It could be as long as a week before Toronto Mayor Rob Ford has a diagnosis for the tumour in his abdomen and a course of treatment is determined, news that continues to leave his political future in question.

Dr. Zane Cohen, a colorectal surgeon, and director of the Zane Cohen Centre for Digestive Diseases at Toronto's Mount Sinai Hospital said Mr. Ford has a mass in his lower abdomen and will continue to undergo tests Friday.

"He is resting comfortably," Dr. Cohen told reporters at a press conference Thursday evening. "He has some pain. We are giving him some pain medication for that. He is surrounding by family members."

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Dr. Cohen refused to speculate about the nature of the problem or treatment until results from a biopsy taken Thursday are in. Mr. Ford also underwent a CT scan of his chest and abdomen and an ultrasound of his chest.

He will have a MRI Friday.

"We are still in a holding pattern," Dr. Cohen said.

Mr. Ford was transferred to Mt. Sinai Hospital in downtown Toronto Thursday afternoon for "follow-up investigation and subsequent treatment" according to a press release issued by that hospital. Mr. Ford was admitted to a west end hospital Wednesday where initial tests showed a tumour in his lower left abdomen.

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The mayor left via the back door of the hospital in the early afternoon, according to a woman who said she saw it from a sixth-floor window.

Jaklin Gulpashin, who was at the hospital visiting her mother, said she saw nurses rushing to a window and went to see what was catching their attention. From that vantage point, she said, she could see Mr. Ford on a stretcher being loaded into an ambulance.

"He was looking around," she said. "He was okay. He was good. He looked happy."

While Mr. Ford's physical health was top of mind Thursday, his political fate also hangs in the balance, with less than 24 hours until the deadline to decide if his name will remain on the ballot for the October 27 election. Friday also is the last day to enter the race and all eyes are on the mayor's brother and campaign manager Doug Ford, who is declining to talk about the possibility that he will step in if his brother's health prevents him from continuing.

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"I'll speak to you folks in the next couple of days," a grim-faced Doug Ford told reporters Wednesday night.

His main rivals - John Tory, who is leading in recent opinion polls and Olivia Chow – sent prayers to Mr. Ford during an interfaith breakfast Thursday morning. Ms. Chow postponed a campaign endorsement event Thursday, but she and Mr. Tory will go head-to-head for the first time at a debate Friday morning and again on Sunday.

"We want to collectively wish him strength in the days ahead. Our prayers are with him and his family because we want him to be back out here as soon as he can," Ms. Chow  said.

"I join Olivia in saying a prayer," Mr. Tory said. "Our thoughts go out to our missing colleague who's not here this morning and who is grappling with health issues ... We would want him to be back at these debating tables with us."

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At City Hall, the mayor's spokesman Amin Massoudi said Thursday morning that work in the office was continuing. "We are carrying on business as usual. We're dealing with constituents who are calling us and helping Toronto residents, and doing the work of the mayor's office," he said.

Mr. Massoudi reiterated a request for privacy for the Ford family, but added that the office has seen an outpouring of support since the news broke. "There have been a lot of calls coming in – a lot of support. We feel grateful for that."

Mr. Ford was admitted Wednesday to a west-end hospital near his Etobicoke home complaining of abdominal pain. News of the tumour came in a press release issued early Wednesday evening.

Dr. Rueben Devlin, CEO of Humber River Hospital, told reporters Mr. Ford came to the hospital earlier in the day, after experiencing "unbearable" pain in the lower left quadrant of his abdomen.

"The tumour is in his abdomen, that's our working diagnosis based on CT scan," Dr. Devlin said at a hastily called news conference Wednesday night.

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A stoic Doug Ford, the mayor's brother and campaign manager, stood beside the doctor for most of the news conference, held in a small room at the hospital.

"It saddens me that I have to be here today," Doug Ford told reporters. "Rob's in good spirits, and I just want to thank the well-wishers."

The shocking news comes the same day as the race for mayor narrowed to three front-runners – Mr. Tory, Ms. Chow and Mr. Ford – with fourth placed David Soknacki withdrawing from the race.

Mr. Ford has captured international attention with his battle with addiction after the discovery of a videotape that appeared to show him smoking crack last year. He is still the subject of an ongoing police investigation. His bid to recapture the mayoralty of Canada's largest city is being closely watched.

Mr. Ford has tried to put controversy behind him since he returned this summer from a two-month stint in rehab, even as the latest polls showed Mr. Tory as the frontrunner.

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Since returning from rehab in late June, Mr. Ford has fended off frequent questions about his health by saying he's adopted a new, healthy lifestyle. Last month, he told reporters "I'm as sober as a judge. We're working out, we're doing great. I'm feeling healthy."

Doug Ford was asked if he would enter the race if his brother is unable to run, but would not answer that question. "Give our family a day or so," he said, his voice breaking with emotion.

The mayor's last public appearance was at a debate Tuesday night. By Wednesday afternoon, news began to circulate that he had withdrawn from several events this week, leading to a flurry of speculation about his whereabouts.

Mr. Ford spent two months in rehab this spring, to deal with alcohol and drug addictions and the last-minute cancellations led to speculation about his whereabouts.

A statement from the hospital said Rob Ford had experienced similar pain over the past three months, but that it became worse in the past 24 hours.

"It was just today, just today," Doug Ford said when asked when the pain started.

Doug Ford said that the pair had breakfast together Wednesday morning, where he mentioned pain in his abdomen. After consulting with a doctor, the mayor attended the hospital's emergency room, he said.

Doug Ford left with the mayor's chief of staff and press secretary before the news conference ended.

Humber Valley's Dr. Devlin is a former president of the Ontario Progressive Conservative party, and in 2008, was part of a movement to try to remove John Tory as leader.

Rob Ford attended several campaign events Tuesday, including a photo-op with former heavyweight champion Mike Tyson at City Hall, and a debate in North York in the evening.

But on Wednesday, he was nowhere to be seen at City Hall, with his staff declining to comment when reporters asked about the mayor's whereabouts.

This is the second time in recent months the mayor has received medical treatment in hospital. In July, he was spotted at Toronto Western Hospital, after complaining of a foot injury.

At the time, Doug Ford said his brother would need to undergo foot surgery the next week in order to address the injury, which he later said would be pushed back.

Mr. Ford was also treated for a tumour in his appendix in 2009.