The hospitalization comes as Melania Trump, 48, has taken a higher-profile role in the White House in recent weeks. "The fact that she's in the hospital for [the remainder of the] week says to me there's a little more to the story", he said.
The procedure was "long-planned", according to Vice President Mike Pence, who stood in for Trump at a Monday night event in Washington, DC, celebrating Israel's 70 years of independence.
The Slovenia-born wife of Donald Trump underwent an embolization procedure, said her communications director Stephanie Grisham. The President spoke with his wife that morning and visited her that evening for over an hour. Her office had confirmed that the First Lady's procedure was "successful and there were no complications", and that she was on her way to a complete recovery.
"Heading over to Walter Reed Medical Center to see our great First Lady, Melania".
They are not common but tend to occur in middle-aged women and can cause problematic bleeding if they become large enough, said Dr Keith Kowalczyk of MedStar Georgetown University Hospital.
Embolization is most frequently used to cut off the flow of blood to a tumor or growth. Doctors do that with an embolisation - snaking a catheter into the blood vessels of the kidney to find the right one and block it.
The Trumps and their marriage have been under scrutiny in recent months after revelations that a porn actress was paid $130,000 in hush money to keep quiet about claims she had sex with Trump in 2006.
Last week, Trump gave a speech in the Rose Garden to announce a new campaign that she's calling "Be Best".