Henshaw appeared to dislocate his shoulder as he scored his second try of the comfortable win in Dublin, the Leinster back leaving the field with his injured right arm in a sling.
Coach Joe Schmidt had hoped there would be good news about the centre, but scans on Monday confirmed Henshaw would need an operation.
The 24-year-old has already had surgery to correct the problem but that means he will play no further part in the tournament.
News: @henshawrob ruled out of Championship. @tadhgfurlong - minor hamstring & @JackConan1 slight shoulder knock - both should be available for @WelshRugbyUnionmatch. #IREvWAL #TeamOfUs pic.twitter.com/rq8FmInLWk
— Irish Rugby (@IrishRugby) February 12, 2018
There was better news regarding Tadhg Furlong, though, after he limped out of the Italy win.
Scans on the forward showed he had only suffered a "minor hamstring injury" and Ireland expect him to be fit to face Wales at the Aviva Stadium on February 24.