Healy flew home from the Lions' historic series victory over Australia this summer after suffering an ankle injury in the midweek victory over Western Force.
And Leinster coach Matt O'Connor admits his prop faces another spell on the sidelines after going under the knife.
"Cian had ankle surgery on Wednesday so he's unavailable for about eight weeks," O'Connor. "He's doing good but he won't play for a while."
Meanwhile Leinster and Lions teammate Sean O'Brien is also a doubt for the return game with Northampton this weekend after suffering a dead leg.
"Sean trained all right so we'll wait and see. We'll give him as long as possible and hopefully he'll be right," added O'Connor.