President Trump visited his wife in the hospital again this afternoon in Bethesda, Maryland, as the first lady continued to recover from a surgery to treat a benign kidney condition.

First lady Melania Trump is 'doing really well,' the president wrote online Tuesday morning following up on a visit to her in the hospital the day before.

Deputy White House press secretary Lindsay Walters said in an update after he returned, 'As her office has stated, the First Lady remains in good spirits.'

President Trump is visiting his wife in the hospital again this afternoon in Bethesda, Maryland, as the first lady continues to recover from a surgery to treat a benign kidney condition

President Trump on Tuesday thanked the 'incredible doctors' who operated Monday on the first lady at Walter Reed Medical Center

Trump was speaking at an annual memorial service for law enforcement officers who died in the line of duty when he made the remarks on Tuesday morning before his second visit to Bethesda

President Trump publicly thanked the first lady's medical team at the beginning of a speech to law enforcement officers, during an annual memorial service to honor fallen heroes later in the morning on Capitol Hill.

'Melania is in the hospital doing really well. She's watching us right now,' Trump said. 'And I want to thank the incredible doctors. Walter Reed Medical Center. They did a fantastic job. So thank you. She sends her love.'

This afternoon the president left the White House just after 4 o'clock on Marine One, the helicopter reserved for use by U.S. presidents, and flew to Walter Reed National Military Medical Center in suburban Bethesda, Maryland to see his wife.

He was back at the White House less than two hours later, returning to the Oval Office shortly before 6pm.

He ignored reporters' shouted questions about an explosive news report that North Korea has threatened to call off a planned June 12 nuclear disarmament summit on his way to and from Marine One.

Trump took the same chopper to Walter Reed late afternoon Monday and visited his wife hours after she underwent her kidney procedure.

He said Tuesday that she will be leaving the hospital in two or three days – a time frame consistent with what her office said Monday when it announced that she would remain under observation through the week.

'Our great First Lady is doing really well. Will be leaving hospital in 2 or 3 days. Thank you for so much love and support!' Trump wrote on Twitter.

President Trump tweeted Tuesday that the first lady is 'doing really well' following a medical procedure to treat kidney problems at Walter Reed National Medical Center

First Lady Melania Trump underwent surgery at Walter Reed National Military Medical Center in a kidney procedure, her office announced Monday

He had earlier used social media to say she was in 'good spirits' after a 'successful procedure.'

Melania underwent an embolization procedure, likely to remove a cyst from her kidney. Her office said it was benign, or non-cancerous.

The first lady's office announced the first lady had the procedure Monday. President Trump was at the White House Monday when her surgery occurred

He spent about an hour at the hospital before returning to the White House via motorcade while a powerful thunderstorm approached.

Trump tweeted about the visit while he was en route. 'Heading over to Walter Reed Medical Center to see our great First Lady, Melania. Successful procedure, she is in good spirits. Thank you to all of the well-wishers!'

Before that, though, Trump went on a Twitter tirade about leakers that had drawn criticism from all ends of the political spectrum. He tweeted about a White House hunt for leakers before he expressed concern for his wife.

Tuesday Trump avoided making the same mistake, saying in his first tweet of the morning: 'Our great First Lady is doing really well. Will be leaving hospital in 2 or 3 days. Thank you for so much love and support!'

Minutes later he tweeted about trade negotiations with China. Roughly 30 minutes later he was back on the leakers, whom he had called cowards and traitors the day before.

Past medical procedures by first ladies while in the White House Nancy Reagan: Got a mastectomy in 1987 as treatment for breast cancer Rosalynn Carter: Surgery to remove a lump from her breast in 1977. The tumor was benign. Betty Ford: Had a mastectomy in 1974 Source: CNN Advertisement

The first lady's office has provided no update on her condition beyond its original statement.

The president didn't respond to questions as he approached the presidential helicopter en route to the military hospital in Bethesda, Maryland, on Monday, either.

Under a procedure like the one that Melania underwent, doctors block a flood vessel in order to stop blood flow to a specific area and stop a patient from bleeding.

'This morning, First Lady Melania Trump underwent an embolization procedure to treat a benign kidney condition,' according to a statement from her communications director, Stephanie Grisham.

Trump tweeted about his visit to see the first lady en route

'The procedure was successful and there were no complications. Mrs. Trump is at Walter Reed National Military Medical Center and will likely remain there for the duration of the week,' her communications director Stephanie Grisham said in the statement.

'The First Lady looks forward to a full recovery so she can continue her work on behalf of children everywhere,' she said, in reference to her recently launched campaign.

The first lady is 48 years old and has been married to President Trump since 2006.

A statement was released only after her surgery was completed, and it took Trump hours after that to make a comment of his own.

ABC News reported that Trump spoke to his wife before the procedure and talked to her doctor afterward.

