Mark A. Casillas, Jr., MD, MS, FACS, FASCRS

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

Dr. Casillas is an Associate 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.

He 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 American Board of Colon & Rectal Surgery.

Dr. Casillas specializes in the diagnosis and treatment of diseases of the colon, rectum, and anus with emphasis on screening for colon cancer, the 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 incontinence, pelvic floor abnormalities, anal fissures, and fistulas.

A Message from Doctor Casillas

I hope that you find this website helpful and informative. As a specialist in colorectal surgery, I am very aware that people find it difficult to discuss or attend to colon and rectal problems that they may be experiencing. That is why our office is very focused on making you feel comfortable and relaxed about your treatment.

You can be sure that when you visit our office, I will do my best to listen carefully to all of your concerns, and to explain things to you thoroughly and completely.

Along with my friendly, professional staff, I make it a policy to help each patient by first understanding his or her issues and concerns, and then recommending the best, least invasive treatment possible.

We look forward to meeting you!

Mark A. Casillas, Jr., MD, MS, FACS, FASCRS


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Office Location:
1934 Alcoa Highway, Professional
Building D, Suite 370
Knoxville, TN 37920