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About Dr. Krahn

Western Bariatric, AMC is a bariatric surgery provider serving patients in the San Bernardino, Riverside, and surrounding areas of Southern California. Available surgeries and treatments include Roux En Y Laparoscopic Gastric Bypass, Sleeve Gastrectomy, Lap Band, Medical Weight Loss, Body Contouring, and Hiatal Hernia Surgery. Douglas Krahn, MD, FACS is fellowship trained in general surgery and specializes in bariatric surgery. He is strongly dedicated to their patients and want to help each person live the healthy life that they deserve.

When patients arrive at Western Bariatric, AMC, the first goal is helping each person to determine their weight loss needs and goals. The doctors and staff at Western Bariatric, AMC can customize a weight loss plan for each person, whether it involves non-surgical options like the medical weight loss plan or surgical options like laparoscopic gastric bypass. Call to arrange a consultation anytime!

I am a board-certified general and vascular surgeon affiliated with Murrieta Valley Surgery Associates. Raised in Brazil, I'm fluent in Portuguese and Spanish. My passion for science, teaching and helping others led me to medicine, and I discovered my calling in surgery during anatomy class.

After graduating from the Federal University os Santa Catarina in Brazil, I continued my education in New York, completing residency in general surgery and a vascular surgery fellowship on the East Coast. Opting for warmer climate of California, I've been treating vascular diseases for over two decades, cherishing the connection with my patients. I prioritize lasting cardiovascular health beyond surgical interventions. Recently, I joined the faculty at the UHS General Surgery Residency program, where I stay updated on vascular surgery developments while enjoying teaching.

Outside of work, I endulge in cooking, hiking and tennis with family and friends.

Raymund Cordero, MD, is a skilled, dedicated, and board-certified doctor of medicine specializing in general surgery and has been practicing locally for over 20 years. 

In addition to his work at Murrieta Valley Surgery Associates, Dr. Cordero also holds appointments at Inland Valley Regional Medical Center, Rancho Springs Medical Center, Loma Linda University Medical Center Murrieta, Temecula Valley Hospital, and Menifee Valley Hospital. 

Dr. Cordero is a member of the American College of Surgeons (ACS), the American Society of Breast Surgeons (ASBrS), and the Society of Laparoendoscopic Surgeons (SLS). He is certified by the American Board of Surgery (ABS).

When Dr. Cordero isn’t serving patients, he likes watching basketball and soccer. He also enjoys spending time with his two children, who are both interested in pursuing medicine.

Xiujie Wang, MD, FACS, RPVI, is a board-certified vascular surgeon at Murrieta Valley Surgery Associates.

Dr. Wang studied at Shanxi Medical University in Jinzhong, China, earning her medical degree. After graduation, she moved to the United States and completed a surgical residency at St. Mary’s Hospital in Waterbury, Connecticut. She also completed a vascular surgery fellowship at the Icahn School of Medicine at Mount Sinai in New York City.

Dr. Wang brings more than 20 years of vascular surgery experience to the practice. She treats a wide array of conditions but has a special interest in treating peripheral artery disease (PAD), varicose veins, and aneurysms. 

Outside of the office, Dr. Wang holds appointments at several area hospitals, including Inland Valley Regional Medical Center; Rancho Springs Medical Center and Loma Linda University Medical Center; and Temecula Valley Hospital.

Dr. Wang is board-certified in general and vascular surgery by the American Board of Surgery. She’s also a fellow of the American College of Surgeons and a member of the Society of Vascular Surgery and the American Venous Forum.

Dr. Wang welcomes anyone in need of vascular surgery to Murrieta Valley Surgery Associates today. 

Francis Essien, MD, FACS, is a board-certified general surgeon and fellowship trained in minimally invasive and bariatric surgery.

Dr. Essien's zeal for the art and science of medicine and surgery began as a teenager at the University of Ibadan in Nigeria.

An interest in providing excellent patient care brought Dr. Essien to the United States to pursue a natural calling in the surgical specialty.

Passionate about cutting-edge, advanced, minimally invasive, and robotic surgical technology, Dr. Essien’s knowledge and expertise give patients the advantage of a faster recovery. 

The surgeon’s more cosmetic approach also offers less pain and a quicker return to a happier and more productive lifestyle.

