Care Team - Nashville Surgical Associates

Get to know our surgeons

Meet Our Care Team

At Nashville Surgical Associates, our experienced and highly-skilled surgeons are certified by the American Board of Surgery and are Fellows of the American College of Surgeons. Our team of board-certified and fellowship trained surgeons includes Dr. Jonathan Cohen, Dr. Ray Hargreaves, and Dr. Zachary Callahan. Learn more about our surgeons below.

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Get to know

Dr. Jonathan Cohen

General, Laparoscopic & Cancer Surgery

Dr. Jonathan Cohen performs a wide range of procedures, including those involving: the skin and subcutaneous area, breast, gastrointestinal & proctological, biliary, endocrine, hernia, and much more.

Dr. Jonathan Cohen received his medical degree from the New York University School of Medicine in 1994. He received his bachelor's degree of science in psychobiology, which he obtained from the University of California in 1990. He completed his general surgery residency at North Shore University Hospital.

He performed volunteer work at the UCLA Medical Center from 1985 to 1988. He also volunteered at the Tel-Hashomer Hospital in Israel, as well as the NY School of Medicine, where he served as the Clinical Correlations Instructor.

The Cornell University School of Medicine appointed him as Clinical Instructor from 1995 to 1996. The New York School of Medicine appointed him Clinical Instructor of Surgery in 1996, where he continued until his relocation to Nashville in 1999. Upon arrival in Nashville, Dr. Cohen completed his Fellowship in Laparoscopic Surgery at Vanderbilt University School of Medicine and served as their Clinical Instructor of Surgery from 1999 until 2001.

Dr. Cohen is a member of the American Board of Surgery, a Fellow of the American College of Surgeons. He is also a member of the Society of American Gastrointestinal Endoscopic Surgeons and the Nashville Surgical Society. He is listed in the Best Doctors in America database which represents the top 5 percent of the nation’s practicing board-certified physicians.

In his spare time, Dr. Cohen enjoys spending time with his wonderful family, reading, and traveling.

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Dr. Ray Hargreaves

General, Laparoscopic & Cancer Surgery

Dr. Ray Hargreaves specializes in a wide range of procedures, including those involving: hernias, breast cancer, gallbladder, reflux disease, abdominal surgery, skin lesions & skin cancer, colon/rectal disease, anal problems, laparoscopic surgery, and much more.

Dr. Hargreaves received his medical degree from Vanderbilt University Medical School in 1985. He attended the Franklin and Marshall College in Lancaster, PA where he earned his Bachelors's degree Cum Laude in 1981. While attending college, he was a part of Phi Beta Kappa and a member of the Black Pyramid Society, which is a 13-member honor society.

He completed his surgery residence in General & Peripheral Vascular Surgery at the University of Arizona Health Sciences Center in Tucson. There, he was also nominated for Medical Student-Selected House Officer of the Year for three consecutive years.

Dr. Hargreaves has worked as a surgeon on multiple medical mission trips, including Haiti twice with the Christian Mission of Pignon, under Medical Director, Guy Theodore, MD, FACS. In 2006, he served as Chief Surgeon for Medecins Sans Frontieres (MSF) – better known as “Doctors Without Borders” – whose mission is in Monrovia, Liberia (West Africa).

Dr. Hargreaves is a Fellow of the American College of Surgeons. In his spare time, he enjoys soccer, reading, traveling, and experiencing new cultures and customs.

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Dr. Zachary Callahan

Minimally Invasive General & Bariatric Surgery

Dr. Callahan specializes in minimally invasive general surgery including weight-loss surgery.

He is fellowship-trained in primary and revisional weight-loss surgery including both traditional laparoscopic procedures (sleeve gastrectomy, gastric bypass, duodenal switch) and exciting new incisionless procedures such as endoscopic sleeve gastroplasty, endoscopic revision of gastric bypass, and intragastric balloon placement.

He also offers incisionless treatment of Achalasia, Gastroparesis, Zenker’s Diverticulum, and early-stage cancers of the esophagus or stomach. He has additional training in foregut surgery (hiatal hernia repair and anti-reflux procedures including fundoplication or LINX placement.) Lastly, he offers minimally invasive repair of both simple and complex abdominal wall hernias.

Dr. Callahan graduated Alpha Omega Alpha from the Cincinnati College of Medicine and then joined the Jefferson Surgical Residency in Philadelphia. At Jefferson, he logged over 1,100 general surgery cases and passed both Fundamentals of Laparoscopic and Fundamentals of Endoscopic Surgery examinations. During his time there, he received seven teaching awards, was accepted to the Gold Humanism Honor Society and was selected as Administrative Chief Resident in his final year.

After residency, he matriculated to his first-choice fellowship in Minimally Invasive Surgery (MIS) to train under foregut expert, Dr. Michael Ujiki, at NorthShore University Health System in Chicago. This fellowship is one of only a few programs in the country to be accredited in four categories of MIS training including Advanced GI MIS, Bariatric, Comprehensive Flexible Endoscopy, and Foregut.

Dr. Callahan has presented research at numerous national meetings; he has more than 30 publications and over 200 citations relating to minimally invasive surgery. He is an active member of the Society of American Gastrointestinal and Endoscopic Surgeons and the American Society for Metabolic and Bariatric Surgery.

In his spare time, Dr. Callahan enjoys staying active, traveling, and spending time with his wife and Berne-doodle, “Carson.”

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Patient Testimonials

Nashville Surgical Associates really makes you feel like family.

-G.B.

I appreciate so much your gentle, professional bedside manner. You are an excellent doctor!

-J.B.