We are told it is a fairly routine procedure.
There have been stylish first ladies throughout the history of the United States, there have even been first ladies who were ex-models, but is Melania Trump (née Knauss) the hottest?
The president was not present during the procedure.
The president spent a little over an hour at Walter Reed National Military Medical Center with his wife Monday evening before departing via motorcade under threat of bad weather.
U.S. media reported that her husband, Donald Trump, is due to visit her in hospital later in the day.
Vice-President Mike Pence said the procedure was long planned.
The East Wing keeping her medical condition private until after the procedure was nothing unusual, the Post said.
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According to the White House, the surgery took place on Monday. He got out of the helicopter and climbed into an SUV, waving to reporters but declining to speak. Successful procedure, she is in good spirits.
Mrs. Trump has, at times, has been noticeably absent from her husband's side.
The White House has not offered any additional details on the first lady's condition.
Stephanie Grisham, the first lady's communications director, said in the statement that Trump would remain hospitalised through the week at Walter Reed National Military Medical Centre, in Maryland.
So, why does Melania's blood flow to her kidneys need to be blocked? "Thank you to all of the well-wishers!" Trump let everyone know via Twitter that it was a "Successful procedure, she is in good spirits". Mrs. Trump will likely be hospitalized for the rest of the week.
The Slovenian-born first lady last week rolled out an agenda for her White House work focused on helping children.