Dr. Still is a board-certified and fellowship-trained specialist in nutrition and weight management. His clinical and research interests include malnutrition and comprehensive weight management. Dr. Still obtained his medical degree from the Philadelphia College of Osteopathic Medicine. He completed his residency and a fellowship in clinical nutrition at Geisinger Medical Center. Dr. Still is certified by the American Board of Internal Medicine.|Are weight loss medications right for you? Learn more from Dr. Still. Dr. Still is rated as a Distinguished provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Obesity, Malnutrition, Small Bowel Bacterial Overgrowth, Gastric Bypass, and Vagotomy.

Dr. Hosterman is a board-certified and fellowship-trained specialist in nutrition and weight management. Her clinical interests include adult and pediatric malnutrition and comprehensive weight management. Dr. Hosterman attended the Philadelphia College of Osteopathic Medicine, where she received her medical degree. She completed her internal medicine – pediatric residency and then her weight management and nutrition fellowship at Geisinger Medical Center. Dr. Hosterman is certified by the American Board of Internal Medicine, the American Board of Pediatrics, the American Board of Obesity Medicine and the American Board of Physician Nutrition Specialists. Dr. Hosterman is rated as a Distinguished provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Malnutrition, Short Bowel Syndrome, Small Bowel Bacterial Overgrowth, and Protein Deficiency.

Daniela Hangan is a primary care provider, practicing in Family Medicine in Danville, Pennsylvania. Dr. Hangan is rated as a Distinguished provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Malnutrition, Small Bowel Bacterial Overgrowth, Short Bowel Syndrome, and Obesity.

Susan Rasul is a primary care provider, practicing in Gastroenterologist in Danville, Pennsylvania. Dr. Rasul is rated as an Advanced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Malnutrition, Small Bowel Bacterial Overgrowth, Short Bowel Syndrome, and Obesity.

Anthony T. Petrick, MD, FACS, FASMBS, is a board-certified general surgeon specializing in esophageal and bariatric surgery. Dr. Petrick performs a number of advanced and specialized surgical procedures including advanced endoscopy, revisional bariatric surgery, laparoscopic gastric band (or “lap band”), gastric bypass, biliopancreatic diversion with duodenal switch and gastric sleeve. He also treats people for various conditions affecting the stomach and gastrointestinal (GI) system, including hiatal and paraesophageal hernia, achalasia and acid reflux (GERD).|Board-certified in general surgery, Dr. Petrick earned his medical degree from Georgetown University in Washington, D.C. He completed general surgery residency at Georgetown University Medical Center in Washington, D.C. He then completed a fellowships in Surgical Oncology at and Beth Israel Deaconess Medical Center in Boston and in Bariatric and Foregut surgery at the University of Pittsburgh Medical Center.|For the past 18 years, Dr. Petrick served as program director for the Geisinger bariatric and foregut surgical fellowship. He now serves as associate program director, acting as a mentor to bariatric surgery fellows. Dr. Petrick has a strong commitment to research in bariatric and foregut surgery and has authored more than 100 articles. Currently, he serves as chief quality officer for inpatient services at Geisinger and Director of the Division of Bariatric and Foregut surgery.|Dr. Petrick is an active member of the Society of Gastrointestinal and Endoscopic Surgeons and a fellow of the American College of Surgeons and American Society of Metabolic and Bariatric Surgeons. He chairs to Data and Quality Committee for the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program and also serves as an editorial board member for the journal Surgical and Obesity-Related Diseases and a columnist for Bariatric Times.|In his free time, Dr. Petrick serves on the board of education at St. Joseph School in Danville. He also coaches the Susquehanna Valley Stampede varsity and junior varsity ice hockey teams.|Clinical Focus: Bariatric Surgery|If you’re a provider who’d like to refer a patient, call our 24/7 referral line at 800-332-8901 or visit www.emr-link.com. Dr. Petrick is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Obesity, Hiatal Hernia, Hernia, Gastric Bypass, and Endoscopy.

Christine Hanna is a primary care provider, practicing in Gastroenterologist in Danville, Pennsylvania. Dr. Hanna has been practicing medicine for over 10 years and is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Malnutrition, Obesity, Short Bowel Syndrome, and Small Bowel Bacterial Overgrowth.

