About Us
Since our founding in 2007, Texas Digestive Specialists (initially Gastroenterology Consultants of South Texas) has grown to be the premier digestive health practice serving South Texas, providing Gastroenterology, Colon and Rectal, and Advanced Weight Loss care.
We have a team of highly trained and dedicated healthcare professionals and staff, providing the highest level of care to every patient in a compassionate and timely manner.
Our Mission
Our goal is to restore and protect your digestive health so you can enjoy your life. We do this by accurately diagnosing and treating your current symptoms and helping to prevent future digestive health issues.
Adult Gastroenterology
NOLAN E. PEREZ, MD, FACP, FACG
ADULT CARE
Dr. Perez founded Gastroenterology Consultants of South Texas in July of 2007.
Dr. Perez earned a Bachelor of Arts from the University of Texas at Austin and a Medical Doctorate from the University of Texas Health Science Center at San Antonio. After medical school, Dr. Perez served in the United States Navy as a Medical Corps Officer. He then completed residency training in Internal Medicine at the Regional Academic Health Center in Harlingen and fellowship training in Gastroenterology/Hepatology at Wayne State University/Detroit Medical Center. He is Board Certified in Gastroenterology and is a Fellow of the American College of Physicians and a Fellow of the American College of Gastroenterology. Dr. Perez is an active member of the American Gastroenterological Association (AGA), the American Society for Gastrointestinal Endoscopy (ASGE), the American Medical Association (AMA), the Texas Medical Association (TMA) and the Cameron/Willacy County Medical Society.
Dr. Perez currently serves as a member of the University of Texas System Board of Regents. He is a member of the Harlingen CISD Board of Trustees and a former Chair of the Texas Woman’s University Board of Regents. He serves in the Governing Board of the Holdsworth Center and the Board of Directors of Lone Star National Bank.
Dr. Perez is fluent in both English and Spanish. He is available for consultation in both our Brownsville and Harlingen offices.
NICOLE M. GRIGG-GUTIÉRREZ, MD
ADULT CARE
Dr. Grigg joined Gastroenterology Consultants of South Texas (GCST) in November of 2017.
Dr. Grigg was born and raised in Puerto Rico. She earned a Bachelor of Science from the University of Puerto Rico and a Medical Doctorate from the Universidad Central del Caribe. She completed residency training in Internal Medicine and fellowship training in Gastroenterology, both at the Veteran Affairs Hospital in San Juan, Puerto Rico. She then completed an Advanced Endoscopy Fellowship at the Carolinas Healthcare System in Charlotte, North Carolina. She is board certified in Internal Medicine and Gastroenterology.
In 2016, Dr. Grigg moved to the Rio Grande Valley to join Knapp Gastroenterology in Weslaco, TX. Dr. Grigg is an active member of the American Gastroenterological Association (AGA), American Society of Gastrointestinal Endoscopy (ASGE) and American College of Gastroenterology (ACG). She is also a Clinical Assistant Professor for The UTRGV School of Medicine.
Dr. Grigg-Gutierrez is fluent in both English and Spanish. She is available for consultation in both our Brownsville and Harlingen offices.
SANDEEP T. SAMUEL, MD
ADULT CARE
Dr.Samuel joined Gastroenterology Consultants of South Texas (GCST) in June of 2018
Dr. Samuel earned a Medical Doctorate from Kottayam Medical College and completed General Medicine Post-Graduate training at the Bangalore Medical College and Research Institute in India. He later completed residency training in Internal Medicine in 2014 and fellowship training in Gastroenterology in 2017 at the State University of New York (SUNY) in Buffalo, New York. He is board certified in Internal Medicine and Gastroenterology.
In 2017, Dr. Samuel moved to the Rio Grande Valley to join Texas Gastroenterology Institute in McAllen, Texas. Dr. Samuel is an active member of the American College of Gastroenterology (ACG), the American Society of Gastrointestinal Endoscopy (ASGE), American College of Physicians (ACP), Indian Medical Association (IMA) and the Association of Physicians of India (API). He is also a Clinical Assistant Professor for UTRGV School of Medicine.
