At General Surgery Associates LLC, Our Providers Specialize in a Diverse Variety of Medical Procedures & Services

We offer a wide range of services, from general surgery to highly specialized medical procedures. Listed below are a few of our practice areas:

Abdomen
Colorectal
Endocrine Surgery
Breast Surgery
Esophageal
Stomach/Gastric
Gallbladder
Appendix
Hernia Surgery
Skin & Soft Tissue
Emergency Surgery
Robotic Surgery

About Us

Stephen Nagengast, MD

A Nebraska native, Dr. Stephen Nagengast graduated from Bloomfield High School. He went on to attend Creighton University where he excelled and received his Medical Degree from the Creighton University School of Medicine. He completed his Surgical Internship and Residency at Phoenix Integrated Surgical Residency Program, serving as Chief Resident in General Surgery. Dr. Nagengast is Board Certified by the American Board of Surgery.

Dr. Nagengast began practicing in Lincoln in 1991. He practices all aspects of general and advanced laparoscopic surgery. He has been recognized as an Active Teacher in Family Medicine by the American Academy of Family Physicians. He is a member of the Lancaster County Medical Society, Nebraska Medical Association, and the American Medical Association. Dr. Nagengast received the Outstanding Rural Health Practitioner Award in 2012. This award recognizes providers who exhibit outstanding leadership, dedicated care, and collaboration in improving health services in Rural Nebraska. Dr. Nagengast credits his father for his strong work ethic. His father was a small town family doctor in his hometown of Bloomfield for more than 50 years. His father’s service and love of his profession had a strong influence on the man Dr. Nagengast is today. In the early 1990’s he began serving the rural communities of Auburn, Crete, Nebraska City, Osceola, and Syracuse and his office has been serving these communities ever since. Dr. Nagengast enjoys spending time with his wife and six children. He is an avid outdoorsman who spends time each year fishing and hunting.

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John Fallick, MD

Dr. John Fallick is a native of Columbus, NE where he graduated from Columbus High School. He is a graduate of High Distinction in Biology from Nebraska Wesleyan University. Dr. Fallick received his Medical Degree from University of Nebraska Medical Center again graduating with Distinction. He completed his Residency in General Surgery at Mayo Graduate School of Medicine. Dr. Fallick is Board Certified by the American Board of Surgery.

Dr. Fallick began practicing in Lincoln when he joined Dr. Stephen Nagengast at General Surgery Associates in 1999. He practices all aspects of general and advanced laparoscopic and robotic-assisted surgery. He has been recognized as an Active Teacher in Family Medicine by the American Academy of Family Physicians. He has also been very involved in medical staff development at Bryan Health, completing a two-year term as Department of Surgery Chair. He is a member of the Lancaster County Medical Society, Nebraska Medical Association, and the American Medical Association. Dr. Fallick enjoys spending time with his wife and four daughters. When not at home, they can be found at the lake or at a sporting event. They enjoy all things BIG RED!

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Brad Olberding, MD, FACS

Dr. Brad Olberding, better known as Dr. O, is a native of Stuart, NE. He did his undergraduate studies at UNL before attending the University of Nebraska Medical Center where he graduated with Distinction.

He completed his General Surgery Residency at Banner University Medical Center in Phoenix, AZ where he was awarded the Administrative Chief position. Dr. Olberding is Board Certified by the American Board of Surgery and is a Junior Fellow of the American College of Surgeons.

Dr. Olberding is a Veteran of the Army National Guard and served three Tours of Duty, getting his start in medicine as a flight medic and EMT. Dr. Olberding began practicing with General Surgery Associates in 2014. In addition to his Lincoln clinic, he serves the communities of Syracuse, Nebraska City, and Fairbury. He practices all aspects of general and advanced laparoscopic and robotic-assisted surgery. He is a member of the Nebraska Medical Association, Lancaster County Medical Society, and American Medical Association. Brad enjoys spending time with his wife Jackie and their son Arlo. He enjoys everything sports, especially when it comes to the Huskers! GO BIG RED!

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Clint Rathje, DO

Dr. Rathje grew up on a farm just outside of Aurora, Nebraska and received his Bachelor of Science degree from the University of Nebraska-Lincoln. He went on to earn his medical degree from Kansas City University of Medicine and Biosciences where he graduated with honors. He also obtained his Masters of Business Administration in Healthcare Leadership from Rockhurst University in Kansas City while attending medical school. He completed his General Surgery Residency at the University of Kansas in Wichita, Kansas. Dr. Rathje is Board Certified by the American Board of Surgery.

Dr. Rathje enjoys all aspects of general surgery including advanced laparoscopic and robotic-assisted surgery. He is a member of the Nebraska Medical Association, Lancaster County Medical Society, and American Medical Association. In his free time he enjoys spending time with his wife, Mandi and their four daughters. He enjoys being outdoors, DIY projects, and watching college football, GO HUSKERS!

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Heather Liss, PA-C

Heather is a Nebraska native, growing up in Seward. She received her Bachelor of Science degree from Doane College in 2004 and her Master of Physician Assistant Studies from the University of Nebraska Medical Center in Omaha in 2006. Heather is board certified by the National Commission on Certification of Physician Assistants.

She has worked in general surgery her entire career and takes pride in the personal relationships built with patients of all ages.

Heather lives in Lincoln with her husband and two children. She enjoys running, traveling, and spending time with family and friends. As a Physician Assistant at General Surgery Associates, Heather assists in direct patient care in the office, hospital and surgery.

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Jessica Zaruba, PA-C

Jessica grew up in Norfolk, NE and received her Bachelor of Science degree from College of Saint Mary in Omaha, NE. She graduated from Union College in 2017 with her Master of Physician Assistant Studies. Jessica is board certified by the National Commission on Certification of Physician Assistants.

Jessica is looking forward to an exciting career in general surgery. Throughout her clinical rotations she was exposed to every facet of medicine and found general surgery to be her passion.

She is looking forward to building relationships with patients in our office and helping them to successfully regain their way of life after surgery. Jessica lives in Lincoln and in her spare time she enjoys physical fitness, outdoor activities, reading, and spending time with her family and friends. As a Physician Assistant with General Surgery Associates, Jessica assists in direct patient care in the office, hospital, and surgery.

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Alli Koester, PA-C

Alli is a Nebraska girl, who grew up in Kearney. She received her Bachelor of Radiographic Sciences from the University of Nebraska Medical Center, where she graduated with highest distinction. She attended the Physician Assistant program at Wichita State University and graduated in 2016 with her Master of Physician Assistant. Alli is board certified by the National Commission on Certification of Physician Assistants.

She started her career in vascular surgery at the Nebraska Heart Hospital. Alli is excited to continue her career in general surgery for the variety of procedures and patients.

Alli lives in Lincoln with her husband. She enjoys yoga, group fitness, reading, and tending to her plants. As a Physician Assistant with General Surgery Associates, Alli assists in direct patient care in the office, hospital, and surgery.