McShane was taken from the field on a stretcher following a collision with goalkeeper Steve Harper at the KC Stadium and was immediately sent to hospital.
The club have requested follow-up scans to determine the extent of the damage, but they will not be possible until early next week when the swelling has subsided.
Republic of Ireland international McShane is convinced he faces a lengthy spell on the sidelines, though.
He told the Irish Daily Star: "I am out for six months with an ankle ligament injury and micro fracture of the bone.
"I am going for an operation next Monday and I have to get myself right as quickly as I can.
"It's very frustrating to be honest as I was feeling very good. Now I must battle back as quickly as I can."
The news ends a frustrating first season back in the top flight for McShane, who has also suffered hamstring trouble this season and has featured just nine times in the Barclays Premier League.