About – Advanced Endoscopy Centers

Our Mission

At Advanced Endoscopy Centers, our mission is simple: to provide safe, accurate, and compassionate gastrointestinal care in a setting that puts patients at ease. We believe that every person deserves clear answers, reliable procedures, and a team that treats them with respect. From preparation to follow-up, our focus is on making each step clear, supportive, and easy to navigate.

Our Mission

Meet Dr. Homan Zadeh

Dr. Homan Zadeh is a board-certified gastroenterologist with more than 25 years of experience in internal medicine and advanced endoscopic care. He grew up in Palm Springs and graduated from Palm Springs High School. After completing his undergraduate studies at the University of California, Irvine, he earned his medical degree from Wayne State University. He later returned to UC Irvine to complete both his internal medicine residency and gastroenterology fellowship, and also earned a Master’s in Public Health from UCLA.
 
Dr. Zadeh is known for his commitment to delivering thoughtful, high-quality care and for helping patients feel seen, heard, and informed. He currently serves as Section Chief of Gastroenterology and Vice Chairman of Internal Medicine at Desert Regional Medical Center. He also teaches future physicians as an Assistant Clinical Professor of Internal Medicine at Western University, School of Health Sciences.
 
Over the course of his career, Dr. Zadeh has been at the forefront of many important advancements in gastrointestinal care. He was the first in the region to perform a fecal transplant to treat recurrent C. difficile infections and continues to provide specialized care for liver disease, digestive disorders, and preventive screenings.
 
At Advanced Endoscopy Centers, Dr. Zadeh leads with both precision and compassion. His approach is centered on clear communication, clinical excellence, and creating a comfortable experience for every patient. Whether you’re coming in for a routine screening or need support for a more complex issue, Dr. Zadeh’s goal is always the same to help you understand your care and feel confident in your next steps.

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Years of Experience Trusted across the Coachella Valley.

Martin J. Collen, MD, MBA

		Dr. Collen is an internationally recognized physician who was born in Oakland, California and grew up in Los Angeles. During the more than 30 years of Dr. Collen’s training and academic association in medicine, he has authored more than 250 original research and review publications, including books, articles, and abstracts. He graduated with a B.A. in Mathematics from UCLA in 1966, and attended Chicago Medical School at Rosalind Franklin University School of Medicine and Science, Chicago, Illinois, graduating in 1970 with an MD degree. He completed a year of internship in medicine and a year of residency in general surgery at UC, Irvine, and then went on to complete an additional two years of residency in Internal Medicine and two years of fellowship in Gastroenterology at UCLA, finishing in 1977. He was an Assistant Professor of Medicine at UC, Irvine from 1977-1980, and was Instructor of the Year for two successive years. He completed a research fellowship in Gastroenterology from 1980-1985 at the National Institutes of Health in Bethesda, Maryland, and was Associate Professor of Medicine and Director of GI Research at Georgetown University Medical Center in Washington, DC from 1985-1990. He moved back to California in 1990, where he was Professor of Medicine at Loma Linda University from 1990-1995 and Clinical Professor of Medicine from 1995-2005. He earned an Executive MBA in Health Care from UC, Irvine in 1999. Dr. Collen has been in private practice as a Gastroenterologist since 1995. He is board certified in both Internal Medicine and Gastroenterology and is a Fellow of the American College of Physicians and the American College of Gastroenterology.		
	

Vijay Agarwal, MD

Dr Agarwal received his MBBS (Bachelor of Medicine & Bachelor of Surgery) degree in 1977 and MD (Doctor of Medicine) degree in 1981 from Kasturba Medical College, Mangalore, India. He migrated to the USA in 1983. He completed Internal Medicine Residency in 1987 from Framingham (Boston University) and Fellowship in Gastroenterology, Hepatology & Nutrition in 1989 from Veterans Administration Medical Center (Boston University). He joined University of New Mexico Medical Center in June 1989 as Assistant Professor of Medicine (Gastroenterology) and was in charge of Laparoscopy and Motility Studies. During his tenure there, he conducted basic research in “The Role of Short Chain Fatty Acids in Diversion Colitis” and “Role of Nuclear Magnetic Resonance in Hepatic Encephalopathy”. He joined FHP in December 1992 and was Section Chief from June 1993 until early 1996 until FHP closed its Specialty Clinics. He then formed his own practice group in Albuquerque, New Mexico and he practiced there until early 2019 . He performs all diagnostic and therapeutic endoscopic procedures including esophageal manometry, anorectal manometry and capsule endoscopy. He moved to Palm Springs, CA in 2019 to join Dr Homan Zadeh and Dr Martin Collen in their practice.

Mark Gabriel, DO

Dr. Mark Gabriel grew up in Denver, Colorado where he received a Bachelor’s Degree in Biology and Chemistry from the University of Colorado. He then moved to California to attend medical school at the Western University of Health Sciences. His post-graduate training was completed at Loma Linda University in Internal Medicine, followed by serving an additional year as Chief Medical Resident, and then a 3 year fellowship in Gastroenterology.
 
Dr. Gabriel has been practicing gastroenterology since 2000. He has served as associate clinical professor of medicine/gastroenterology at the University of California Riverside, School of Medicine. He now sees patients for gastroenterology-related concerns in La Quinta and Rancho Mirage. In his spare time, Dr. Gabriel enjoys spending time with his wife, family, and cats, cooking, gardening, and playing the guitar.
 
Medical Education: Western University of Health Sciences, DO
Residency: Loma Linda University, Internal Medicine
Fellowship Training: Loma Linda University, Gastroenterology