Dr. Samuel is available for consultations in both our Harlingen and Brownsville offices.
JASON R. PHILLIPS, MD, FASGE
ADULT CARE
Dr. Phillips joined Gastroenterology Consultants of South Texas (GCST) in October of 2019.
Dr. Phillips earned a Bachelor of Science in Physics from Abilene Christian University and a Medical Doctorate from the University of Texas Medical Branch in Galveston Texas. He completed residency training in Internal Medicine at the Mayo Graduate School of Medicine and fellowship training in Gastroenterology at the University of Michigan. He is board certified in Internal Medicine and Gastroenterology and a Fellow of the American Society of Gastrointestinal Endoscopy.
In 2006, Dr. Phillips founded Phillips Gastroenterology where he practiced for 12 years. In 2018 he became a Senior Staff Physician for Baylor Scott and White in Round Rock Texas. Dr. Phillips is reviewer for board questions and clinical relevancy for the American Board of Internal Medicine. He is a Clinical Assistant Professor for UTRGV School of Medicine as well as for Texas A&M School of Medicine. He is available for consultations in our Harlingen and Brownsville locations.
BRIAN P. RUTLEDGE, MD
ADULT CARE
Dr. Rutledge’s professional interests include endoscopic procedures, gastrointestinal cancer prevention, treatment of gastroesophageal reflux disease, and long-term management of inflammatory bowel disease and chronic liver diseases.
During his training, Dr. Rutledge met his lovely wife Beatriz, who is a native of Edinburg. She introduced him to Texas, and they are very excited to raise their family in the Rio Grande Valley.
Dr. Rutledge received his undergraduate and medical doctorate degrees from Wayne State University, and completed Internal Medicine residency and Gastroenterology fellowship training programs at Detroit Medical Center. A devoted father and husband, he lives an active lifestyle and enjoys recreational golf, tennis, and basketball.
JUAN I. SANCHEZ, MD
ADULT CARE
A native of Edinburg TX, Dr. Sanchez graduated from UT Pan American in 2009 and received his medical doctorate at UT Health Science Center at San Antonio in 2014. He then moved to North Carolina where he completed Internal Medicine residency followed by Gastroenterology fellowship at Duke University Hospital. Additionally, he completed a fellowship in advanced endoscopy at Duke University. Throughout his training at a busy tertiary referral center, Dr. Sanchez has gained exposure to a wide array of complex pathology spanning the entire gastrointestinal tract.
Dr. Sanchez specializes in advanced endoscopic therapeutic procedures, including endoscopic ultrasound, pancreaticobiliary endoscopy, management of gastrointestinal fistulae, and removal of large gastrointestinal polyps. Dr. Sanchez is also trained to provide luminal stenting for patients with blockages of the stomach, duodenum, colon and rectum.
Dr. Castaño
ADULT CARE
Dr. Castaño has lived in the RGV for the last 7 years. He recently completed a gastroenterology (GI) fellowship at the University of Texas Rio Grande Valley (UTRGV) at Doctors Hospital at Renaissance (DHR) in Edinburg.
Dr. Castaño has lived in Texas his entire life. He was born in Dallas, but only lived there briefly before moving to Laredo where he attended elementary school. He was largely raised in Houston where he attended both middle school and high school.
He received a Bachelor of Science from the University of Houston, and Doctor of Medicine from the Universidad Autonoma de Guadalajara in Guadalajara, Jalisco, Mexico. He then completed Internal Medicine residency at UTRGV DHR in Edinburg. After residency and prior to his GI fellowship, he worked as an assistant professor of Internal Medicine at UTRGV teaching residents and medical students.
ALLAN G. COATES, DO, FACOI
ADULT CARE
Dr. Coates joined Gastroenterology Consultants of South Texas (GCST) in February of 2019.
