People whose kidneys fail in hospital are far more likely to die than doctors thought.
Only one in three patients is alive after three and a half years, according to study that has surprised researchers.
About 50,000 Australians and 11,000 New Zealanders a year suffer acute kidney failure, which usually occurs as a complication in seriously ill people who are already in hospital.
The condition is also known as kidney attack and is referred to as acute kidney injury in a PLOS Medicine journal article about the study.
The findings contradict a belief that survival is good for people who survive the first 90 days.
It was previously thought the concern was long-term kidney function, said research leader Associate Professor Martin Gallagher from the George Institute for Global Health and the University of Sydney.
"However, our study shows the death rate continues to be high after discharge from hospital.
"This is a higher death rate than from high-risk conditions such as heart attack."
Most of the 1058 Australian and New Zealand patients in the study had been admitted to hospital with severe illnesses, often infections, before they suffered kidney failure.
Prof Gallagher emphasised that many of those who died were older people and the actual cause of death could be related to their original medical condition.
Kidney Health Australia's Dr Timothy Mathew said hospitals needed to focus on monitoring patients.
"Acute kidney injury is a really important event that needs to be treated with respect.
"It would be best for hospitals to avoid it in the first place by improving monitoring and having quick reaction to any complications that occur.
"We also urgently need more resources to help patients who suffer acute kidney attack."