Who We Are

Elder woman and her caretaker

Our staff is committed to providing the highest quality care for our patients. 


We are proactive — providing clinical staff to consult with patients about healthy choices.

We are dedicated — following up with patients at night, on weekends and at their homes, if needed.

We believe in empowerment — giving our patients the information they need to make their own healthcare decisions.


Dr. Priyantha Ranaweera

Interventional Cardiologist

Dr. Priyantha Ranaweera is a Harvard-trained interventional cardiologist who works to meet the healthcare needs of the Flint Hills region.


Caring for patients in the Manhattan area since 2007, he created Manhattan Medical Group in 2018 to provide an integrated care model with primary care and specialized care.

Under his leadership, Manhattan Medical Group is dedicated to the long-term success of patients’ health and the community.

Dr. Ranaweera specializes in:

  • Peripheral interventions

  • Device implantation

  • Heart catheterizations

Dr. Priyantha Ranaweera, owner of Manhattan Medical Group

Dr. Robert Callahan



Robert Callahan D.O. is a Board-Certified Family Physician who is dedicated to delivering comprehensive patient centered care for all ages.  He has spent the last 7 years on Active Duty in the US Army as a physician where he has delivered the full spectrum of primary care services to include: well visits for all age ranges, sports medicine, osteopathic manipulative medicine, most primary care dermatologic procedures, well woman care and contraceptive management, OB care and deliveries, inpatient care, preventative medicine counseling, and a variety of other outpatient procedures. 


Dr. Callahan grew up in the Pacific Northwest and is a former college athlete in the sport of Water Polo.  He trained at the Family Medicine Residency at Martin Army Community Hospital on Fort Benning and has been stationed locally at Fort Riley the last 4 years where he and his wife, along with their 2 children, fell in love with Manhattan. 


Dr. Callahan is extremely excited to be joining the team at the Manhattan Medical Group in order to use his skills and expertise to make a positive impact on his local community.

Larry Pierce 

Physician Assistant

Larry Pierce PA-C, is a certified Physician Assistant who is excited to bring his many years of experience to primary care.

Larry served in the United States Army for 21 years. 10 of those years he spent in family practice as a Physician Assistant. Larry spent 10 years in the Operating Room assisting in various surgical specialties before attending the Inter-service Physician Assistant Program.  He was awarded his Master’s Degree in Physician Assistant Studies from the University of Nebraska Medical Center in 2010.  He went on to attend the U.S. Army Flight Surgeon course at Fort Rucker, Alabama in 2014.

Larry, his wife Kathryn and 4 children fell in love with Kansas when he was stationed here during his clinical rotations and decided to make the Manhattan area their permanent home when he retired.  Larry is a 3rd degree Black Belt in Taekwondo and teaches at J.C. Taekwondo in Junction City.  He is an avid outdoorsman and enjoys spending time in the woods or on the lake when he is not taking care of his patients.   


Becca Haugaard

Nurse Practitioner

Becca Haugaard, APRN-FNP is certified in both wound care and foot care. Becca leads our Wound Care Clinic.


She specializes in;

  • Compression therapy

  • Sharps debridement

  • Adjunct therapy including human skin equivalents and wound vac.

She is also certified to do routine foot care and can provide diabetic foot checks and diabetic foot care.

Together with our vascular specialists, she also provides surgical debridement of non-healing wounds.

head shot Becca.jpg

Abby Suddarth

Physician Assistant

Abby Suddarth, PA-C, is a certified Physician Assistant who is excited to offer virtual telehealth appointments.

She graduated from the Butler University Physician Assistant Program with a bachelor’s degree in health sciences. She initially joined Dr. Ranaweera at Mercy Regional in the fall of 2007 when her husband was stationed at Fort Riley. She has also worked in Internal Medicine and Soldier Readiness Processing..

She enjoys spending time with her family, homeschooling their three girls, practicing her photography skills, reading, and exercising.

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Tyson Nickelson

Nurse Practitioner

Tyson Nickelson, MSN, FNP-C is an advanced practice nursing provider with extensive experience in healthcare, particularly in the care of cardiac patients and in the Intensive Care Unit.

He specializes in:

  • Cardiology

  • Diseases affecting veins

Tyson Nickelson, Nurse practitioner

Hollie Hall

Nurse Practitioner

Hollie Hall, NP-C, specializes in cardiology and diseases affecting veins.

She specializes in:

  • Radio-frequency ablations

  • Sclerotherapy

She graduated from Baker University with a degree in nursing and received a master's degree from the University of Phoenix.

She began her career in the cardiology department of Via Christi Hospital in 2011. She joined Heart and Vascular Clinics in 2016.

She is married to former NFL and Kansas State football alum Joe Hall. They have 4 children: Joe, Jorryn, Joss and Jagger. She enjoys spending time with her family and can be found cheering at her children's sporting events.

Hollie Hall, NP-C

Amanda Nall

Nurse Practitioner

Amanda Nall, NP-C, is an advanced practice provider with extensive experience in healthcare.

She specializes in cardiology and diseases affecting veins.


Joshua Wichman

Nurse Practitioner

Joshua Wichman, NP-C, is an advanced practice provider that specializes in cardiology and disease affecting the veins. 

He joined Manhattan Medical Group in 2021. Josh is currently accepting new patients at our cardiology practice.

Our Clinics

MMG Primary Care

2900 Amherst Ave.

Manhattan, KS 66503


Hours: 8am-5pm Monday-Friday

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Wound Care Clinic - Manhattan

2900 Amherst Ave.

Manhattan, KS 66503


Hours: 8am-4pm Monday-Thursday

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Heart and Vascular Clinics - Manhattan

200 Research Dr.

Manhattan, KS 66503


Hours: 8am-5pm Monday-Thursday

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Outreach clinics in Abilene, Clay Center, Council Grove, Junction City & Wamego

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Vein Clinic of Kansas - Manhattan

2900 Amherst Ave.

Manhattan, KS 66503


Hours: 8am-5pm Monday-Thursday

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Outreach clinic in Junction City

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