Two urologists who have no personal knowledge of Ms Trump's condition said that the most likely explanation for the embolisation procedure is a kind of non-cancerous kidney tumour called an angiomyolipoma.
Mrs. Trump, who has been gradually raising her profile as first lady, recently hosted her first state dinner and launched a public awareness campaign to help children. Vice President Mike Pence, however, said in a speech Monday night that the procedure was "long-planned".
US President Donald Trump on Tuesday said his wife Melania is "doing really well" following a successful kidney procedure and will leave hospital within days.
An embolization is a minimally invasive treatment that blocks one or more blood vessels or abnormal vascular channels.
Such tumors are usually found by accident, when doctors are taking images for another reason, he said.
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The tax that made it across the finish line is actually smaller than the original proposal the city was considering. Almost 600 employers - about 3 percent of all Seattle businesses - would pay the tax starting in 2019.
That could mean that doctors are checking for a lung disease associated with angiomyolipomas, he said.
Trump addressed concerned citizens on social media Tuesday morning, thanking people for their "love and support" after announcing earlier this week that the First Lady underwent an "embolization operation" to treat a "benign" condition.
The president visited her on Monday evening and tweeted that the procedure was "successful" and that his wife was in "good spirits".
Trump departed the White House on Marine One shortly after 4 p.m. and touched down at the military hospital in Bethesda, Md., roughly 10 minutes later.
White House deputy press secretary Lindsay Walters said Melania Trump is in "good spirits". Walter Reed medical center, they did a fantastic job, so thank you. Mrs. Trump is 48. The president sat in the front row as she spoke.
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