 years in the US Navy as an engineering duty officer working on nuclear submarines and in shipyards. He graduated with a Masters of Science in Mechanical Engineering from the Naval Postgraduate School, Monterey, CA.
He earned his medical degree at the Medical University of South Carolina (MUSC), Charleston SC in 1997.
He completed his Internal Medicine Residency at Mayo Clinic, Rochester MN in 2000. He was awarded the Mayo Department of Medicine’s “Attitude, Commitment, & Excellence Award” in 2000.
In 2003, he completed his Gastroenterology Fellowship at the University of Virginia, Charlottesville, VA . He also participated as a NIH Clinical Research Training Fellow in Digestive Diseases while at UVA. He won the American College of Gastroenterology Fellow Clinical Research Award in 2003. He received his Masters of Science in Health Evaluation Sciences at UVA in 2004.
Dr. Comerford served on the gastroenterology faculty of both the University of Virginia (2003-2005), MUSC (2006-2013), and Edward Via College of Osteopathic Medicine, Blacksburg, VA, 2017-2019 where he has taught medical students, residents, and GI fellows. He received the MUSC Department of Medicine Excellence in Teaching Award in 2008. He served as Head of the Inflammatory Bowel Disease (IBD)Section at MUSC and was active in clinical research in IBD publishing papers and book chapters. He has presented abstracts and been an invited speaker at National medical conferences.
He became Board Certified in Gastroenterology by the American Board of Internal Medicine in 2004. He is a Fellow in the American Gastroenterological Association.
He was a recipient of a Our Health Charlottesville and Shenandoah Valley Magazine’s 2018 Best Bedside Manner Award .
He has 4 grown children and lives in Hanover Virginia. He has been an adult leader in the Boy Scouts of America. His current recreational activities include sailing, fishing, hiking, and travelling.
His medical interests include general gastrointestinal and liver diseases, inflammatory bowel disease, general endoscopy including colon cancer screening, and video capsule endoscopy.

Dr. Barbara J. Arcarese - Clinical Pathologist

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Dr. Barbara J. Arcarese is a graduate of the New York College of Osteopathic Medicine, Old Westbury, NY. She completed her residency in anatomical and clinical pathology at St. Luke’s- Roosevelt Hospital in New York, NY in 2007. In 2009 she completed her fellowship in Surgical Pathology at the Yale University School of Medicine, Bridgeport hospital, Bridgeport, CT. From 2009 to 2011 she worked as the Blood Bank Director and a clinical/anatomical pathologist with Central Connecticut Pathology Consultants in New Britain, Ct.

Dr. Arcarese resides in Richmond, VA with her husband, a cardiologist, and 2 children.

Sanita Piya - Family Nurse Practitioner


Sanita is a Board Certified family nurse practitioner. She graduated from Chamberlain College of Nursing, Chicago, IL in 2016. She received her Bachelor in Science of Nursing from B.P. Koirala Institute of Health Sciences, Nepal in 2003.

She has dedicated more than 10 years of her life in caring patients with utmost creativity, best knowledge, skills and experiences to address patient’s issues and problems to deliver most efficient care. She is a member of American Association of Nurse Practitioners and Society of Gastroenterology Nurses and Associates, Inc.

She resides with her husband, a Pediatric Cardiologist and 2 children in Stafford, VA. She enjoys cooking, decorating and spending quality time with her family.

Michele Lyn Lattimer- Family Nurse Practitioner

Michele is an AANP Certified Family Nurse Practitioner. She was the first in her family to graduate with a College Degree. She graduated with her RN from Sentara School of Health Sciences in Chesapeake, VA in 2007, her BSN from East Carolina University School of Health Sciences in Greenville, NC in 2011, and her MSN in Family Nurse Practitioner from Walden University in Minneapolis, MN in 2016. She is dedicated and compassionate about patient care and has been in the health care field for over eleven years. She is a member of the American Association of Nurse Practitioners, the Society of Gastroenterology Nurses and Associates, Inc., and the Virginia Council of Nurse Practitioners.

She currently resides with her husband, cat and dog in Fredericksburg, VA. She has two step-children and two grand-daughters living in Gates County, NC. Her interests include cooking, nutrition, and physical fitness.

Leslie Cooper- Family Nurse Practitioner


Leslie is a Board Certified family nurse practitioner. She graduated from Indiana State University FNP program in 2017 and received a Masters in Science of Nursing. Prior to becoming a nurse, she worked as a Correctional Deputy for Riverside County Sheriff's Department in Southern California for 6.5 years. She started her nursing career after completing an LPN certificate program through North West College in 2006. Later she went on to completed an LPN to BSN bridge program and received a Bachelor in Science of Nursing in 2011. She has over 13 years of nursing experience in general medicine and various subspecialties such as oncology, cardiology, renal-respiratory.

She resides with her husband and two children in Fredericksburg, VA. Her interests include travel, and outdoor activities with the family to include kayaking, stand up paddle boarding, water skiing, and snow skiing.