The Republic of Ireland international moved to the Reebok Stadium on a free transfer last summer and scored four times in 30 appearances.
But the last of those came during January's 0-0 draw with Crystal Palace as Achilles and thigh complaints took a severe toll.
"I've been in regular contact with Keith and getting regular updates from over there, so I've got a good idea where he is in terms of rehabilitation," Wanderers' head of sports development Mark Leather told The Bolton News.
"He has gone over there with the blessing of the club and, to be fair, there have been a lot of changes here over the summer so we were all in and out - it's probably best for him that he goes somewhere like that and focusses fully on the task at hand.
"I'd imagine it was a great source of frustration to him that he missed such a large chunk of last season so he will be looking to push on soon and will be ready to go."
- Sports & Recreation