Dr. Brian S. Lim is a compassionate and highly accomplished clinician, educator, and researcher. He is a nationally distinguished Fellow of the American College of Gastroenterology, American Society of Gastrointestinal Endoscopy, American Gastroenterological Association and the American College of Physician which are designations recognizing members who have demonstrated superior competence and made significant contributions to the field of gastroenterology, endoscopy, and internal medicine. He is an Associate Professor of Medicine for UC Riverside School of Medicine and former core faculty for UC Riverside Internal Medicine and Kaiser Inland Empire Internal Medicine Residency Programs for which he was recognized with numerous accolades.


He graduated with Honors from Chicago Medical School and was inducted into the exclusive Alpha Omega Alpha Medical Honor Society which recognizes the top 15% of the graduating class for their academic achievements and dedication to the profession of medicine.

He completed his internal medicine residency at UCLA-San Fernando Valley Internal Medicine program where he served as Chief Resident.

His gastroenterology fellowship was completed at UC Davis where he acquired training in advanced endoscopy, earned his Master’s in Clinical Research, and received the ACG Governor’s Clinical Research Award.

Dr. Lim has an elite set of endoscopic skills and vast experience with complex endoscopy. Before joining United Gastroenterologists, Dr. Lim practiced at Kaiser Riverside Medical Center for 13 years as an advanced/pancreatobiliary endoscopist performing procedures such as endoscopic ultrasound (EUS), endoscopic retrograde cholangiopancreatography (ERCP), and enteral stenting. Few gastroenterologists have his colonoscopy and polyp removal skill set. His skills encompass endoscopic mucosal resection (EMR) of large and giant polyps to progressive techniques like endoscopic submucosal dissection (ESD) for early cancer, endoscopic full-thickness resection (EFTR) for refractory polyp and early cancer, and endoscopic suturing, all of which are performed largely in academic centers. He is ASGE STAR certified for Upper and Lower Endoscopic Mucosal Resection.

While his main passion is for patient care and helping patients understand their disease processes and management, he has been acknowledged for his numerous accolades as an educator, leader, and researcher. In addition to his academic titles at UC Riverside and Kaiser, he also held positions as an area research chair and residency research co-chair. His numerous awards include Internist of the Year Award, Excellence in Teaching Award, Kaiser Permanente Southern California Physician Researcher of the Year Award, and American College of Physicians Distinguished Teacher/Mentor Award. Dr. Lim has contributed numerous research articles, case reports, educational videos, book chapters and had the privilege of presenting the results of his research at national meetings. He remains an active manuscript reviewer for several peer reviewed medical journals.

He has received the Southern California Super Doctors recognition for four consecutive years and is an active member of the American Gastroenterological Association and Christian Medical & Dental Association.

Dr. Lim is committed to providing up to date evidence-based medicine with empathy. When not working, he likes spending time with his family, attending/serving at church, and pursuing his musical interests, especially singing.

Board Certifications
American Board of Gastroenterology 2009 and 2021
American Board of Internal Medicine 2006


Fellow of American College of Physicians (ACP)
Fellow of American College of Gastroenterology (FACG)
Fellow of the American Society of Gastrointestinal Endoscopy (FASGE)
Fellow of American Gastroenterological Association (AGAF)
Super Doctors Award – Southern California Super Doctors (2020, 2021, 2022, 2023)
American College of Physicians Southern California Region 2 Distinguished Teacher/Mentor Award
2021ASGE STAR certified Upper and Lower Endoscopic Mucosal Resection


Medical Education
The Chicago Medical School/Rosalind Franklin University of Medicine Science (graduated with AOA honors) 2002


UCLA-San Fernando Valley Internal Medicine Program 2005 (Chief Resident 2006)


Fellowship Training
UC Davis, Gastroenterology 2009


Office Locations
Irvine – T:  (949) 502-5572 | 16405 Sand Canyon Ave Ste. 250, Irvine, CA 92618
Mission Viejo | T: (949) 364-2611, 26732 Crown Valley Pkwy #241, Mission Viejo, CA 92691

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