Millions of COVID-19 patients may have an undiagnosed, potentially fatal acute kidney disease, according to a new study.

University of Queensland researchers say one in five virus patients admitted to hospital and two in five in intensive care develop acute kidney disease (AKI), a condition where the kidneys fail to filter waste from the blood.

University of Queensland PhD candidate and kidney specialist Dr Marina Wainstein says a new study indicates AKI rates in COVID-19 patients could be double that.

Doctors test for the disease by monitoring a patient's urination and creatinine levels in their blood, but Dr Wainstein says if a patient's creatinine levels rise before they're hospitalised they may not be diagnosed with AKI.

She says monitoring creatine levels reveals that the rate of AKI in COVID-19 patients could be double the official figures.

"We can miss the AKI diagnosis and fail to manage the patient appropriately in those early, critical days of hospitalisation," Dr Wainstein said in a statement.

"That was a pretty shocking finding."

She said the finding is important because the research also showed that COVID-19 patients with acute kidney disease had worse medical outcomes in hospital and were more likely to die than other virus patients.

Dr Wainstein said proper AKI diagnosis was vital as there are relatively simply treatments for the potentially fatal disease, such as increasing a patient's hydration level and stopping medications that can be toxic to kidneys.

UQ's Dr Sally Shrapnel, who supervised the study, said analysing the data was difficult as it was collected by hospital staff worker under "extremely onerous conditions" in a range of settings.

However, she said the study included data from countries where people had limited access to healthcare and were more likely to present to hospital when the disease was advanced.

Dr Shrapnel said she hopes the study will create more comprehensive AKI definition and improve testing of patients for the disease.

"Now we have the data showing a large gap in AKI diagnosis exists, it's time to test this definition in a clinical trial so we can identify all AKI patients early and hopefully prevent these awful outcomes," she said.