Professor Riordan is Professor of Medicine (Conjoint) at the Prince of Wales Clinical School, Faculty of Medicine, University of New South Wales and Head of the Gastrointestinal and Liver Unit at the Prince of Wales Hospital, a University Teaching Hospital, in Sydney, Australia.

He holds appointments as Senior Staff Specialist in Gastroenterology and Hepatology at the Prince of Wales Hospital and its affiliated Sydney Children’s Hospital and Royal Hospital for Women (also University Teaching Hospitals) and as Consultant Physician, Gastroenterologist and Hepatologist at the Prince of Wales Private Hospital.