Nats just issued a press release on the matter.

here's the jist:

Washington Nationals General Manager Jim Bowden announced Thursday afternoon that they would place catchers Paul LoDuca (fracture of fourth metacarpal in right hand) and Johnny Estrada (ulnar neuritis in right elbow) on the 15-day DL and expect to recall catcher Jesus Flores from Triple-A Columbus and reactivate outfielder Elijah Dukes from the DL.
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BOTTOM LINE: The team could really use a shot in the arm from Dukes. Both corner outfielders (Wily Mo Pena and Austin Kearns) have been delivering little at the plate and Dukes was swinging the bat pretty well on his rehab assignment.

LoDuca is expected to miss four to six weeks withthe broken hand, and Estrada wasn't helping anyone sitting on the bench unable to throw. Expect Nieves and Flores to pretty much split the catching duties forthe time being.

http://bottomfeederbaseball.blogspot.com/2008/05/nats-dl-loduca-estrada-recall-flores.html