Our Providers

Erik Van Os MD

Erik Van Os

William W. Lunt MD

William W. Lunt

Austin E. Garza MD

Austin E. Garza

Karin Cesario MD

Karin Cesario

Bryan C. Kavanaugh MD

Bryan C. Kavanaugh

Michael J. Baker MD

Michael J. Baker

C. Scott Swendsen, MD

C. Scott Swendsen,

C. Noelle O’Shea, DO

C. Noelle O’Shea,

Matthew Drew, MD

Matthew Drew,

Diana Arsene, MD

Diana Arsene, MD

PA-C Michelle Barnett

Michelle Barnett
Physician Assistant

NP Sarah Garza

Sarah Garza
Nurse Practitioner

PA-C Courtney Frerichs

Courtney Frerichs
Physician Assistant

PA-C Gayleen Prausa

Gayleen Prausa
Physician Assistant

NP Julie Cotton

Julie Cotton
Nurse Practitioner

Erik Van Os, MD

Michael J. Baker, MD

Dr. Baker joined Associates in Gastroenterology August of 2011. A native of the West, he grew up in Billings, MT. and completed his undergraduate education at the University of Montana (Go Griz!). Dr. Baker earned his M.D. from the University of Washington in 2005. He completed his Internal Medicine training at the University of Colorado Health Sciences Center in Denver, C.O. in 2008 and then completed his gastroenterology fellowship at The Ohio State University Medical Center in 2011.

Dr. Baker’s clinical interests include all facets of the practice of gastroenterology and hepatology. He also has a special interest in the diagnosis and management of inflammatory bowel disease (crohn’s disease and ulcerative colitis) as well as therapeutic pancreatico-biliary endoscopy (ERCP).

His personal interests include golfing, fly fishing, skiing and getting back up to Montana for some hiking in the Beartooth Mountains. He also enjoys spending time with his family and dogs.

Gayleen Prausa, PA-C Physician Assistant

Gayleen Prausa, PA-C joined Associates in Gastroenterology in 2017. A Montana native, she earned her Bachelor of Arts degree in Biology from Carroll College in Helena, MT in 1998. After 4 years as a Respiratory Therapist working in emergency care, telemetry, and intensive care units on the east coast, she completed her master’s degree from Massachusetts College of Pharmacy & Health Sciences in Manchester, NH. After moving to beautiful Colorado, she worked in internal medicine and family practice for 11 years prior to transitioning to gastroenterology. Gayleen is a nationally certified Physician Assistant thru the NCCPA and is a member of the American Academy of Physician Assistants.

She enjoys spending time with her husband and 2 children, reading, hiking, biking and traveling.

C. Noelle O’Shea, DO

Dr. O’Shea received her undergraduate education in Math and Chemistry at William Woods University. She received her graduate education at the University of West Florida and Troy State University. She received her medical degree from Western University of Health Sciences in Pomona, CA. She then completed her internal medicine residency at the University of Texas Medical Branch in Galveston, TX followed by a gastroenterology fellowship at the University of Texas in Houston, TX.

She is a member of the ACG and ASGE.

Personal interests include hiking.

Austin Garza, MD

Dr. Garza received both his undergraduate and medical education at Vanderbilt University in Nashville, Tennessee. He chose to remain at Vanderbilt for his Internal Medicine residency, and completed a fellowship in Gastroenterology and Hepatology at the University of South Florida and H. Lee Moffitt Cancer Center in Tampa, Florida. He is board certified in both Internal Medicine, and Gastroenterology and Hepatology. He has been with Associates in Gastroenterology since 2006.

Dr. Garza has authored multiple peer-reviewed publications in the fields of inflammatory bowel disease, gastrointestinal malignancies, swallowing disorders, and esophageal disease. He is a member of the ACG, AGA, and ASGE. Clinical interests include gastrointestinal oncology, esophageal disease and IBD.

Dr. Garza performs all endoscopic procedures, including colonoscopy, EGD, ERCP and EUS. He has performed over 1000 EUS procedures at Penrose Hospital to diagnose and stage gastrointestinal malignancy, as well to palliate pain from pancreatic cancer.

Dr. Garza currently serves on the Credentialing Committee for the Penrose-St. Francis Health System. He is the current president of our practice, and also is active with GI practice management on the national level, representing the practice by serving with the Digestive Health Physicians Association.

Personal interests include skiing, hiking 14ers (his favorite is Capitol Peak), cooking, and playing piano. He and his wife Sarah have three children, and two dogs including a yellow lab named Pearl who enjoys carbs and all things gluten.

Dr. Garza is one of many A.G. physicians who has been recognized as one of Colorado Springs’ “Top Docs” in gastroenterology.

Bryan Kavanaugh, MD

Dr Kavanaugh joined the practice August 2010. He is board certified in Gastroenterology and Hepatology and has training in the endoscopic management of pancreatic and biliary disorders in addition to standard diagnostic and therapeutic endoscopic procedures. His clinical interests include the management of inflammatory bowel diseases, Celiac, and irritable bowel syndrome.

