“Usually a one-night stay does more than enough,” Dr. Hong said, “and the next day the patient is discharged with oral analgesics or painkillers. It’s sort of unusual to keep someone longer.”

Dr. Hong said patients typically went in for the procedure after experiencing symptoms like blood in the urine or back or stomach pain. Once patients were discharged, Dr. Hong said, he normally would not see them for another month.

At this point in Mrs. Trump’s recovery, specialists say it is hard to know why she would remain in the hospital for the better part of a week. It is possible that a patient could stay longer after an embolization procedure if there were underlying medical conditions, or if an infection, pain or discomfort developed afterward, Dr. Joseph A. Vassalotti, the chief medical officer at the National Kidney Foundation, said in an interview.

“I would say that I hope that when she is ready she’ll come out and tell the American public about what condition she has and what happened,” Dr. Vassalotti said.

Given Mrs. Trump’s desire to keep her private life private, that is probably unlikely. The first lady’s team kept her procedure, and details about when she actually entered Walter Reed, under lockdown. White House aides who were near Mrs. Trump wore blue scrubs in the hours immediately after the procedure, according to a person who saw several of the first lady’s aides at Walter Reed.

Wearing scrubs, Dr. Hong said, would be unnecessary for people interacting with a patient who had undergone an embolization procedure.

The president visited Mrs. Trump for the first three days of her stay at Walter Reed, stopping on Wednesday for a photo op with wounded soldiers. But on Thursday, the White House offered no further details on Mrs. Trump’s health, and Mr. Trump did not visit. According to a White House official, who spoke on the condition of anonymity to detail the president’s travel plans, a weekend trip to Camp David had been canceled and Mr. Trump had plans to stay in Washington.

Since moving to Washington with the couple’s 12-year-old son, Barron, last year, Mrs. Trump has made it clear that his privacy is of paramount importance, and hers nearly as important. It is a directive her small team of 10 aides has taken seriously, even as Mrs. Trump’s popularity has surged amid a series of high-profile appearances, including a state dinner with France and the launch of Be Best, her official platform that focuses on teaching kindness to children.