David M. Parker, MD, FACS, FASMBS, is a board-certified general surgeon specializing in bariatric surgery for both adolescents and adults. Dr. Parker performs several advanced and specialized surgical procedures, including gastric bypass, biliopancreatic diversion with duodenal switch, revisional bariatric surgery, laparoscopic gastric band (or “lap band”) and gastric sleeve. He also provides care for various conditions affecting the stomach and gastrointestinal (GI) system, including hiatal hernia, paraesophageal hernia, achalasia and acid reflux.|He has a clinical interest in minimally invasive laparoscopic and robotic surgery.|Board-certified in general surgery, Dr. Parker earned his medical degree from West Virginia University in Morgantown. He completed a general surgery residency at the Dwight D. Eisenhower Army Medical Center in Fort Gordon, GA, followed by a fellowship in bariatric and foregut surgery at Geisinger Medical Center in Danville.|While in medical school, he received the Presidential Award for Excellence in Scholarship. During his fellowship, he received the SAGES Award for best fellow presentation.|Dr. Parker serves as program director for the Geisinger bariatric and foregut surgical fellowship. He has a strong commitment to research in bariatric and foregut surgery and has authored more than 24 published articles.|He is an active member of the Society of Gastrointestinal and Endoscopic Surgeons and a fellow of the American College of Surgeons and American Society of Metabolic and Bariatric Surgeons.|Dr. Parker has served in the United States Army and continues to serve as a lieutenant colonel in the United States Army Reserve. He is also a football enthusiast, rooting for the West Virginia Mountaineers in his free time. Dr. Parker is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Hiatal Hernia, Hernia, Obesity, Gastric Bypass, and Endoscopy.

Dr. Shellenberger is a board-certified and fellowship-trained gastroenterologist. His clinical interests include postgraduate medical education, esophageal motility and other GI laboratory procedures. Dr. Shellenberger earned his medical degree from the Philadelphia College of Osteopathic Medicine. He completed his residency and his fellowship in gastroenterology at Geisinger Medical Center. Dr. Shellenberger is certified by the American Board of Internal Medicine in internal medicine and gastroenterology. Dr. Shellenberger is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Crohn's Disease, Angiodysplasia of the Colon, Swallowing Difficulty, Endoscopy, and Colonoscopy.

Amitpal Singh Johal, MD, is a board-certified and fellowship-trained gastroenterologist, also known as a GI doctor. He has a special interest in endoscopic ultrasound, a minimally invasive procedure used to evaluate and diagnose digestive diseases.|Dr. Johal earned his medical degree from the Medical College of Wisconsin. He completed his residency in internal medicine at University Hospitals Case Medical Center in Cleveland and his fellowship in gastroenterology at Geisinger Medical Center.|Dr. Johal is certified by the American Board of Internal Medicine in gastroenterology. Dr. Johal is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Nonalcoholic Steatohepatitis (NASH), Benign Esophageal Stricture, Lower Esophageal Ring, Endoscopy, and Colonoscopy.

Dr. Dinko is a board-certified physician specializing in family medicine. He attended The Commonwealth Medical College, where he received his medical degree, and completed his residency at Washington Hospital. Dr. Dinko is certified by the American Board of Family Medicine.|Outside of work, Dr. Dinko enjoys sports. He also likes spending time outdoors, particularly hiking. Dr. Dinko is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), Nephrosclerosis, and Renovascular Hypertension.

Dr. Sundaresan is a board-certified physician specializing in pediatrics and internal medicine. Her clinical interests include preventive care and chronic disease management. Dr. Sundaresan attended Christian Medical College, Vellore, where she earned her degree in medicine. She completed her residency at Geisinger Medical Center. She is certified by the American Board of Pediatrics and by the American Board of Internal Medicine. Dr. Sundaresan is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Sinusitis, Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), and Relapsing Multiple Sclerosis (RMS).

Dr. Beichner is a board-eligible physician specializing in family medicine. Her clinical interests include hormonal treatment for adult transgender patients (18 years old and up). She attended Jefferson Medical College of Thomas Jefferson University, where she earned her medical degree. Dr. Beichner completed her residency at Washington Hospital. Dr. Beichner is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), Acquired Agranulocytosis, and Hypertension.

Thomas Morland, MD, is a board-certified physician specializing in internal medicine. Dr. Morland has a special interest in preventing chronic illness through lifestyle changes.|“I enjoy working with patients on intensive prevention and placing lifestyle first,” he says. “I find that by incorporating whole foods into their diets, getting more exercise, improving sleep and managing stress, patients can stabilize or even reverse chronic medical conditions and decrease their reliance on medications.”|Dr. Morland attended Yale University, where he received his medical degree, and completed his residency at the Hospital of the University of Pennsylvania. Dr. Morland is certified by the American Board of Internal Medicine and the American College of Lifestyle Medicine.|“The best part of my job is seeing a patient exceed expectations,” he says. “It's great to provide the ‘standard of care,’ but when a patient takes their health into their own hands and collaborates with their healthcare team, we can see patients achieve things they never thought possible.”|Dr. Morland enjoys spending time with his wife and three children, playing the string bass and piano, hiking, playing soccer and swimming. His family has an organic garden in their backyard where “we try to put our own advice into practice,” he says. Dr. Morland is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), Pulmonary Embolism, Shwartzman Phenomenon, and Coronary Artery Bypass Graft (CABG).

