Our Team

Meet Our Providers

Ernest F. Ribera, MD

Dr. Ribera is a board-certified gastroenterologist with more than 25 years of experience. His fellowship in Gastroenterology included training at the Naval Medical Center, San Diego, UCSD, and UCSF. He also served as an Adjunct Associate Professor at Stanford University Medical School for over ten years. Dr. Ribera graduated from the University of Notre Dame and participated in track and cross country. He attended medical school at the College of Human Medicine of Michigan State University. While there, he was awarded the Armed Forces Health Professions scholarship. Dr. Ribera is currently on the professional staff at Mills-Peninsula Hospitals and has previously served as Chair of the Department of Internal Medicine. He has served as the gastroenterologist for the Samaritan House Clinic since its inception and also supports Operation Access patients. Dr. Ribera is the past president of the Northern California Society for Clinical Gastroenterology. He is also a retired Captain in the Medical Corps of the United States Navy. Most of the upper endoscopy and colonoscopy procedures performed by Dr. Ribera are done at the Mid-Peninsula Endoscopy Center, which is located on the same floor as his office in Burlingame. This endoscopy center is recognized for quality and safety by the American Society for Gastrointestinal Endoscopy. MPEC is the first endoscopy center in the Bay Area to provide the Medtronic AI technology for colonoscopy.Dr. Ribera and his wife Maria are the proud parents of four children and three grandchildren.

Sara Sameshima, PA-C

Sara Sameshima is a board-certified Physician Assistant (PA) with experience in Emergency Medicine and now Gastroenterology. Born and raised in Honolulu, Hawaii, Sara left the islands for the University of Southern California(USC) in Los Angeles. After graduating as a cum laude Renaissance Scholar from USC in 2012, Sara taught English in southern Japan for a year before returning to the states to pursue her career in medicine. She also has experience working in clinical research with the University of Hawaii Cancer Center studying the relationships between ethnicity, body fat distribution, diet, and cancer risk as well as with allergy & asthma clinical trials. She graduated from the Keck School of Medicine of USC's PA Program in 2018 after being inducted into the prestigious Pi Alpha Honor Society and joined Dr. Ribera's practice in July 2018. Sara is passionate about preventative health practices in gastrointestinal health and approaching the patient as a whole to determine the best course of treatment. In her spare time, Sara enjoys traveling, trying new foods, watching USC Trojan football, and exploring the Bay Area with her husband and daughter.