Dr Kavanaugh received his undergraduate and Master’s degrees in biology from Rutgers University in New Jersey. He then attended medical school at Georgetown University in Washington, DC. He completed his internal medicine internship, residency, and fellowship at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania. While he was an intern, he was honored with the “Intern of the Year” award, nominated by peers and faculty for outstanding performance during internship. Dr Kavanaugh also was the Chief Medical Resident at Thomas Jefferson University Hospital, to supervising the training of medical residents and students.

He has four boys and his hobbies are keeping them out of trouble.

William W. Lunt, MD

Dr. Lunt is certified by the American Board of Internal Medicine in gastroenterology. He is an active member of the AMA, AGA, ACG, and the ASGE. He is fully trained in all endoscopic procedures, and specializes in endoscopic ultrasound. He practices in all aspects of gastroenterology but has special interests in liver disease and GI malignancies.

Dr. Lunt graduated from the University of Wyoming in 1985 with a Bachelor in Science. After 3 years as a carpenter, emergency room tech, mountain guide and river guide, Dr. Lunt enrolled at Creighton University School of Medicine in Omaha, Nebraska, graduating in 1992. After medical school from 1992-1996 he attended the University of Wisconsin where he completed one year of radiology training followed by a three-year residency in Internal Medicine. He then attended the University of Arizona Medical Center for 3 years of advanced training in gastroenterology and hepatology. Since 1999, Dr. Lunt has been in practice with Associates of Gastroenterology in Colorado Springs.

In addition to general gastroenterology, Dr. Lunt has special clinical interests in liver and pancreatic disease. He is fully trained in all aspects of therapeutic intestinal and biliary endoscopy. Dr. Lunt also has advanced training in endoscopic ultrasound (EUS). This technique uses intraluminal ultrasound to diagnose and manage many intestinal malignancies. He also has received special training in bowel and anal functions and is fully certified to evaluate for Interstim Sacral Nerve modulation to assist those patients with bowel incontinence.

Michelle Barnett, PA-C Physician Assistant

Michelle Barnett has been with Associates in Gastroenterology since 2001. In 1983, she completed her undergraduate degree in chemistry at Kansas Newman College in Wichita, Kansas. She graduated from the PA program at Wichita State University in 1986 and completed her Master’s degree at the University of Nebraska in 1998. She is a member of AASLD and ACG and has been a board member of the Colorado Academy of Physician Assistants for many years. Clinical interests include viral hepatitis, complications of liver disease, chronic constipation and inflammatory bowel disorders.

She enjoys travel, reading and spending time with her husband and 3 children.

Courtney Frerichs, PA-C Physician Assistant

Courtney Frerichs, PA-C joined Associates in Gastroenterology in 2012. An Arizona native, she graduated from the University of Arizona in 2005 with a Bachelor of Science Degree in Physiology. After moving to beautiful Colorado, she graduated from the Red Rocks Community College Physician Assistant Program, and also completed a Masters Degree in Medical Science from Saint Francis University in 2012. Courtney is nationally certified by the National Commission on Certification of Physician Assistants (NCCPA). She is a member of the American Academy of Physician Assistants, Colorado Academy of the Physician Assistants, and the American College of Gastroenterology.

Her personal interests are spending time being active and exploring beautiful Colorado by running, mountain biking, snowboarding, and hiking with her husband, children and dogs.

Sarah Garza, NP Nurse Practitioner

Sarah Garza, NP joined Associates in Gastroenterology in 2008. Sarah earned her undergraduate degree at Vanderbilt University in 1997, and she completed her MSN in 1998 at Vanderbilt as well. She brings years of expertise and experience in the field of gastroenterology to our practice, having previously worked in private practice in Nashville, Tennessee, and then at the prestigous Joy McCann Culverhouse Center for Swallowing Disorders in Tampa, Florida. At the Center for Swallowing Disorders she worked under international experts focussing on esophageal disease. She has extensive experience and expertise in esophageal dysmotility, achalasia, esophageal strictures, as well as other conditions affecting the esophagus. She also has the knowledge from many years of general GI and hepatology practice to offer our patients at Associates in Gastroenterology.

She enjoys spending time with her husband, Austin, and their 3 children. Personal interests include traveling, cooking, and tennis.

Erik Van Os, MD

Dr. Van Os graduated from Rice University in Houston, Texas and then attended the University of Texas Southwestern Medical School in Dallas. Following this he completed internship and residency in internal medicine at the University of Texas Health Science Center in San Antonio. After serving on the faculty of the medical center in San Antonio for 2 ½ years, Dr. Van Os completed fellowships in gastroenterology and advanced therapeutic endoscopy at the Mayo Clinic in Rochester, Minnesota.

