About Us

Backus Physicians

Backus Physician Services LLC, a practice affiliated with The William W. Backus Hospital, offers a wide range of minimally invasive surgeries for patients.

Four surgeons practice in the Norwichtown Medical Office Building at 12 Case St., Suite 313 – Sergio Casillas, MD, specializing in colon and rectal surgery as well as general surgery; Michael Deren, MD, specializing in thoracic surgery; Juan Escalon, MD, specializing in thoracic surgery; and Mark Tousignant, MD, specializing in general surgery.


Photo of Sergio  Casillas-Romero, MD

Sergio Casillas-Romero, MD

Medical School: LaSalle University
Residency: SUNY Upstate Medical University at Syracuse
Fellowship: The Cleveland Clinic
Internship: SUNY Upstate Medical University at Syracuse
Residency: SUNY Upstate Medical University at Syracuse
Fellowship: The Cleveland Clinic
Internship: SUNY Upstate Medical University at Syracuse


Photo of Michael  Deren, MD

Michael Deren, MD

Undergraduate: Georgetown University
Medical School: Georgetown University School of Medicine
Residency: Yale-New Haven Hospital
Internship: Hartford Hospital,



Photo of Mark  Tousignant, MD

Mark Tousignant, MD

Undergraduate: Stevens Institute of Technology (NJ)
Medical School: Hahnemann University College of Medicine
Internship: Rush University Medical Center
Residency: Robert Wood Johnson University Hospital
Residency: Middlesex Memorial Hospital
Residency: Rush University Medical Center
Medical School: Hahnemann University School of Medicine
Residency: Rush University Medical College
Internship: Rush University Hospital