Mayor Thomas M. Menino suffered another setback and will remain hospitalized indefinitely as doctors try to determine what caused a fresh surge of pain in his ailing back.
Speaking Tuesday at a press conference, two of Menino's physicians said they could not give any estimate when the mayor might be released from Brigham and Women's Hospital, where he was admitted almost three weeks ago.
"He was getting better, then recently [he experienced] more pain and that has been responsible for the holdup," Dr. Dale Adler told a throng reporters. "All the other problems are taken care of. Now the focus is why his back is hurting him more. There are a plethora of theories, and that's what we're going to work on."
Menino, 69, was initially diagnosed with a viral infection and a blood clot. While hospitalized, he sustained a compression fracture in one of the vertebra of his spine. He made progress on all fronts, doctors said, until the new surge of pain in his back.
The five-term mayor has not set foot in City Hall for a month. He left Oct. 14 for what was supposed to be a two-week trip to Italy with his wife for their 46th anniversary. Feeling ill, Menino cut the trip short, returned to Boston, and was admitted to the hospital Oct. 26.
Over the past few weeks, Menino has continued to run the city from his hospital bed, according to his spokeswoman, Dot Joyce.
At least twice a day, aides shuttle documents from City Hall to the hospital, Joyce said, bringing Menino briefing memos to read, labor contracts to sign, and a City Council redistricting ordinance to approve.
While Menino was in Italy, City Council President Stephen J. Murphy took over a few of his duties, signing documents so money could be disbursed to pay the city's bills.
The temporary transfer of power is outlined in the city charter, which stipulates that the council president becomes acting mayor when Boston's chief executive is absent from the city.
Since Menino's return to Boston, the mayor has been in full control.
"He's been running the city," Murphy said Tuesday. "He's got a good team. When I talked to him last week, he sounded like he had his fastball."
Joyce said Tuesday that Menino had no intention of transferring power to Murphy while he remained hospitalized.
Menino may be engaged, but his communication to city employees has been limited to a handful of top aides. Over the past month, that has marked a stark change at City Hall. In his nearly two decades as mayor, Menino has earned a reputation as a micromanager who will often surprise midlevel city employees with a phone call or summons to his office on the fifth floor.
The prolonged hospitalization also comes at a difficult political moment for Menino, who must decide by the spring whether he will run for a sixth term.
Menino has been aggressively raising money and by all accounts appeared to be gearing up for another campaign. However, this string of illnesses may shatter Menino's air of inevitability and encourage would-be challengers to prepare.
At Tuesday's press conference, Joyce declined to address the political speculation or release a recent photograph of the mayor. But she did make a strong plug for her boss.
"The mayor is a tough cookie," Joyce said. "No one should underestimate him."
On Tuesday, as doctors took questions from reporters, they revealed a few new details about Menino's health. The blood clot that he developed in one leg traveled to his lungs before it dissipated, doctors said. The clot probably developed on the long flight to Europe.
Adler and the other physician, Dr. Charles Morris, also rejected the suggestion that Menino may have an underlying disorder such as cancer that has made him more fragile.
Despite taking painkillers and other medication, Menino remains lucid, his doctors said.
"He is completely clear [and] able to make decisions appropriately," Morris said. "He is engaged with us, his team, the staff, and with everybody he needs to be."
The most significant question was why Menino has remained in the hospital for so long. Doctors acknowledged Tuesday that a few days ago, Menino was almost well enough to be released. They suggested that if he had been another patient and not the mayor of Boston he may have been discharged. Instead, he had remained in the hospital for physical therapy.
"We were trying to figure out what was the best way to get him some rehabilitation," Adler said. "We decided maybe the best way would be for him to stay right here where we could watch him and supervise.''
But then pain flared in Menino's back. He was outfitted with a support brace when he walked, doctors said, and he has therapy twice a day. But there is no longer a question about whether he needs to be hospitalized.
"Now he needs to be in the hospital" for his back, Adler said.
Andrew Ryan can be reached at firstname.lastname@example.org Follow him on Twitter @globeandrewryan.