Pique Sous is facing a "critical" 24 hours after suffering an attack of colic.
The Supreme Racing-owned six-year-old was a Grade Two scorer over hurdles last season and was last seen winning on the level at Leopardstown earlier this month.
Trainer Willie Mullins had been hoping to switch back to hurdles for the Open meeting at Cheltenham in November but all plans have been put on the back-burner.
The owners tweeted: "Pique Sous got a colic last night. Bad colitis now. Being treated. All plans on hold next 24 hrs critical #praying."