Dr Kelleher is an honours graduate of University College Dublin in 1995. He completed his Internship and Senior House Officer roles in the Mater Misericordiae University Hospital, Dublin and Mayo Clinic, Rochester Minnesota in 1998, the same year he was awarded Membership of the Royal College of Physicians of Ireland.
He entered the Irish Specialist Registrar training programme in Gastroenterology in 1998 and initially spent two years at the Mater Misericordiae University hospital where he developed an initial interest in interventional endoscopy and hepatology. In 2000 he commenced a 2 year research programme at the Center for Liver Disease, Dublin. The focus of this was the molecular transport mechanisms associated with Hereditary Haemochromatosis and the basis of its phenotypic variability. The body of research was presented and published internationally resulting in Doctorate of Medicine award in 2005. The final year of his training in Ireland was at the National Liver Transplant unit in St Vincents University Hospital 2002-2003.
Dr Kelleher moved to further his training at Beth Israel Deaconess Medical Centre, Boston, USA in 2003 and completed fellowships in Interventional Gastroenterology (with Drs Ram Chuttani and Doug Pleskow) and Hepatology (with Dr Nid Afdhal). During this time he also developed research projects in non Invasive measuring of hepatic fibrosis.
Upon completion of his fellowship he became a Consultant Gastroenterologist at Beth Israel Deaconess Medical Centre in 2005 with specific responsibilities to Interventional Endoscopy and Hepatology. Dr Kelleher returned to the Mater in 2006 to take up his role as Consultant Gastroenterologist where he continues to have a special interest in both Interventional Endoscopy (ERCP and EUS) as well as hepatology.