What is the impact of COVID-19 on the kidney, both in adults and children? That’s the question Erica Bjornstad, MD, and others have been studying since the pandemic started. Their recent paper, published in BMC Nephrology, provides the first data demonstrating the risk of acute kidney disease among the entire age range, from newborns to 99-year-olds. The findings, Bjornstad said, were surprising.
“We all know that the severity of COVID is worse the older you are, and we’re not disputing that,” she said. “But what we found is that risk of acute kidney injury, or AKI, does not go in a straight line.” Instead, it has a bimodal distribution, with the risk peaking in children between ages 10 and 15, decreasing until about 30, then continuing to rise in a more linear fashion. The study was based on the records of 6,874 patients hospitalized with the virus.
“Why does a 10-to-15-year-old have the same risk of acute kidney injury as a 65-year-old, but a higher risk than a 35-year-old?” she asked. The higher risk in children held even after accounting for those with chronic medical conditions.
Bjornstad and her coauthors hypothesize that it may have to do with how the virus attacks the endothelium, the lining of the blood vessels, although that doesn’t explain the effect in adolescents. “Maybe there are hormonal changes happening during puberty that make them more susceptible to kidney injury risk. We really don’t know why. All we can say is that the epidemiological data shows it exists, and we need to study that further.”
The study also found a high rate of AKI in non-critically ill patients—those who were not in the ICU—something that previously had not been reported. However, the children who do get AKI with COVID are generally very sick and hospitalized, she said. “I haven’t seen children come to my attention from the outpatient side who got COVID, were never hospitalized, and now have kidney problems,” although there have been very rare cases elsewhere.
The findings are important for clinicians who treat children, adolescents and younger adults, she said. “For the most part, COVID is benign in kids. But we have to have a higher index of suspicion for acute kidney injury in this population.”
“If something doesn’t feel right, or the child isn’t acting right, even after very mild cold-like symptoms, we should run some blood tests to check for the injury resulting from the endothelial attack,” she said. The concern about AKI comes because it increases the risk for high blood pressure and chronic kidney disease.
Bjornstad and other nephrologists at Children’s also published a review article in Pediatric Nephrology last year highlighting all that was known to date on the impact of COVID on the kidney in pediatric patients. The paper included several clinical pearls for clinicians. For instance, early in the pandemic there was concern that anyone with COVID taking an ACE inhibitor should stop. “But there’s really good data that if you have a child with COVID on an ACE inhibitor they should not stop it,” she said.
Their papers and others on the topic generally end with the same call for more research. “There are some immune dysregulation syndromes that affect the glomerular part of the kidney that is presumably triggered by COVID,” Bjornstad said. “But we need to keep looking to see if there are other mechanisms.”