U.S. President Donald Trump said on Monday that he underwent an MRI during his most recent visit to Walter Reed National Military Medical Center, but he declined to provide details about the reason for the scan.

The comments marked the first time Trump, 79, has offered an explanation for his second medical exam this year. 

The October 10 visit, described by the White House as a routine yearly checkup, prompted questions about the president's health as it came just six months after he had an extensive physical examination.

“I did. I got an MRI. It was perfect,” Trump told reporters while flying to Tokyo.

But Trump, who is one of the oldest presidents in U.S. history, would not say why he received the scan, telling reporters traveling with him to “ask the doctors.”

The White House did not immediately respond to questions seeking more detail on the reason for the MRI.

The president said his doctors had offered reporters a “very conclusive” report of the exam, but the White House has not disclosed why Trump made a second visit to Walter Reed, a departure from the traditional presidential cadence of a single comprehensive exam per year.

"Trump remains in exceptional health, exhibiting strong cardiovascular, pulmonary, neurological, and physical performance," Trump's physician Sean Barbabella said in a memo released after the visit.

The doctor noted in the memo that the evaluation helped prepare for Trump’s upcoming overseas trips and included advanced imaging, lab testing and preventive health assessments.

A magnetic resonance imaging scan uses magnets and radio waves to create detailed images of the inside of the body. It can be used to monitor a range of conditions.

In July, the White House disclosed that Trump was experiencing swelling in his lower legs and bruising on his right hand, after photographs showed the president with swollen ankles and makeup covering the afflicted part of his hand.

In a letter released at the time, Barbabella said tests confirmed the leg issue was due to "chronic venous insufficiency," a benign and common condition, especially in people over 70 years old.

The doctor said the bruising on Trump's hand was consistent with minor soft tissue irritation from frequent handshaking and aspirin use, which Trump takes as part of a "standard cardiovascular prevention regimen."

Since then, the White House has played down concerns about Trump's health, without detailing how the leg issue is being treated.