According to a message on van-halen.com:
"Eddie Van Halen underwent an emergency surgery for a severe bout of Diverticulitis. No further surgeries are needed and a full recovery is expected within 4 - 6 months.
Van Halen's scheduled November 2012 tour of Japan is currently being rescheduled and the band looks forward to seeing and playing for their fans in 2013."
Get well soon, Ed!