Dr. Coates earned a B.S. in Biology from Western Michigan University and a Doctor of Osteopathic Medicine from the College of Osteopathic Medicine & Surgery in Des Moines, Iowa. He completed his internal Medicine Internship and Residency at Grand Rapids Osteopathic Hospital in Grand Rapids, Michigan and fellowship training in Gastroenterology from the University of Michigan Medical Center in Ann Arbor, Michigan. He is board certified in Internal Medicine and Gastroenterology.
He is the founder and CEO of Gastroenterology Associates of Western Michigan and of West Michigan Clinical Research Center. Through W.M.C.R.C., Dr. Coates has participated in several studies for gastroenterology conditions. Dr. Coates is an active member of the American Society for Gastrointestinal Endoscopy (ASGE), the American Osteopathic Association (AOA), Michigan Association of Osteopathic Physicians and Surgeons, as well as a Fellow of the American College of Osteopathic Internal Medicine.
He is available for consultations in our Harlingen and Brownsville offices
OSCAR A. ALVAREZ, MD
ADULT CARE
Dr. Oscar Alvarez is the former Chairman of the GI and Endoscopy Division at the VA clinic in Harlingen. Prior to that he was a gastroenterologist in private practice in McAllen for 10 years. He was previously a Clinical Assistant Professor at UTHSCSA and serves as an Assistant Professor at the Instituto Ciencias de la Salud (CES) in Medellin, Colombia.
Dr. Alvarez received his physician and surgeon degree and completed residency at the Instituto Ciencias de la Salud (CES). He moved to the US in 1988 and completed internal medicine residency at UT Health Science Center in San Antonio (UTHSCSA). He also completed a fellowship in gastroenterology and nutrition, and a fellowship in advanced endoscopy at UTHSCSA. During this time, he created a medical student visiting program for students from CES University in Colombia to visit UTHSCSA, and this program is still thriving today.
Dr. Alvarez is a member of the American College of Gastroenterology and he has published numerous abstracts and articles in peer reviewed medical journals. He has received many honors and awards over his career, including being named a Commendable Alumnus of CES Universidad and a Special Honorary Member of the Medellin Academy of Medicine.
MARIBEL M. DE PONCE, PA-C, MPAS
ADULT CARE
STEPHANY SOSA, NP-C, CCRN
ADULT CARE
Stephany Sosa grew up in Brownsville, Texas. She received a Bachelor of Science in Nursing in 2012 from the University of Texas at Arlington and a Master of Science in Nursing also from the University of Texas at Arlington in 2017. She has been a Certified Family Nurse Practitioner since 2018 and joined Gastroenterology Consultants of South Texas in April of 2018. She is a Basic Life Support and Advanced Cardiovascular Life Support instructor for the American Heart Association.
Stephany previously worked at Valley Regional Medical Center as an Intensive Care Unit Nurse from 2012-2018 and as a Nationally Certified/ EMT-Paramedic from 2013-2010 as well as an International Trauma Life Support Advanced Provider from 2010-2017. Stephany is an active member of the Critical Care Nurse Association, the National Nurses United Organization and the American Nurses Association.
MICHELLE LOPEZ, FNP
ADULT CARE
Stephany Sosa grew up in Brownsville, Texas. She received a Bachelor of Science in Nursing in 2012 from the University of Texas at Arlington and a Master of Science in Nursing also from the University of Texas at Arlington in 2017. She has been a Certified Family Nurse Practitioner since 2018 and joined Gastroenterology Consultants of South Texas in April of 2018. She is a Basic Life Support and Advanced Cardiovascular Life Support instructor for the American Heart Association.
Stephany previously worked at Valley Regional Medical Center as an Intensive Care Unit Nurse from 2012-2018 and as a Nationally Certified/ EMT-Paramedic from 2013-2010 as well as an International Trauma Life Support Advanced Provider from 2010-2017. Stephany is an active member of the Critical Care Nurse Association, the National Nurses United Organization and the American Nurses Association.
