Stan Guy is still searching for the reason his mother died in 2007 after she was admitted to a Nova Scotia hospital for a lump on her arm.

At first, the cause of death was pinpointed by the doctor as a bacterial infection. Then an autopsy revealed it was a fungal infection.

Watch the fifth estate's special Rate My Hospital report on Friday at 9 p.m. (9:30 in Newfoundland).

Now, the cause of death is being investigated by the province’s chief medical examiner, Dr. Matthew Bowes, who expects "somewhat different conclusions" will be found.

The case examined as part of Rate My Hospital, a special investigation into Canada's hospitals by CBC's the fifth estate, illustrates a broader issue surrounding the documenting of cause of death — and what it means for patients across the country.

Without accurately knowing what is killing Canadians, it is hard to prevent future deaths, Bowes warns.

"I tell my students … if you want to avoid death you should study why other people die. You know, it really is that simple. This isn’t rocket science," Dr. Bowes told the fifth estate co-host Linden MacIntyre.

An estimated 20 to 50 per cent of death certificates are incorrect, the pathologist said.

"I don’t have much confidence in the cause of death statements as a good measure of what is killing Canadians," Bowes added. "I think that you have to conclude that anything that is based upon a statement of the cause of death is probably flawed."

'I lost it at that point'

Patricia Guy, 71, of North Sydney, N.S., went to the Cape Breton Regional Hospital on July 23, 2007, for a swelling on her arm. Her son was worried about the lump, even though she was not.

"I felt relieved when I brought her to the hospital," said Stan. "We sort of left it in their hands like most people do when they bring someone to the hospital. You expect them to do the right thing."

Patricia had beaten leukemia and was dealing with a minor heart problem, but Stan says his mother was a "self-sufficient and a very strong-headed person" living on her own.

Three days after she was admitted to hospital, Patricia’s condition suddenly worsened. Stan began asking questions about what was going on, who was treating his mother and what her treatment was. He was then told that the physician treating his mother at the time was on vacation.

"He had never seen her," said Stan. "I lost it at that point and immediately, almost immediately, they took her to ICU."

The next morning, Patricia fell into a coma. Days later, she died. The hospital’s official summary of death said she died of sepsis, a condition where the body’s reaction to an infection can damage tissue and organs.

Search for truth

Stan demanded his mother’s medical charts and records, and spent months going through them, seeking medical advice on what it all meant.

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Stan Guy spent months poring over his mother's medical records after she died in 2007. (Submitted by Stan Guy)

Her death launched the Halifax web developer into the convoluted world of hospital record-keeping, and into a controversial issue on the minds of Canadian hospital administrators some have dubbed "care after death" — accountability after death for the quality of care received while alive.

In March 2009, Stan filed a formal complaint with the Nova Scotia College of Physicians and Surgeons naming five doctors.

The college reprimanded one doctor, questioning his "clinical acumen" and "record keeping," and issued a caution to another doctor.

Among the issues Stan raised with the college was a note he found buried in his mother’s medical file. A doctor had erroneously prescribed medication that might have made her illness worse.

"I was never told that. I had no idea that she was given that incorrectly," Stan told the fifth estate's Linden MacIntyre. "There's nothing about it in the autopsy either."

Unsatisfied with the college’s investigation, Stan eventually went to the Nova Scotia chief medical examiner in the summer of 2011.

Slip through the cracks

Before the chief medical examiner’s investigation into Patricia’s death even concluded, Bowes sent a letter to Deputy Health Minister Kevin McNamara saying the case had raised "potential systemic issues."

"I request that you review this lady’s care, with a view to improving health care delivery," Bowes wrote in the letter.

The pathologist believes that every death is an opportunity to learn how to make the health-care system better. Stan hopes that more can be learned about why his mother died – and what can be done to prevent other deaths.

"If my mom can slip through the cracks, and the mistakes that were made aren’t fixed, it’s going to happen to other people, other people’s moms and people that matter to them," he said.

To contact the Rate My Hospital team with tips or information related to the series, please email ratemyhospital@cbc.ca.