St Nicholas Abbey has suffered a serious setback in his recovery from a major leg operation.

The six-year-old had a bad bout of colic on Thursday for which he has had to have emergency surgery.

"Unfortunately St Nicholas Abbey had a major setback in his recovery during the night, suffering from a bad colic," owners Coolmore tweeted.

"He underwent emergency colic surgery at Fethard Equine Hospital this morning and the prognosis is very guarded at the moment."

On Wednesday, St Nicholas Abbey had complex surgery on a career-ending injury to a pastern.

The six-times Group One winner fractured a leg on the gallops at Aidan O'Brien's Ballydoyle stables on Tuesday morning in preparation for the King George VI And Queen Elizabeth Stakes at Ascot.

A son of champion sire Montjeu, St Nicholas Abbey was champion two-year-old in 2009 when he crowned his season with a blistering display in the Racing Post Trophy at Doncaster.

Among his Group One wins are three successive victories in the Coronation Cup.

He also won twice on the international stage, taking the Breeders' Cup Turf in 2011 and the Dubai Sheema Classic at Meydan in March.