Dr. Nathani earned his medical degree at the Dow Medical College in Karachi, Pakistan in 1987. He completed his residency in Internal Medicine and fellowship in Gastroenterology at Wayne State University in Detroit, Michigan. He did an additional year of general Hepatology at the same institution and earned the title of Chief Fellow. Dr. Nathani is Board Certified in both Internal Medicine and Gastroenterology by the American Board of Internal Medicine. Dr. Nathani joined Kelsey-Seybold Clinic in 2007 and currently serves as Associate Chief of Department of Gastroenterology and Medical Director of the Ambulatory Surgical Center in Spring. He has authored several publications and national presentations in the field of Gastroenterology and Hepatology.

Care for children with gastrointestinal, liver and nutritional disorders.

At Houston Colon, we specialize in minimally invasive, laparoscopic, and robotic techniques to diagnose and treat the many diseases we encounter. Our surgeons are double board certified and have completed advanced fellowship training in colon and rectal surgery to serve our patients with the most advanced expertise. With locations throughout Houston and Kingwood, we are committed to our patients and are here to help with the most caring, compassionate, and professional environment that we can.

Ayub Hussain, MD, FACG, FACP, is a Kelsey-Seybold Gastroenterology specialist who obtained his medical degree at Allama Iqbal Medical College in Lahore, Punjab, Pakistan, in 1987. Relocating to the United States, Dr. Hussain completed his internship and residency at Highland Hospital/University of Rochester in 1994 and 1996, respectively. Dr. Hussain provides colon cancer screening as well as treatment and condition management for patients with GERD, inflammatory bowel disease, hepatitis, chronic liver disease and cirrhosis, Barrett's esophagus, GI bleeding, esophageal strictures, gallbladder disease, and Crohn's disease. He joined Kelsey-Seybold in January 2024.

Dr. Galler graduated Magna Cum Laude from Duke University with a Bachelor of Science degree in Biology. After earning his medical degree from the University of Kansas in Kansas City, Kansas, he completed his internship and residency in Internal Medicine at the University of Michigan. He completed a Fellowship in Gastroenterology at the University of Chicago Hospitals in Chicago, Illinois. Dr. Galler is board certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine. He is also certified by the National Board of Medical Examiners. He is a member of several medical societies, including the American Gastroenterology Association and the American College of Gastroenterology. Dr. Galler is involved with the American Kennel Society with Scottish Terriers. He shows Scottish Terriers locally and is also involved in the Scottish Terrier Club of Houston.

Kevin K. Yu, MD, MS, is a fellowship-trained gastroenterologist who attended St. Louis University School of Medicine, graduating in 2018. He then completed his Internal Medicine residency at McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth) in 2021. Dr. Yu remained at UTHealth to complete a fellowship in Gastroenterology, Hepatology, and Nutrition in 2025 and joined Kelsey-Seybold in August 2025. In addition to providing colon cancer prevention and endoscopy services, he diagnoses and treats a wide range of conditions, including inflammatory bowel disease, gastric reflux, hepatology, eosinophilic esophagitis, gastrointestinal motility issues, and pancreas conditions.

Wasay Mohajir, DO, is a gastroenterologist at Kelsey-Seybold Clinic. He treats adults with GERD, IBD, liver and pancreatobiliary disease, and other digestive conditions, and performs diagnostic and therapeutic endoscopy. Dr. Mohajir completed training at UTHealth Houston, Columbia University Irving Medical Center/NewYork-Presbyterian, and Baylor Scott & White Medical Center - Round Rock, where he served as chief GI fellow. He joined Kelsey-Seybold in September 2025.

Sheila Rastegari, DO, is a double board-certified gastroenterologist who attended the University of North Texas Health Science Center at Fort Worth, earning her medical degree in 2017. From there, Dr. Rastegari went on to Methodist Dallas Medical Center, completing its Internal Medicine residency program in 2020. She also completed a fellowship in Gastroenterology and Hepatology at Medical City Fort Worth in 2023. As a gastroenterologist, she helps to prevent gastrointestinal tract cancers while also treating a wide variety of conditions including reflux, peptic ulcer disease, inflammatory bowel disease, celiac disease, and liver disease. Dr. Rastegari joined Kelsey-Seybold in January 2025.

In 2003, Dr. Dharia graduated from The University of Texas Southwestern Medical School in Dallas. He went on to complete his residency at UT Southwestern in 2006, and in 2009, completed a fellowship in Digestive and Liver Diseases. Dr. Dharia is a member of the American Gastroenterological Association, American Society for Gastrointestinal Endoscopy and the American College of Gastroenterology. Dr. Dharia is married with two children. When he's not caring for patients, he enjoys spending time with his family, trying new restaurants and enjoying the great outdoors.