The 27-year-old Newport Gwent Dragons forward, who has won seven caps and was part of Wales' World Cup squad in New Zealand last autumn, has been sidelined since January due to a neck injury.

But the Dragons have now revealed that "on-going tests" have revealed aorta damage, with possible heart surgery to follow.

Burns made his Wales debut against the Barbarians in Cardiff last June, coming on as a second-half replacement for Huw Bennett.

At the time, he was dual-registered with the Dragons and this season's British and Irish Cup finalists Cross Keys.

Massive shock

Dragons director of rugby Robert Beale paid tribute to Burns, and said his enforced retirement had come as "a massive shock".

Beale said: "Everything Lloyd has achieved in life he has earned through hard work and dedication.

"His enforced retirement from the game has come as a massive shock to Lloyd and his family and will resonate throughout the rugby world.

"I am personally relieved that this serious condition has been identified off the field of play.

"I would therefore like to thank our medical team at the Dragons, staff at the Royal Gwent Hospital in Newport and University of Wales, Cardiff for all their efforts in ensuring Lloyd has, and will continue to receive, the highest standards of care."

Burns first featured for the Dragons during the 2008/09 season, having played for Pontypool and Cross Keys, but injury meant he could play no part in this season's RBS Six Nations Championship when Wales won the title and clinched a Grand Slam.

Burns went to the World Cup as one of three hookers in Wales coach Warren Gatland's squad, featuring alongside Bennett and Ken Owens.