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UCLA Pediatric Gastroenterology

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Meet our Physicians

 

 Dr. Suzanne McDiarmid

Sue V. McDiarmid, MD 

Professor of Pediatrics and Surgery
Chief, Division of Pediatric Gastroenterology, Hepatology and Nutrition
Program Director, Pediatric Gastroenterology Training Program

Dr. Sue McDiarmid is Professor of Pediatrics and Surgery at The David Geffen School of Medicine at UCLA.  She serves as Chief of the Division of Pediatric Gastroenterology, Hepatology and Nutrition and the Director of the Pediatric Liver Transplant Program at Mattel Children's Hospital UCLA. She is also the Program Director of the Pediatric Gastroenterology Training Program at UCLA.  Dr. McDiarmid is a native of New Zealand and she received her medical degree from the Medical School of the University of Otago in Dunedin, New Zealand.  She completed her residency in pediatric at the Eastern Virginia School of Medicine/Children's Hospital of the King's Daughters and served as a Chief Resident of Pediatric at Valley Medical Center in Fresno, CA.  She completed her fellowship training in pediatric gastroenterology, hepatology and nutrition at UCLA Medical Center.

Dr McDiarmid has a long standing research interest in liver transplantation outcomes and complications, both short and long term, and in the development of new immunosuppressive strategies, including new drug trials and also biomarker studies for immunosuppression minimization. She also is a national advocate for improving access to transplantation for children, including developing the scientific model for the PELD score. She is the Medical Director of the Hand Transplantation Program at UCLA.


Elizabeth Marcus, MD

Assistant Professor of Pediatrics

Dr. Elizabeth Marcus is an Assistant Professor of Pediatrics at The David Geffen School of Medicine at UCLA.  She received a BA in Psychology from Stanford University and her medical degree from the University of Southern California.  She completed her residency in pediatrics at Children's Hospital of Los Angeles and her fellowship in pediatric gastroenterology at UCLA. Her clinical interests include intestinal failure/intestinal transplant, TPN, general GI.

Research interests: Basic science research studying acid acclimation mechanisms and pathogen/host interactions of Helicobacter pylori. H. pylori infects 50% of the world's population and causes gastritis, gastric and duodenal ulcer disease, and gastric cancer. Infection typically occurs in childhood. The bacteria are able to live in the acidic gastric environment by regulating the pH of the periplasmic space, mainly through the use of a cytoplasmic urease enzyme and a pH gated urea channel. Both bacterial and host factors determine who will develop more advanced disease. Study of how H. pylori are able to live in the stomach and which factors increase virulence will lead to improved treatment regimens.  Dr. Marcus has been awarded grants from the NIH as a result of this work.

Current Research Project:

  • Mechanisms of gastric mucosal response to H. pylori infection at acidic pH

Dr. Martin Martin 

Martín G. Martín, MD, MPP

Professor of Pediatrics

Dr. Martín G. Martín is a Professor of Pediatrics in The David Geffen School of Medicine at UCLA.  He received his medical degree and a Master of Public Policy from Harvard and completed his residency in pediatrics at Harbor-UCLA Medical Center and his fellowship in pediatric gastroenterology at UCLA.  His clinical interest is in translational research in Pediatric Intestinal Failure, including chronic diarrheal disorders and intestinal pseudo-obstruction.
 
Dr. Martín's laboratory is interested in investigating the molecular basis of a variety of novel and established congenital malabsorptive diarrheal disorders. He is investigating the role of gut endocrine cells in nutrient absorption and various chronic diarrheal disorders in children. Neurogenin-3 is a transcription factor that is required for the production of islet cells of the pancreas and enteroendocrine cells of the gut. His laboratory described a novel autosomal recessive disorder that is clinically characterized by chronic congenital malabsorptive diarrhea and severe intestinal failure. This disorder was named enteric anendocrinosis and it's significant because it confirms for the first time that enteroendocrine cells have an important role in facilitating nutrient absorption. Since his description of enteric anendocrinosis, he has characterized the clinical phenotype of several other new congenital diarrheal disorders that clinically resembles many of the features of Neurogenin-3 deficiency. These other disorders have either abnormalities of subsets of gut endocrine cells, the process required to convert pro-hormones into functional hormones, and presumably defects in putative hormones that mediate nutrient absorption.
 
