OAKLAND, Calif. — Baltimore Orioles shortstop Cesar Izturis is scheduled to undergo an appendectomy tonight after complaining of severe stomach pains earlier in the day.

Izturis played in Thursday's 3-2 loss to Seattle and accompanied the Orioles to Oakland for a three-game series against the Athletics. But after arriving at the Coliseum early Friday with stomach pain, the 29-year-old Izturis was taken to a hospital for a CT scan.

The tests revealed that Izturis, who was accompanied to the hospital by assistant athletic trainer Brian Ebel, had appendicitis.

"It's something that started yesterday," said Baltimore manager Dave Trembley, who was awaiting an update from the Orioles' training staff. "I saw him in the hotel. He didn't say anything to anybody until he got to the ballpark today."

Izturis, who is batting .260 with one home run and 13 RBIs, also had to be taken out of game with a stomach ailment on Sept. 5, 2004, while with the Los Angeles Dodgers.

Robert Andino, who was acquired from Florida on April 1 in exchange for right-handed pitcher Hayden Penn, started in Izturis' absence and batted ninth against the A's.

Also, the Orioles released veteran left-hander Jamie Walker, ending a mostly disappointing three-year stay with the team.

Walker had a 5.11 earned run average in 12 1-3 innings and was coming off a horrible appearance in Seattle on Tuesday. He gave up two home runs in one inning and was charged with a blown save in the Orioles' 8-2 loss to the Mariners.

Manager Dave Trembley notified Walker of the decision early Friday.

"It's something that had been discussed the last few days," Trembley said. "Obviously his last appearance in Seattle was the one that finalized it. Everybody knows what the numbers are. We just felt we had to try and get somebody that would be more effective. It just wasn't getting done."

Walker, who will turn 38 on July 1, had been used as a left-handed specialist but gave up six runs in his last 6 2-3 innings when the Orioles decided to make a change.

Walker signed a three-year contract with Baltimore as a free agent in 2006 and promptly set a franchise record with 81 appearances in his first season with the Orioles while also recording a career-high seven saves in his first season with the team.

But after finishing 2007 with a 3.23 ERA, he gave up 12 home runs in 38 innings and finished with a 6.87 ERA last season.

"(He) was a great teammate and a tremendous presence on the club for us," Trembley said. "He totally understood and we just left it at that. We'll miss what he brought. I don't think you have to feel sorry for Jamie Walker."

Left-hander Alberto Castillo was called up from Triple-A Norfolk to take Walker's spot in the Orioles' bullpen. Castillo, 33, was 1-0 with two saves and a 3.09 ERA in 24 games in the minors this year.