In a statement on the Croatian FA's website, it is suggested that this will mean the 25-year-old will be out of action for at least 10 days, which would rule him out of Spurs' Premier League matches at Blackburn on Wednesday evening and Bolton Wanderers at White Hart Lane on Saturday.
He would also miss Croatia's friendly against the Czech Republic next Wednesday.
It is believed Modric had his inflamed appendix removed on Tuesday evening, while the rest of Harry Redknapp's squad travelled to the North West for their match at Ewood Park.
The Croatian has become a key figure in the Spurs midfield, and his ingenuity would be sorely missed by a Tottenham side who have found goals harder to come by of late.
The news will cause further frustration to White Hart Lane boss Redknapp, who saw his side knocked out of the FA Cup following a humiliating 4-0 defeat at Fulham on Sunday, before failing to secure a deal for a top striker before the closing of the winter transfer window.
Tottenham are already without Younes Kaboul, Ledley King, Gareth Bale, Tom Huddlestone and the suspended Michael Dawson for Wednesday evening's Premier League clash.