MIRIAM DE LEON, PA-C,MPAS
ADULT CARE
ANA AGUAYO, PA-C
ADULT CARE
DANIELA RIVAS, FNP
ADULT CARE
LISA BRIONES, PA-C
ADULT CARE
NADIA LOZANO, FNP
ADULT CARE
Pediatric GASTROENTEROLOGY
MIHAELA RINGHEANU, MD
PEDIATRIC CARE
Dr. Ringheanu joined Gastroenterology Consultants of South Texas (GCST) in July of 2019.
Dr. Ringheanu was born and raised in Romania. She earned a Medical Doctorate from Universitatea De Medicina Si Farmacie in Burcharest, Romania. She completed her Pediatric Residency at Maimonides Medical Center in New York, NY and fellowship training in Pediatric Gastroenterology at North Shore University Hospital in Manhasset, NY. Dr. Ringheanu is Board Certified in Pediatrics and Pediatric Gastroenterology.
In 2003, Dr. Ringheanu moved to the Rio Grande Valley to join Harlingen Physician Network in Harlingen, TX. In 2008, she founded GI Care for Kids. Dr. Ringheanu has been a Member of the American Academy of Pediatrics since 1997. She is a member of the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition and a Clinical Assistant Professor for UTRGV School of Medicine.
Dr. Ringheanu is available for consultations in our Harlingen or Edinburg locations.
JESUS MEDINA, PA-C
PEDIATRIC CARE
Erika Tidwell, FNP-C
PEDIATRIC CARE
ColoN & rectal Surgery
ALBERTO PEÑA, MD, FACS, FASCRS
COLON AND RECTAL SURGERY
Dr. Alberto Peña is board certified in colon and rectal surgery. With over 13 years of experience, he specializes in the diagnosis and treatment of disorders of the colon, rectum and anus, using minimally invasive and robotic surgical procedures. He also performs diagnostic colonoscopy, anorectal physiology and treats fecal incontinence.
Dr. Peña received his medical degree from University of Texas Health Science Center at San Antonio. He completed residency training in general surgery at Methodist Health System in Dallas, TX., and colon and rectal surgery fellowship training at the University of Southern California.
DUSTIN LUEBBERS, MD
COLON AND RECTAL SURGERY
Dr. Luebbers is fellowship trained in colon and rectal surgery. He specializes in minimally-invasive and robotic surgical treatment of a wide array of conditions including cancers of the colon, rectum and anus, hemorrhoids, anal fissures, fistulas, diverticulitis, Crohn’s disease, ulcerative colitis, rectal prolapse, pilonidal cysts, anal condyloma, and fecal incontinence.
Dr. Luebbers earned his medical degree at the American University of the Caribbean. He completed a general surgery residency at the University of Texas Rio Grande Valley and a fellowship in colon and rectal surgery at Brown University.
VERONICA MESQUITIC, FNP
COLON & RECTAL SURGERY
ADRIANA NASH, FNP
COLON & RECTAL SURGERY
METABOLIC AND FOREGUT SURGERY
MICHAEL J. MARTINEZ, MD
ADVANCED LAPAROSCOPIC & BARIATRIC SURGERY, ADVANCED WEIGHT LOSS CENTER
Dr. Michael J. Martinez is a native of the Rio Grande Valley. He completed undergraduate studies at Princeton University and earned his medical degree from Yale School of Medicine. Dr. Martinez returned to Texas to complete general surgery training at Baylor Scott and White, and then completed specialty training in the area of minimally-invasive and bariatric surgery at the University of South Florida at Tampa General Hospital. He is board certified by the American College of Surgeons and is a Fellow of the American College of Surgeons and the American Society of Metabolic and Bariatric Surgeons. Dr. Martinez is an advanced minimally-invasive weight loss surgeon using robotic, laparoscopic and endoscopic techniques for treatment of his patients. He is also an accomplished foregut surgeon specializing in gastro-esophageal reflux, gastroparesis and achalasia. He is an Assistant Associate Program Director for the University of Texas Rio Grande Valley General Surgery Residency program.
