The Effects of Covid-19 in Children Extend to the Kidneys
Hospitalized children with the inflammatory syndrome linked to Covid-19 have increased risk for acute kidney injury
For a while, early on in the pandemic, the world sighed with some relief at the apparent low risk the SARS-CoV-2 virus held for children. That sigh turned to an intake of breath with reports of a new syndrome emerging in children, apparently associated with the virus and often coming on well after any apparent infection. It wasn’t the first 180-degree turn Covid-19 data had taken, and it wasn’t the last.
The syndrome, called multisystem inflammatory syndrome in children, or MIS-C, involved symptoms hinted at in its name: inflammation across many systems in children. If caught and treated soon enough, MIS-C seemed to end with recovery for most.
One pair of organs that seemed to be spared from MIS-C was the kidneys. Then in July 2020, reports emerged of high rates of acute kidney injury in adults who’d been hospitalized with Covid-19, with an ominous prognosis.
In less than a week after that report appeared, researchers writing in Nature Pediatric Research walked through a review of the different body systems that MIS-C seemed to affect. In contrast to what had just been published a few days earlier, they wrote that evidence for acute kidney injury in adults was limited and that no information was available on kidney effects in children.
That has been the way with Covid-19 since it first found human hosts: What the evidence has indicated one week could very well change the next as new information came in. We thought children were largely safe, then MIS-C cropped up. We thought kidneys might largely escape injury in adults, and within a week, the information had changed. The kidney story in children is no different.
By November, other researchers publishing in Nature Pediatric Research noted that kidney injury was an “evolving area” in Covid-19, expressing a concern that the actual rate of acute kidney injury was potentially higher than anyone had originally thought in adults. They also noted at least one study finding it in 18% of children who had severe or critical Covid-19 and a small U.K. study reporting acute kidney injury in some patients with MIS-C. From there, the creep of information on kidney injury in children who had Covid-19 began to pile up.
Since fall, more evidence has emerged of a link between kidney injury and MIS-C. In March, just days short of the anniversary of the pandemic declaration, a study published in Kidney International showed that 18.2% of children with Covid-associated MIS-C develop acute kidney injury, compared with 8.2% of children who had Covid-19 without the inflammatory syndrome. (Symptoms of the inflammatory syndrome include fever, gastrointestinal problems, and rash.)
Children whose kidneys were compromised had a longer length of hospital stay in this New York-based study, but the kidney injury resolved in all but two before discharge, and none of the children with MIS-C died. Acute kidney injury was more common among Black children. Unlike some previous studies, the authors found no association between the inflammatory syndrome and obesity.
These findings so far suggest that with Covid-19, children develop kidney injury less often than adults but still have increased risk for it. Children who have MIS-C — the inflammatory syndrome associated with Covid-19 — have higher risk compared to those with Covid-19 without the syndrome. But as we have learned again and again with Covid, those conclusions could change.