Acute kidney injury: An under-recognized complication of seasonal flu

The risk of developing acute kidney injury (AKI) is significantly higher in critically ill patients with influenza A than those with COVID-19, a study by researchers at the University of Hong Kong (HKU) has found.

The retrospective cohort study found that patients with COVID-19 had a 49 percent lower risk (adjusted odds ratio [aOR], 0.51; 95 percent confidence interval [CI], 0.42–0.61; p<0.0001) of AKI than those with COVID-19. Patients in the COVID-19 group also had a 43 percent lower risk (OR, 0.57; 95 percent CI, 0.45–0.72; p<0.0001) of developing severe (stage 3) AKI and a 48 percent (OR, 0.52; 95 percent CI, 0.40–0.67; p<0.0001) lower likelihood of requiring acute dialysis (prolonged AKI). [eClinicalMedicine 2024;70:102535]

The results were obtained from analysis of Hong Kong Hospital Authority’s electronic health record data of 4,328 patients (COVID-19, 64.4 percent; influenza A, 35.6 percent) who were admitted to intensive care units (ICUs) of 15 public hospitals in Hong Kong between January 2013 and April 2023. A total of 1,053 patients (37.8 percent) with COVID-19 and 828 patients (53.7 percent) with influenza A developed AKI of any stage during ICU stay.

 “These findings are in stark contrast to earlier reports, which suggested a higher risk of AKI and more severe renal impairment among COVID-19 patients,” said Dr Desmond Yap of the Department of Medicine, HKU, who led the research.

AKI is a common complication in critically ill patients and is a well-recognized sequelae in patients with respiratory infections caused by coronaviruses or seasonal influenza viruses. COVID-19 can cause AKI via direct virological invasion of renal cells and endothelial cell dysfunction, or via indirect mechanisms such as immune-mediated injuries. Influenza virus can cause various glomerular diseases, tubulointerstitial pathologies, as well as sepsis in critically ill patients, thereby leading to AKI.

The research team provided a few plausible explanations for the higher risk of AKI in influenza A patients. Firstly, the influenza virus could be more virulent or damaging to the kidneys than SARS-CoV-2. Secondly, and possibly more importantly, the significantly higher COVID-19 vaccination rates among the local population during the pandemic may have provided some protection against the development of kidney complications.

“Population statistics show that the local COVID-19 vaccination rate was over 70 percent for adults aged 20–59 years, and over 60 percent for adults aged 60–69 years. In contrast, the annual influenza vaccination rate was only 10–20 percent for persons aged 50–64, years and less than 50 percent for those aged 65 years or above,” the researchers noted. [https://www.chp.gov.hk/en/features/102226.html#] “It remains to be investigated whether the higher vaccination uptake during the COVID-19 pandemic moderated a lower risk of systemic organ injury.”

“Whether this under-recognized complication [ie, AKI] of seasonal influenza could be modified by a higher uptake of seasonal influenza vaccination and antiviral therapy should be studied,” they added.

“This study highlights the need for continued vigilance and prevention of severe respiratory viral infections,” emphasized Yap. “Despite the lower risk of kidney complications in COVID-19 patients, the burden of concurrent organ failure complicating respiratory viral infections, such as the higher disease-attributable risk of AKI associated with influenza, should not be overlooked, and vaccination should be strongly advocated for all at-risk individuals.”