Dr. Essien is highly skilled in various procedures, most frequently performing laparoscopic surgery for severe gastroesophageal reflux disease, laparoscopic hernia repairs, hiatal hernia repairs, minimally invasive endocrine surgery, laparoscopic adrenalectomy, and laparoscopic colon resections for benign and malignant conditions.

Dr. Essien also performs laparoscopic sleeve gastrectomy, laparoscopic gastric bypass, and revision bariatric procedures.

With a passion for Bariatric surgery, Dr. Essien helps patients achieve their goals of a healthier weight while eliminating the medical illnesses associated with excessive weight and enjoying a better quality of life.

Dr. Essien believes in an individualized and holistic approach to improving the health and wellness of patients.

Outside of caring for patients, Dr. Essien enjoys spending time with family at home, cooking, traveling, cycling, and playing golf.

Amit Karmur, DO, is the newest vascular surgeon to join Murrieta Valley Surgery Associates (MVSA).

Dr. Karmur graduated from medical school at the Western University of Health Sciences and completed his general surgery residency at Community Memorial Health System in Ventura, California. He then went on to sub-specialize and complete his fellowship in vascular surgery at Harbor-UCLA Medical Center.

Dr. Karmur treats all types of diseases that affect the vascular system. He specializes in both traditional open surgical and minimally invasive endovascular techniques. These include diseases of the carotid arteries, aortic aneurysms, peripheral arterial disease, and dialysis access.

During his spare time, Dr. Karmur likes to travel and learn about new cultures. He also enjoys maintaining his health by working out and staying active by exploring the outdoors. He and his wife are both from the Inland Empire and are excited to be back in the community.

Craig Owens, MD, is a board-certified general surgeon at Murrieta Valley Surgery Associates.

Dr. Owens studied at the Tufts University School of Medicine in Boston, Massachusetts, earning his medical degree. Then, he completed a transitional year internship at St. Elizabeth’s Medical Center in Brighton, Massachusetts.

Before entering private practice, Dr. Owens completed a general surgery residency at the Loma Linda University Health Education Consortium in Loma Linda, California, receiving extensive training in all aspects of surgical care. 

Dr. Owens is knowledgeable in various surgical techniques and specializes in minimally invasive laparoscopic surgery. 

He holds privileges at several area hospitals, including Inland Valley Regional Medical Center; Rancho Springs Medical Center and Loma Linda University Medical Center Murrieta; Temecula Valley Hospital in Temecula, California; and Menifee Valley Hospital.

When he isn’t meeting with patients or performing operations, Dr. Owens enjoys golfing and car racing. He also believes in continuing education and stays abreast of advances in surgical techniques and technologies.

Dr. Owens is board-certified by the American Board of Surgery. He welcomes anyone needing general surgery to Murrieta Valley Surgery Associates today.

Bolaji Nafiu, MD, FACS, is a double-board-certified vascular surgeon at Murrieta Valley Surgery Associates. 

Dr. Nafiu studied at the University of Ibadan College of Medicine in Nigeria, earning his medical degree. After graduation, he moved to the United States. He completed a general surgery residency at the Charles R. Drew University of Medicine and Science in Willowbrook, California, and a vascular surgery fellowship at Yale New Haven Hospital in Connecticut.

As a general and vascular surgeon, Dr. Nafiu treats various medical conditions, including blood clots, carotid artery disease, and chronic venous insufficiency. He also treats aortic aneurysms and peripheral vascular disease.

He holds privileges at several area hospitals, including Inland Valley Regional Medical Center in Wildomar, California; Rancho Springs Medical Center and Loma Linda University Medical Center Murrieta in Murrieta, California; and Temecula Valley Hospital in Temecula, California.

Dr. Nafiu is a fellow of the American College of Surgeons and a member of the Society of Vascular Surgery and the American Venous Forum. He welcomes anyone needing vascular or general surgery to Murrieta Valley Surgery Associates today.

Olivia Mac, MD, is double board certified in general surgery and surgical critical care. 

Dr. Mac grew up in the suburbs of Los Angeles County and attended medical school at the Medical College of Wisconsin in Milwaukee. After medical school, she returned to California to complete her general surgery residency at Arrowhead Regional Medical Center/Kaiser Permanente Fontana and then a surgical critical care fellowship at Arrowhead Regional Medical Center. 

Dr. Mac became a surgeon so that she could use her skills to help others, as surgeons in the past have helped those in her family. 

In her free time outside of the office, Dr. Mac enjoys baking, playing the piano, and playing with her cats.