Dr. Martín's research team has a collection of nearly 400 kindreds with various forms of intestinal failure and he is currently utilizing total genome (exome) sequencing to identify the molecular basis of several of these disorders.
 
Dr. Martin has also received funding from the California Institute of Regenerative Medicine (CIRM) to generate patient-specific pluripotent stem cells (iPS). These cells are being used to generate intestinal mucosa in the laboratory that are being used to screen putative defective genes that were identified by exome sequencing of subjects with novel diarrheal disorders, and other causes of intestinal failure. Dr. Martin believes that our ability to grow and manipulate intestinal mucosa provides a unique opportunity to study the biology of these various novel diarrheal disorders that is the focus of our laboratory.
 
Dr. Martín's laboratory has also received a UO1 grant on gut stem cells and UCLA is one of 8 NIH funded institutions that are participating in this new consortium. The goal of this project is to isolate human intestinal stem cells, and to define the growth requirements to grow them in both in vitro and in vivo conditions, including growth on biosynthetic scaffolds. Dr. Martín chairs the Translational Applications Strategic Objective Working Group within the consortium.


Dr. Jorge Vargas 

Jorge H. Vargas, MD

Professor of Pediatrics

Dr. Jorge Vargas is Professor of Pediatrics at The David Geffen School of Medicine at UCLA and is the Medical Director for the Parenteral and Enteral Nutrition Support Program at Ronald Reagan UCLA Medical Center.  Dr. Vargas received his medical degree from Colegio Mayor de Nuestra Señora del Rosario in Bogota, Colombia.  He completed his residency in pediatrics at the  Hospital Infantil Lorencita Villegas de Santos in Bogota, Colombia and his fellowship in pediatric gastroenterology at the Hospital Trousseau in Paris and UCLA. His clinical interests include gastrointestinal motility disorders, nutrition, functional bowel disorders and therapeutic endoscopy.

Dr. Vargas' clinical research interest is in gastrointestinal motility disorders.  He is the Director of the Pediatric Gastrointestinal Motility Center at UCLA. The center evaluates, treats and follows patients who have a variety of different gastrointestinal motility disorders


Elaheh (Eli) Vahabnezhad, MD

Associate Physician

Dr. Elaheh (Eli) Vahabnezhad joined the Division of Pediatric Gastroenterology, Hepatology and Nutrition at Mattel Children's Hospital in 2013.  Dr. Vahabnezhad earned a B.S. in Neuroscience from UCLA and attended medical school in New York at the Albert Einstein College of Medicine.  She returned to UCLA for her residency training in pediatrics and completed her fellowship in pediatric gastroenterology, hepatology and nutrition at Mattel Children's Hospital UCLA.  Dr. Vahabnezhad is based at the Pediatric Specialties Practice 12th Street Office in Santa Monica as part of our community outreach.

Dr. Vahabnezhad's clinical interests include inflammatory bowel disease, celiac disease, eosinophilic esophagitis and nutrition.  Her research investigates therapeutic modalities for IBD, specifically infliximab.


Dr. Robert Venick 

Robert Venick, MD

Associate Clinical Professor of Pediatrics

Dr. Robert Venick is an Associate Clinical Professor of Pediatrics and Surgery, and the Medical Director of Intestinal Transplantation at The David Geffen School of Medicine at UCLA. Dr. Venick has been a part of the intestinal failure, liver and intestinal transplant teams at UCLA over the past decade.  His clinical and translational research in intestinal failure has focused on nutritional outcomes and the role of Omega-3 Fatty Acids in intestinal failure associated liver disease. Dr. Venick is pleased to represent UCLA as the site investigator for the Pediatric Intestinal Failure Consortium.  Dr. Venick has received funding from the National Institute of Health and the American Society of Transplantation for his research in liver and intestinal transplant-related pharmacogenomics, medical adherence and post-transplant lymphoproliferative disease.  He has been recognized as a promising young investigator by the Intestinal Transplant Association and the International Liver Transplantation Society, for which he is President of the Vanguard Committee.

