The Cammi Calvisano player was excluded from Pierre Berbizier's selection for the World Cup in France 2007.
"It has been a very difficult decision," admitted Scanavacca.
"But considering what has happened recently with the national team, I have lost a lot of enthusiasm to continue playing."
The 33-year-old, who made his national-team debut back in 1999, was surprised to have been left out of the Italy squad after his performances at the Six Nations tournament earlier this year.
Scanavacca played a big part as the Azzurri ensured their most successful campaign since joining the Six Nations in 2000.
He racked up 22 points at Murrayfield in the 37-17 triumph, which marked Italy's first-ever away victory in the tournament.
Scanavacca, who joined Calvisano last summer after 15 years with Rovigo, holds the record of most points scored (3212) in the Italian league.