Researchers, including one of Indian-origin, have found that there is much higher risk of mortality faced by Covid-19 patients in intensive care, who have chronic kidney disease (CKD), or those who develop new (acute) kidney injury (AKI).
CKD is a type of kidney disease in which kidney function declines over a period of months to years, and is more common in older people.
AKI is an abrupt loss of kidney function that takes place over seven days or less and can have several causes, including the damage and inflammation caused by the Covid-19 virus itself.
"To the best of our knowledge, this is the first comprehensive analysis of outcomes in critically unwell Covid-19 patients in the UK with kidney failure, particularly in patients with pre-existing chronic kidney disease," said study author Sanooj Soni from Imperial College London in the UK.
For the study, published in the journal Anaesthesia, the research team examined the association between AKI and CKD with clinical outcomes in 372 patients with Covid-19 admitted to four regional intensive care units (ICUs) in the UK.
The average age of the patients was around 60 years, and 72 per cent of them were male.
A total of 216 (58 per cent) patients had some form of kidney impairment (45 per cent developed AKI during their ICU stay, while 13 per cent had pre-existing CKD), while 42 per cent had no CKD or AKI.
The patients who developed AKI had no history of serious kidney disease before their ICU admission, suggesting that the AKI was directly related to their Covid-19 infection.
The authors found that patients with no kidney injury or disease had a mortality of 21 per cent.
Those with new-onset AKI caused by the Covid-19 virus had a mortality of 48 per cent, whilst for those with pre-existing CKD (Stages 1-4) mortality was 50 per cent.
In those patients with end-stage kidney failure (CKD stage 5), where they already required regular out-patient dialysis, mortality was 47 per cent.
Mortality was greatest in those patients with kidney transplants, with six out of seven patients (86 per cent) dying, highlighting that these patients are an extremely vulnerable group.
The investigators also examined the rates of renal replacement therapy, a form of hospital dialysis, due to Covid-19 in these ICU patients with kidney injury.
Out of 216 patients with any form of kidney impairment, 56 per cent of patients requiring renal replacement therapy, the researchers said.
The authors noted that mortality in patients with end-stage kidney failure and on dialysis, who normally have worse outcomes in many other diseases, was similar to that in patients with less severe kidney disease and Covid-19 associated AKI.
This finding may suggest that such patients benefit equally from ICU admission and thus the threshold for admission should be calibrated accordingly in any future Covid-19 surge.
"Our data demonstrate that kidney disease and failure in critically ill patients with Covid-19 are common, and associated with high mortality," the authors noted.