Rej has been working as a Consultant Orthopaedic and Trauma Surgeon in London since 2012. He trained at St. Mary’s Hospital medical school (now Imperial College) and has undergone Orthopaedic surgical training both domestically and abroad. He has a First-Class Honours in Orthopaedic Sciences as well as an Orthopaedic PhD for which he received the Gold medal for best new innovative technology in 1999. He has authored multiple papers and books in the field of Global Health, Orthopaedics and Trauma. He was an editor at the British Medical Journal and has an interest in Health Technology and Artificial Intelligence for the benefit of patients and scientific applications. He has experience in device regulation, working both in governmental and corporate contexts. Following the Covid-19 pandemic he was honoured to have been appointed as Deputy Lieutenant to the Lord Lieutenancy of Greater London.

In the NHS he works at Barts Health, across the network at the Royal London, Whipps Cross and the Barts Health Orthopaedic Centre in Newham. He was the Clinical Network Director for Trauma and Orthopaedics across the Northeast London Network.