Mark Lentz, MD, is an internal medicine physician who provides comprehensive care for adults. He’s passionate about supporting his patients’ long-term health and well-being through preventive care, chronic illness management and timely treatment of new or acute conditions — large or small.|With decades of experience, Dr. Lentz has developed deep clinical expertise in managing a wide range of adult health concerns, particularly chronic conditions such as arthritis, diabetes and heart disease. He also has a special interest in helping patients manage restless legs syndrome.|Originally from Indiana, Pennsylvania, Dr. Lentz earned his medical degree from Thomas Jefferson University and completed his residency at Allegheny General Hospital. He is a Fellow of the American College of Physicians, a recognition of his dedication to delivering the highest standard of care.|Dr. Lentz is known for his thoughtful, patient-first approach and his genuine desire to make a meaningful difference in the lives of those he serves. Dr. Lentz is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Anaplastic Thyroid Cancer, Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), and Glutaric Acidemia Type 2.

David Rolston, MD, is chair of the Department of Medicine Specialties for the Medicine Institute and director of the Division of General Internal Medicine at Geisinger Medical Center in Danville.|Dr. Rolston received his medical training and degree at the Christian Medical College, Vellore, University of Madras, India. He completed his residency at Hahnemann University Hospital in Philadelphia, and was chief medical resident at Hahnemann and at Crozer Chester Medical Center in Pennsylvania. He was elected to the Alpha Omega Alpha Honor Medical Society. After his residency, he was an attending physician and codirector of the internal medicine residency program at Graduate Hospital in Philadelphia. Dr. Rolston then became a staff physician at the Cleveland Clinic, Cleveland, Ohio, where he served as director of the Internal Medicine A91 Clinic, associate program director of the residency program in internal medicine, director of the physical diagnosis curriculum at the Cleveland Clinic Lerner College of Medicine and deputy editor of the Cleveland Clinic Journal of Medicine. He served as treasurer/secretary of the Ohio branch of the American College of Physicians. At Geisinger, he serves on several institutional committees and is part of the governing body for MyCode®.|Dr. Rolston is an editor and reviewer for national and international scientific journals and has published more than 150 manuscripts, abstracts and book chapters. He was the recipient of the prestigious Wellcome Trust Fellowship and has received numerous awards for research and teaching. He has been selected for Best Doctors in America.|Dr. Rolston’s areas of clinical interest include taking care of patients with complex medical problems. His research interests include intestinal water and electrolyte transport, intestinal-related infectious diseases and clinical and basic research as it relates to obesity. Dr. Rolston is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Type 2 Diabetes (T2D), Maturity Onset Diabetes of the Young, Spinal Muscular Atrophy (SMA), Spinal Muscular Atrophy Type 3, and Gastric Bypass.

Osama Shaheen, MD, is a general surgeon specializing in bariatric and foregut surgery. He performs a variety of surgical treatments for adults, including Nissen/Toupet fundoplication, Heller myotomy, laparoscopic hiatal hernia repair, LINX procedure, Roux-en-Y gastric bypass (RYGB), gastric sleeve, duodenal switch, single anastomosis duodeno–ileal bypass with sleeve gastrectomy, (SADI-S) and revisional bariatric surgery.|Dr. Shaheen attended Damascus University in Damascus, Syria, where he earned his medical degree. After medical school, he completed a residency at Damascus University Hospital. He followed that with a fellowship in multi-organ abdominal transplant surgery and a residency in general surgery, both at Thomas Jefferson University Hospital in Philadelphia. He also completed a fellowship in bariatric and advanced minimally invasive surgery with the Advanced Laparoscopic Surgery Associates (ALSA) Medical Group in Fresno, California.|He’s received several Excellence in Teaching Awards during his residency and fellowships.|He and his wife Latifa moved to the area in 2023. “I decided to move to Geisinger, a healthcare system known for its superior quality,” he notes. Dr. Shaheen is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Short Bowel Syndrome, Malnutrition, Obesity, Gastrectomy, and Gastric Bypass.

Kendra Boell is a primary care provider, practicing in Family Medicine in Danville, Pennsylvania. Dr. Boell is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Short Bowel Syndrome and Small Bowel Bacterial Overgrowth.

Anthony Billas is a primary care provider, practicing in Family Medicine in Danville, Pennsylvania. Dr. Billas is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Vertebral Artery Dissection, Maturity Onset Diabetes of the Young, Type 2 Diabetes (T2D), and Phlegmasia Cerulea Dolens.

Kyungsook Kim is a primary care provider, practicing in Family Medicine in Danville, Pennsylvania. Dr. Kim is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. Her top areas of expertise are Diabetic Nephropathy, Chronic Obstructive Pulmonary Disease (COPD), Acquired Agranulocytosis, and Maturity Onset Diabetes of the Young.

Mark Guilfoose is a primary care provider, practicing in Family Medicine in Danville, Pennsylvania. Dr. Guilfoose is rated as an Experienced provider by MediFind in the treatment of Short Bowel Syndrome. His top areas of expertise are Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig's Disease), Spinal Muscular Atrophy (SMA), Spinal and Bulbar Muscular Atrophy, and Spinal Muscular Atrophy Type 3.