General manager Jeff Luhnow couldn't be reached for comment.
Gattis, who hit .246 with 11 triples, 27 homers and 88 RBIs in 2015 in his first season in Houston, said he had been feeling some discomfort for "a while" and that he underwent an MRI after the discomfort worsened about a week ago.
"Within five days I'm in Philadelphia with Dr. [Bill] Meyers," Gattis said. "He has an excellent track record with these core-related injuries."
Gattis lost nearly 20 pounds this winter in an effort to try to play first base or catch this season.
The Astros are scheduled to have an arbitration hearing on Tuesday with Gattis, who is asking for $3.8 million; the club is seeking to pay Gattis $3 million in his first year of arbitration.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.