His research is primarily focused on functional gastrointestinal disorders, dyspepsia, Helicobacter pylori, gastroesophageal reflux disease, and eosinophilic disorders of the gut. He has recently described (with his team) a new disease entity in adults, eosinophilic duodenitis, linked to functional dyspepsia. His group has documented a genetic component in upper and lower functional bowel diseases. He is considered one of the world's leading authorities in clinical research on the stomach.