She looks forward to welcoming both new and returning patients to Murrieta Valley Surgery Associates.

Sarvenaz Nouri, MD, is a board-certified general surgeon with fellowship training in weight loss and bariatric surgery. She is committed to helping patients at Murrieta Valley Surgery Associates achieve long-term weight loss success by providing the most effective and safe surgical techniques. 

Dr. Nouri understands that each patient’s weight loss journey is unique and partners with them to choose a weight loss surgery that best fits their goals, leading to long-lasting weight loss and achieving their best personal health outcomes.

She believes it is a privilege to be part of each of her patient’s weight loss journey. She loves witnessing first-hand how bariatric surgery transforms patients’ lives and improves their health. In addition to performing weight loss surgery, Dr. Nouri performs a variety of abdominal surgeries, including reflux surgery, gallbladder removal surgery, and hernia repair.

Dr. Nouri earned her medical degree from Drexel University College of Medicine in Philadelphia. She completed her residency training in general surgery at Riverside University Health Systems in Southern California. She obtained fellowship training in robotics and bariatric surgery at Reading Tower Health Hospital in Pennsylvania. She also serves as a Robotics medical director at Corona Regional Medical Center.

Outside of work, Dr. Nouri enjoys weightlifting, sailing in the Pacific Ocean, and watching crime dramas on Netflix.

Hege Johnsen, MD, FACS, is a board-certified general surgeon at Murrieta Valley Surgery Associates, providing complete surgical care to patients in Wildomar, Temecula, Hemet, and Menifee, California.

Dr. Johnsen studied at Albert Szent-Gyorgi Medical University in Szeged, Hungary, earning her medical degree. She then moved to the United States and completed a residency in general surgery.

Dr. Johnsen brings more than 20 years of experience to the practice. She specializes in general surgery but has a special interest in breast surgery and inguinal hernia repair without mesh (shouldice procedure).

Outside of Murrieta Valley Surgery Associates, Dr. Johnsen holds appointments at several area hospitals, including Inland Valley Regional Medical Center in Wildomar, California; Rancho Springs Medical Center in Murrieta, California; Menifee Valley Hospital in Menifee, California; and Temecula Valley Hospital in Temecula, California; and Loma Linda University Medical Center. 

Dr. Johnsen is board-certified by the American Board of Surgery and is a Fellow of the American College of Surgeons. She speaks English and Norwegian fluently, allowing her to serve the practice’s diverse clientele. 

Dr. Johnsen welcomes anyone needing general, breast surgery, hernia repair or cholecystectomy to Murrieta Valley Surgery Associates today. 

Raymund Cordero, MD, is a skilled, dedicated, and board-certified doctor of medicine specializing in general surgery and has been practicing locally for over 20 years. 

In addition to his work at Murrieta Valley Surgery Associates, Dr. Cordero also holds appointments at Inland Valley Regional Medical Center, Rancho Springs Medical Center, Loma Linda University Medical Center Murrieta, Temecula Valley Hospital, and Menifee Valley Hospital. 

Dr. Cordero is a member of the American College of Surgeons (ACS), the American Society of Breast Surgeons (ASBrS), and the Society of Laparoendoscopic Surgeons (SLS). He is certified by the American Board of Surgery (ABS).

When Dr. Cordero isn’t serving patients, he likes watching basketball and soccer. He also enjoys spending time with his two children, who are both interested in pursuing medicine.

Brian Tiu, MD, is a board-certified vascular surgeon at Murrieta Valley Surgery Associates.

Dr. Tiu always knew he wanted to be a doctor. Growing up, he volunteered at various hospitals and medical centers, which spurred his interest in medicine.

Dr. Tiu studied at Rutgers New Jersey Medical School in Newark, earning his medical degree. Then, he completed a surgical residency at the State University of New York (SUNY) Downstate Medical Center in Brooklyn and a vascular surgery fellowship at Maimonides Medical Center, also in Brooklyn. 

These experiences inspired Dr. Tiu to pursue a career in vascular surgery. Dr. Tiu thinks vascular surgery is the most interesting field of medicine. As an expert in the field, he does everything from minimally invasive procedures, like angiograms, to open procedures, like removing blockages and performing bypasses.

Dr. Tiu loves making a difference in his patients' lives. He never rushes appointments and makes time to explain each vascular diagnosis in-depth. Specifically, he explains the natural course of diseases, including where they originate, why they occur, and what can be done to improve them.