Photo of Dr. Mark A. Casillas, MD

A colorectal surgeon in Tennessee, Dr. Mark Casillas offers comprehensive care for intestinal diseases that affect the colon, rectum and intestines.


Reviews of Dr. Casillas
Dr. Casillas


See what patients are saying about Dr. Casillas.





  • Recommends
  • Available
  • On Time
  • Friendly
  • Professional
  • Knowledgeable
  • Nice Office
  • Understandable
  • Reachable
  • Helpful Staff

Dr. C was even better than I could have expected. His office was very clean and the staff was friendly and courteous. He was kind and compassionate with a wonderful bedside manner. He was very thorough in going through my history and took his time in getting to know me and my concerns. He was gentle and concerned for my well-being during the exam and procedure. I wouldn't hesitate to go back, and I would recommend him to anyone. Thanks for saving my as$!

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Office of Dr. Casillas See Insurance
of Dr. Casillas


University Colon and Rectal Surgery  

Accepting New Patients?

Yes, Dr. Mark A. Casillas is accepting new patients at this office.


1934 Alcoa Highway, Suite D-370, Knoxville, TN 37920

Office Hours

  Open Lunch Close
Mon 12:00 - 1:00 pm
Tue 12:00 - 1:00 pm
Wed 12:00 - 1:00 pm
Thu 12:00 - 1:00 pm
Fri 12:00 - 1:00 pm

Office Details

Doctor Specialty Colorectal Surgery
Accepting New Patients? Yes
Practice Specialty Colorectal Surgery
Languages Spoken English

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Insurance Accepted  

Please contact the doctor’s office to inquire about insurance.

About Dr. Casillas
Dr. Casillas



Mark A. Casillas, Jr., MD specializes in laparoscopic and robotic colon and rectal surgery for neoplastic and benign disease, transanal endoscopic microsurgery, inflammatory bowel disease including Crohn’s disease and ulcerative colitis, constipation, and functional anorectal disorders.

Dr. Casillas is an Assistant Professor in the Division of Colorectal Surgery in the University of Tennessee Graduate School of Medicine Department of Surgery. He received a Bachelor’s in Microbiology  from the University of Alabama. He completed a Master’s degree in Molecular Biology at the University of Alabama at Birmingham, and earned his Medical Doctorate from the University of Alabama School of Medicine (UAB). He performed his intern year at Brown University School of Medicine and then completed his general surgery training at St. Joseph Mercy Hospital, Ann Arbor. Dr. Casillas completed a subspecialty fellowship in Colon & Rectal Surgery at Indiana University School of Medicine, and joined the faculty of the University of Tennessee Medical Center in 2012.

Dr.  Casillas has written and presented articles and abstracts on a variety of subjects including basic science cancer research, robotic colon and rectal surgery, as well as single incision laparoscopic colon and rectal surgery.

Dr. Casillas is board certified by the American Board of Surgery and board certified by the American Board of Colon and Rectal Surgery.

Dr. Casillas specializes in the diagnosis and treatment of diseases of the colon, rectum, and anus with emphasis on screening and surgical management of colorectal cancer, hemorrhoids, diverticular disease, and inflammatory bowel disease (Crohn's disease and ulcerative colitis). We offer state-of-the-art screening for colon and rectal cancers and treat complex anorectal disorders, including fecal incontinence & sacral nerve stimulation, pelvic floor abnormalities, anal fissures, and fistulas.


Special Interests  

  • Minimally Invasive Colorectal Surgery
  • Robotic Surgery
  • Single Incision Laparoscopic Surgery

Education & Training  

Medical School


  • St. Joseph Mercy HospitalAnn Arbor, MI
    Residency in General Surgery • 2007 - 2011


Languages Spoken  

  • English
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