Current clinical trials and studies:

  • Intervention after MALT (I-AM) - A pilot intervention using telemetry to improve adherence post transplant
  • A 12-week pharmacokinetic, safety and pharmacodynamic study of teduglutide in pediatric subjects aged 1 year through 17 years, with short bowel syndrome who are dependent on parenteral support
  • Biomarkers for post-transplant lymphoproliferative disorders in children
  • Protocol for the use of oral cisapride in the treatment of pediatric patients with refractory gastroesophageal disease and other gastrointestinal motility disorders
  • Medication adherence in children who had a liver transplant
  • Intestinal failure in children

Dr. Laura Wozniak 

Laura Wozniak, MD, MSHS

Assistant Professor of Pediatrics

Dr. Laura Wozniak is an Assistant Clinical Professor of Pediatrics at The David Geffen School of Medicine at UCLA.  After earning a B.S. in Physiological Sciences from UCLA, Dr. Wozniak attended medical school in New York at the Albert Einstein College of Medicine. She then returned to UCLA for her pediatric residency and gastroenterology fellowship. Dr. Wozniak is board-certified in pediatric gastroenterology and clinical pharmacology. Her clinical interests include liver disease, intestinal failure, liver/intestine transplantation, and nutrition.

During her research time she is working on translational studies and health services projects aimed at improving outcomes for children with liver and intestinal disease. With grant support from the American Association for the Study of Liver Diseases (AASLD) and the UCLA Clinical and Translational Sciences Institute (CTSI), Dr. Wozniak is developing immunogenetic markers of tolerance and rejection that will enable clinicians to optimize the management of immunosuppression in pediatric transplant recipients. She is also studying nutritional outcomes and risk factors for catheter associated bloodstream infections in children on long-term parenteral nutrition.

Current Research Projects:

  • Immune monitoring (development of biomarkers of tolerance and rejection) in pediatric liver and/or intestine transplant recipients
  • Nutritional outcomes in children on home parenteral nutrition
  • Risk factors for bloodstream infections in children on home parenteral nutrition

Dr. David Ziring 

David Ziring, MD

Assistant Professor of Pediatrics

Dr. David Ziring is an Assistant Professor of Pediatrics in The David Geffen School of Medicine at UCLA and is the Medical Director of the UCLA Pediatric IBD Center.  Dr. Ziring received his medical degree from the Chicago Medical School concurrently with earning his Master's degree in Clinical Immunology.  He completed his pediatric residency at Children's Hospital of Orange County and his fellowship in pediatric gastroenterology at UCLA.  Dr. Ziring's clinical interest is in inflammatory bowel disease and is recognized for his translational research and expertise in IBD immunology.

Dr. Ziring serves as the primary investigator and UCLA's representative for the national Pediatric IBD Consortium.  He is involved with nine IRB-approved clinical studies including investigator-initiated, registry, and pharmaceutical sponsored trials. Among these projects are two nationally recognized trials for the PROKIIDS CCFA Pediatric IBD Research Network; the RISK and PROTECT studies, trials that attempt to identify biologic risk factors for the development of complicated Crohn's disease and ulcerative colitis, respectively.  Dr. Ziring is also involved in cutting-edge research in pediatric IBD resulting in the discovery of a new IBD-associated gene (CNR2, a gene involved in the endocannabinoid system) and the importance of this system in regulating the immune system in IBD.

Current clinical trials and studies:

  • A Pilot Study of Autologous Hematopoietic Stem Cell Transplantation with post-transplant ultra low dose IL-2 for refractory Crohn's Disease
  • Predicting Response to Standardized Pediatric Colitis Therapy: The PROTECT Study 
  • A Multicenter, Prospective, Long-term, Observational Registry of Pediatric Patients with Inflammatory Bowel Disease
  • Vitamin D supplementation as non-toxic immunomodulation in children with Crohn's disease 
  • Risk Stratification and Identification of Immunogenetic and Microbial Markers of Rapid Disease Progression in Children with Crohn's Disease 
  • IBD Biobank
  • PediIBD Consortium Registry