White House officials say first lady Melania Trump is expected to remain hospitalized for the rest of the week following a "long-planned" procedure to treat a benign kidney condition.

The 48-year-old had an embolization procedure Monday morning at Walter Reed National Military Medical Center. President Donald Trump visited her later Monday and tweeted that the procedure was "successful" and that his wife was in "good spirits."

The White House didn't offer any additional details on Mrs. Trump's condition, though Vice President Mike Pence described the procedure as "long-planned."

Two urologists who have no personal knowledge of Mrs. Trump's condition tell The Associated Press the most likely explanation for the procedure is a kind of noncancerous kidney tumor called an angiomyolipoma, which isn't common but tends to occur in middle-aged women.

The White House has cited the first lady's privacy for not offering any additional details on her condition.

Mrs. Trump was last seen in public on Wednesday at a White House event to honor military mothers and spouses for Mother's Day.

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