Melania Trump unveiled her campaign to try to help children last week

First lady Melania Trump (L) arrives in the East Room to deliver remarks during the White House Opioid Summit March 1, 2018 in Washington, DC

First lady Melania Trump and her son Barron Trump look at the Wisconsin-grown Christmas Tree at the North Portico as it makes its way the Blue Room for display at the White House in Washington, DC on Monday, Nov. 20, 2017

Walter Reed National Military Medical Center is seen after US President Donald Trump arrived for his annual physical in Bethesda, Maryland, January 12, 2018

Trump on Tuesday lifted off from the White House's South Lawn in the afternoon to see his wife

EXPLAINED: THE KIDNEY EMBOLIZATION SURGERY MELANIA TRUMP UNDERWENT by Natalie Rahhal, health correspondent, and Mia de Graaf, health editor A kidney embolization is a simple procedure done to intentionally block off a blood vessel in the kidney. 'Embolization is a minimally invasive procedure to stop blood flow to parts of an organ (in this case kidney),' Dr Jamin Brahmbhatt, a urologist at Orlando Health, explains. 'It can be used to treat malignant and benign lesions.' WHY IS IT DONE? An embolization is often used as a first-line treatment for any kind of gastrointestinal bleeding, but it can also be preventative. It can be performed on any organ that has a growth or blood vessel clump. There are typically two scenarios for performing a kidney embolization: Preventative: to cut off a tumor's blood supply and shrink, or control a cyst it before it can rupture Emergency: to stem bleeding of a ruptured cyst on the organ There are three things on which kidney embolizations are peformed: To shrink a cancerous tumor by cutting off the blood supply To shrink a benign cyst (i.e. a angiomyolipoma) by cutting the blood supply To fix an arterial vessel malformation (a clump of blood vessels) Angiomyolipomas are benign growths. They disproportionately affect women. Eighty percent of them are spontaneous, while 20 percent of them are genetic Melania Trump's operation was reportedly for a 'benign' kidney condition. Dr Brahmbhatt believes it was like an angiomyolipoma. These growths disproportionately affect women (four times more than men), and 80 percent of them are spontaneous (compared to 20 percent which are genetic). Surgery is only recommended if it grows too big. 'If they're under four centimeters, we just monitor it,' Dr Brahmbhatt explained. 'But if it goes over four centimeters, the risk of it rupturing goes up way high, so that's when we suggest treatment.' HOW IS IT DONE? Typically, a patient is given sedation and the entire procedure is done through an X-ray view. The doctor makes a small incision near the groin, and guides very long, skinny tube, called a catheter, through a blood vessel toward the kidney. There, an 'agent' or chemical that causes the blood to clot is injected, cutting off the flow of blood to through that particular vessel. The entire procedure commonly takes up to three hours and hospital stays afterwards vary. HOW IS THE RECOVERY? 'After embolization patients often have nausea, vomiting, fever, and pain that could last a few days,' Dr Brahmbhatt said. 'These procedures are fairly low risk but still require close follow-up.' Embolizations are minor operations, with relatively low risks of complications or side effects. In very rare cases, patients may have a bad reaction to the dye used in the procedure. More commonly, some have discomfort or minor bleeding after an embolization, and as such they are monitored over night. Some people develop fever, weakness and nausea, a temporary condition called 'post-embolization syndrome,' that usually subsides within a few days. Advertisement

According to CNN, she is the first first lady to have such a serious operation since Nancy Reagan had a mastectomy in 1987 while her husband was in office.

Dr. Sanjay Gupta spoke about the procedure on CNN as the news first broke. He had been on air already to talk about former Senate Majority Leader Harry Reid's treatment for pancreatic cancer at Johns Hopkins University on Monday.

'[It's] unclear exactly what she had done. An embolization procedure is typically done for cancer, although it's very clear in this statement that this was a benign condition,' said Gupta.

'That's how they've framed it. So it doesn't sound like it's any type of cancer,' he added.

'Sometimes thyroids, or cysts, or something like that, can be treated as well [through embolization],' Gupta said.

The statement from Trump's office did not describe what exactly was being treated on her kidney, whether a cyst or some kind of non-cancerous tumor.

First Lady, Nancy and U.S. President Ronald Reagan, look at flowers received from well-wishers on October 19th, 1987 at the Bethesda Naval Hospital

President and Mrs. Ford return to the President's Suite at the Bethesda Naval Hospital, following the First Lady's breast cancer surgery

The official White House statement did not spell out whether she underwent surgery or merely the procedure, which relies on catheters used to try to stem blood flow.

The news comes just a week after the first lady took on a high-profile role by announcing the initiatives she would carry on in her post. She said she wanted to focus on children's health, opioid abuse, and preventing bullying online.

A kidney embolization is a simple procedure done to intentionally block off a blood vessel in the kidney.

Under an embolization, typically, a patient is given local anesthesia and the entire procedure is done through an X-ray view.

The surgeon makes a small incision near the groin, and guides very long, skinny tube, called a catheter, through a blood vessel toward the kidney.

There, an 'agent' or chemical that causes the blood to clot is injected, cutting off the flow of blood to through that particular vessel.

Kidney embolizations are generally performed when a patient is having kidney bleeding either from trauma, a tumor, or another medical condition.

Melania Trump's operation was reportedly for a 'benign' kidney condition.

The entire procedure takes up to three hours and hospital stays afterwards vary.