Sexton picked up the problem against England and his club Racing Metro claimed he would be out of action for between ten days and six weeks.
But head coach Joe Schmidt has no doubt about Sexton's fitness, saying: "Absolutely. It was a sprained thumb. He finished the game with it. There was a bit of bruising. The bruising is gone."
Meanwhile, Iain Henderson will make his second Ireland start at blindside flanker after Peter O'Mahony failed to recover from injury in the sole change made by Schmidt to his starting line-up.
"If this was the last game in the Six Nations we might have risked Peter," added Schmidt.
"We're muddling our way though that at the moment. [Henderson] is athletic enough to be a No.6"
On Saturday Brian O'Driscoll will win his 140th Test cap, breaking the world record for most international appearances in his final match for Ireland on home soil.
Devin Toner and Paul O'Connell, who again skippers the side, line up at second row in an unchanged front five with Leinster duo Cian Healy and Mike Ross either side of hooker Rory Best.
Alongside Henderson in the back row is Ulster teammate Chris Henry and vice-captain Jamie Heaslip while Conor Murray continues at scrum-half.
O'Driscoll is again partnered by Leinster teammate Gordon D'Arcy while Dave Kearney, Andrew Trimble and Rob Kearney comprise the back three.
There are two changes to the bench with Rhys Ruddock replacing Henderson and Eoin Reddan coming in for Isaac Boss as scrum-half cover.
Look behind the scenes at Ireland's training camp where the latest sports science technology is being used to monitor key athlete data; identify potential injury risks; and improve overall athlete performance.
IRELAND SIDE TO FACE ITALY:
15. Rob Kearney (UCD/Leinster)
14. Andrew Trimble (Ballymena/Ulster)
13. Brian O'Driscoll (UCD/Leinster)
12. Gordon D'Arcy (Lansdowne/Leinster)
11. Dave Kearney (Lansdowne/Leinster)
10. Jonathan Sexton (Racing Metro)
9. Conor Murray (Garryowen/Munster)
1. Cian Healy (Clontarf/Leinster)
2. Rory Best (Banbridge/Ulster)
3. Mike Ross (Clontarf/Leinster)
4. Devin Toner (Lansdowne/Leinster)
5. Paul O'Connell (Young Munster/Munster)
6. Iain Henderson (Ballinahinch/Ulster)
7. Chris Henry (Malone/Ulster)
8. Jamie Heaslip (Dublin University/Leinster)
16. Sean Cronin (St. Mary's College/Leinster)
17. Jack McGrath (St. Mary's College/Leinster)
18. Martin Moore (Lansdowne/Leinster)
19. Rhys Ruddock (St Mary's College/Leinster)
20. Jordi Murphy (Lansdowne/Leinster)
21. Eoin Reddan (Lansdowne/Leinster)
22. Paddy Jackson (Dungannon/Ulster)
23. Fergus McFadden (Old Belvedere/Leinster)