After graduating from medical school, Baghdad University in 1994, Dr Thwaini relocated to Jordan where he started his career in Urology at the Royal Medical Services, which is a national tertiary referral center. He acquired FRCS (Ireland) in 1999 and the Jordanian Board in Urology in 2000.
He then moved to Abu Dhabi where he worked for three years as a specialist at SKMC. He acquired the Arab Board in Urology in 2001.
In 2004 he moved to the UK, where he finished his MD degree from Queen Mary University of London. His thesis was on prostate cancer. In 2007 he entered the UK national higher training scheme in urology. This took place in Northern Ireland, where he worked in Belfast City Hospital, Altnagelvin Hospital and Craigavon Hospital, working with regional and national experts in the field. During his training, Dr Thwaini developed specialist interest in urological cancers. He completed his training in 2012 by acquiring the Intercollegiate Specialty Board Certificate in Urology (FRCS-Urology) and he acquired the CCT UK-wide accreditation.