Loewen is on the 15-day disabled list. He missed most of last year after undergoing surgery on the elbow.
"I'm encouraged that the bone scan came back clear, that's good," Trembley said. "They put a screw in this kid's elbow ... that's more of a rod than a screw. The way [trainer] Richie [Bancells] explained it to me was the bone was split, so they put the screw in to mend it."
But Trembley said again that Loewen will likely return later rather than sooner.
"I wouldn't expect that he's going to pitch when his 15-day DL is done," Trembley said. "It's going to be longer than the 15 days."
Loewen made only six starts in 2007 before a stress fracture was fixed by the surgery Andrews performed. The left-hander was placed on the 15-day disabled list last Friday after going 0-1 with a 7.85 ERA in four starts this year.
The bone scan was done Tuesday after getting a CT scan and MRI on Monday. The exact date which Loewen will see Andrews is still being set up.
The loss of Loewen has forced the Orioles to scramble and make some moves to fill the starting spot and the subsequent holes in the bullpen. Matt Albers, who'd been the long man in the bullpen, made his second start of the season Wednesday.
Trembley also said that the rotation for this weekend's series against the Angels would be Jeremy Guthrie, Daniel Cabrera and Steve Trachsel, but he didn't want to address the subsequent Oakland series just yet.
Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.