Dr. Van Os joined Associates in Gastroenterology in 1996. His interest is general gastroenterology. He currently serves on the Medical Executive Committee and the Board of Trustees for the Penrose-St. Francis Health System. In addition, Dr. Van Os serves on the Regional Coordinating Council and Finance Committees for Colorado Health Neighborhoods.

Julie Cotton, NP-C Nurse Practitioner

Julie Cotton, NP-C graduated from Arizona State University in 2009 with a Bachelor of Science Degree in Nursing. She received her Master’s Degree in Science of Nursing from Grand Canyon University. She is board certified by the American Nurses Credentialing Center as an Adult-Gerontology Acute Care Nurse Practitioner. She joins the team at Associates in Gastroenterology to provide quality, compassionate, and holistic care to our gastroenterology and hepatology patients.

She is a member of the American Academy of Nurse Practitioners. Prior to pursuing her advanced practice degree, Julie worked as a Registered Nurse in a variety of hospital settings including medical-surgical unit, telemetry, interventional radiology, and intensive care unit. She brings over experience in the field of gastroenterology to our patients.

In her personal time, Julie enjoys spending time with her husband. Her hobbies include hiking, camping, cooking, reading, and traveling. She is involved in the PSC spouses club to volunteer and support our troops.

Karin Cesario, MD

Dr. Cesario completed her undergraduate studies at Washington University in St. Louis and then returned to her native Denver to attend medical school at the University of Colorado. She stayed on at the University of Colorado to complete her internal medicine residency and graduated in 2003. Dr. Cesario then moved to Ohio to complete her gastroenterology fellowship at the Cleveland Clinic. After receiving a prestigious 2006 American Association for the Study of Liver Diseases (AASLD) advanced fellowship, she spent an additional year at the Cleveland Clinic studying clinical hepatology and liver transplantation. She was board certified by the American Board of Internal Medicine in gastroenterology in 2006 and received her transplant hepatology certification in 2008. She has been thrilled to practice with Associates in Gastroenterology since 2008 and remains the only board-certified transplant hepatologist in all of southern Colorado.

Dr. Cesario has received several research grants and authored multiple publications, predominantly in the area of hepatitis C. She has consistently been listed as one the “Top Docs” in Colorado Springs as voted on by her peers and published annually in the Colorado Springs Style magazine. She is an active member of the AASLD, the American College of Gastroenterology (ACG) and is serving her second term on the Medical Advisory Committee of the American Liver Foundation (ALF), Rocky Mountain Division. Her clinical interests include viral hepatitis and complications of liver cirrhosis. Her personal interests include traveling, Orange Theory Fitness and spending time with her husband and their four children.

C. Scott Swendsen, MD

Dr. Swendsen received his undergraduate education in Biology and Business at Brigham Young University. He received his medical degree from the University of Utah in Salt Lake City, UT in 2010. He then completed his internal medicine residency and gastroenterology fellowship at Baylor Scott & White – Texas A&M University in Temple, TX. In addition to his training in general gastroenterology and hepatology, he went on to get additional training in advanced endoscopy for pancreas and biliary procedures including ERCP and EUS (endoscopic ultrasound). He received his board certification in Gastroenterology and Hepatology in 2016.

His clinical interests include pancreas and biliary disorders, inflammatory bowel disease, Hepatitis C and cirrhosis, and reflux disease. Dr. Swendsen has been involved in research centered on patient safety and quality improvement. He is a member of the ACG, AGA, and ASGE.

Personal interests include spending time with his wife and four children, skiing, camping, and playing sports.

Matthew Drew, MD

Dr. Drew is excited to join Associates in Gastroenterology. Originally from England, Dr. Drew has spent most of his life on the east coast. He went to Robert Wood Johnson Medical School. For residency, he trained at Yale-New Haven Hospital in New Haven, CT. He completed his gastroenterology training at Cooper University Hospital in Camden, NJ. In addition to General GI, Dr. Drew is trained in esophageal motility and video capsule endoscopy. He is active in the American College Gastroenterology as a member of the Training Committee.

Dr. Drew welcomes new patients to his practice. He is eager to help, listen to his patient’s problems, and formulate a plan with his patient’s input. In his spare time, he enjoys music, exercise, and the outdoors.

Diana Arsene, MD

Dr. Arsene is excited to join Associates in Gastroenterology. She grew up outside of Toronto, Canada, and completed her undergraduate education in Biochemistry at the University of Waterloo, in Canada, prior to migrating south, and receiving her medical degree at the University of Miami, in Miami, FL. She completed residency in Internal Medicine at the Los Angeles County-University of Southern California Medical Center, in Los Angeles, CA. She went on to complete her gastroenterology fellowship program in a combined research-clinical track at the University of North Carolina in Chapel Hill, NC, with focus on the role of the microbiota in Crohn’s Disease and Ulcerative Colitis.
Her clinical interests include inflammatory bowel diseases, but also anorectal disorders, irritable bowel syndrome, and disorders of the liver, with focus on patient communication and education.
Her personal interests include cycling, hiking, camping, and spending time with her husband and two young daughters.