"I certainly have faith in the Lord above and the doctors who will be standing by that everything is going to work out just fine," Brennaman said on FOX Sports Ohio.
Jim Kelch, Jim Day and George Grande will be filling in for Brennaman. A return date was not immediately known.
Brennaman, the son of legendary Reds radio voice Marty Brennaman, is in his 10th season calling Reds games and 29th overall calling Major League Baseball games. He thanked the Reds, FOX Sports Ohio and the FOX network for their support.
"They have been incredible during some trying days here recently. It's something that every employee dreams about," he said.
There was also appreciation shown for viewers who have offered well wishes.
"There is no place in this world I'd rather be working and living than my hometown of Cincinnati, Ohio," Brennaman said. "And a big reason why is because of you."
Mark Sheldon has covered the Reds for MLB.com since 2006, and previously covered the Twins from 2001-05. Read his blog, Mark My Word, follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.