Kidney Stone Institute Team

Andrew John Portis, MD
Chair, HealthEast Kidney Stone Institute

Andrew John Portis, MD is Chair of the HealthEast Kidney Stone Institute. His time is dedicated to the evaluation, treatment and prevention of kidney stones and stone disease. Dr. Portis deeply believes that education and prevention are essential parts of the treatment process. He works closely with patients to help them reduce the chances of developing future kidney stones.

Dr. Portis completed medical school and urology residency training in Edmonton, Alberta, Canada. He then completed a two-year fellowship in minimally invasive urology at the prestigious Barnes-Jewish Hospital, Washington University in St. Louis Medical School.

Since 2000, Dr. Portis has been providing innovative surgical solutions for upper urinary tract disease. He has also developed new strategies for clearing kidney stones, including ureteroscopic laser lithotripsy with active fragment clearance and tubeless percutaneous nephrolithotomy. Both procedures are less invasive than other treatment options and are highly effective.

Dr. Portis pays careful attention to his patients’ outcomes and often conducts research that leads to improvements in patient care. Actively involved in national and international research societies, he shares his findings with other urology specialists.

Passionate about helping others, Dr. Portis has a special interest in treating Hmong Americans with kidney stones. His research has documented a high rate of uric acid stone disease in the Hmong community. He is actively working with the community to understand the causes and develop strategies to treat those with the uric acid stones.

In addition to stone disease, Dr. Portis has extensive experience in laparoscopic surgery where he focuses on benign and malignant conditions of the kidney, ureter and adrenal gland.

Carl Bretzke, MD
Interventional Radiologist

Carl Bretzke, MD is a board-certified radiologist. He has been a member of St. Joseph's medical staff since 1987 and was chairman of the hospital's radiology department from 1995 to 2005.

Over the past 20 years, Dr. Bretzke has performed more than 1,000 percutaneous nephrolithotomy (PCNL) procedures. He continues to perform 50 to 100 PCNL stone removal cases each year.

Born and raised in Hutchinson, Minnesota, Dr. Bretzke earned a bachelor's degree from the University of Colorado, Boulder and then completed medical school and residency training at the University of Minnesota .

Dr. Bretzke trained in interventional radiology with Kurt Amplatz, MD, a pioneer in interventional radiology and endourology.

Caroline Dietz, RN, BSN
Program Director

Caroline Dietz, RN, is the Program Director for the HealthEast Kidney Stone Institute. She is a graduate of the St. Cloud School of Nursing, and completed her bachelor of science at the College of St. Francis, Joliet, Illinois. She is currently enrolled in the Master of Arts in Organizational Leadership program at the College of St. Catherine, St. Paul, Minnesota.

Caroline has more than 35 years of experience in nursing in a variety of settings. In addition to program development, project management and performance improvement, she also has an extensive clinical background. Caroline has a passion for program development and is committed to designing a program centered around the needs of patients with kidney stones.