In a statement, his office said, "On Sunday, Senator McCain was admitted to Mayo Clinic in Phoenix, Arizona, and underwent surgery to treat an intestinal infection related to diverticulitis."
The statement also included a progress report on McCain's treatment and condition while he's been recovering in his home state.
"Over the last few months, Senator McCain has been participating in physical therapy at his home in Cornville, Arizona, as he recovers from the side effects of cancer treatment. He has remained engaged on his work as Chairman of the Senate Armed Services Committee, and has enjoyed frequent visits from his family, friends, staff and Senate colleagues. Senator McCain and his family are grateful to the senator's excellent care team, and appreciate the support and prayers they continue to receive from people all over the country."
McCain, 81, made public last summer his brain cancer diagnosis, and he's been recovering from side effects of the cancer treatment at his home in Arizona since late last year. While he's been away from Washington, he's continued to be involved with current events, including President Donald Trump's handling of Syria.