Rita E. Thieme, MD, FAAP

Dr. Thieme is a Board Certified Pediatrician who has been with Castle Rock Pediatrics for 16 years. She received her MD in 1989 from the University of Colorado, followed by her residency in Pediatrics at The Children’s Hospital in Denver. Dr. Thieme also had two years of specialty training in Pediatric Nephrology (Kidney Disease).

Following her fellowship, Dr. Thieme worked as a Pediatric Emergency Physician at Swedish Medical Center prior to joining Castle Rock Pediatrics in 1998.  Dr. Thieme is board-certified by the American Board of Pediatrics and is also a fellow of the American Academy of Pediatrics. She has been selected as one of America’s Top Pediatricians by the Consumers’ Research Council of America. Dr. Thieme was Vice-Chairman of Pediatrics at Sky Ridge Medical Center from 2003 – 2005. With her strong interest in the current health care crisis in this country she serves as a delegate for the Colorado Medical Society.

Dr. Thieme’s interests include infants and children of all ages, children with underlying illness, such as heart disease, asthma, kidney disease, congenital defects, premature infants, multiples and children with special needs.

In her spare time, she enjoys spending time with her son, who is a graduate student at the University of Minnesota. She also enjoys bicycle riding, cooking and gardening.

Stacy J. Ostapko, MD, FAAP


Dr. Ostapko graduated from SUNY Upstate Medical University in 2000. She completed her Pediatrics residency in 2003 from Eastern Virginia Medical School in Norfolk, VA, at the Children’s Hospital of the King’s Daughters. She joined the faculty at the medical school following graduation and became involved in the following aspects of pediatric care: children’s emergency care, attending high risk deliveries, inpatient nursery care, and providing gynecological care to inpatient psychiatric patients.
In 2005 she joined an outpatient pediatric practice where she remained until 2010. After marrying, she relocated to Georgia and practiced as a hospitalist and faculty member of the Pediatrics Department at Mercer Medical School in The  Children’s Hospital of Central Georgia. She moved to Colorado in 2013 and joined the pediatric practice here at Castle Rock Pediatrics in 2015.
Dr. Ostapko’s interest in pediatrics include newborn care through adolescence, especially gynecological care, ADHD, eczema, and asthma.  Dr. Ostapko’s interests outside the office include spending time with her husband, two children and one cat, gardening, dancing, horseback riding and exploring this wild and beautiful state.

Randal E. Williams, PA-C

Randy was born and raised in Colorado and attended Smoky Hill High School.  He then attended Kansas Wesleyan University where he studied Biology and played football for the “Coyotes.”

Randy returned home to Colorado and attended the Child Health Associate Physician Assistant Program at the University of Colorado Medical Campus

He currently resides in Castle Rock and has worked at Castle Rock Pediatrics since June of 2012. Randy is also a member of the Pediatric Child Fatality Prevention Team here in Colorado.  His clinical interests include pediatric preventative medicine, pediatric sports medicine, pediatric orthopedics, and pediatric dermatology.  Randy also enjoys teaching PA/medical students in the clinic.where he earned his Physician Assistant Certification in June of 2000.

Randy enjoys working out at the gym, playing sports, going camping, and riding his Harley Davidson Motorcycle.

Dr. Caroline Kabel-Kotler DO

Dr. Caroline Kable-Kotler is a Board Certified Pediatrician who recently joined Castle Rock Pediatrics in November, 2018.  Dr. Kotler and her family moved to Colorado from New Jersey in 2017. She received her medical degree from Rowan University School of Osteopathic Medicine.  She completed her Pediatric Internship at the Kennedy Health System in Stratford, NJ and then her Pediatric Residency at The Cooper University Health Center in Camden, New Jersey.

Dr. Caroline Kabel-Kotler, DO loves working in a smaller pediatric practice.  In this setting she can form relationships and bond with the patients and families. She is passionate about providing Pediatric care to children of all ages with a myriad of medical conditions from birth to early adulthood and has a focus in Behavioral Medicine and Educational Advocacy.


In her spare time Dr. Kotler enjoys spending time with her husband of 25 years and their three children.  She and her family love to ski and hike and spend time in the mountains.