Since the beginning of the pandemic, doctors have found that people who get very sick with Covid-19 often suffer from kidney problems and not just the lung dysfunction that is the hallmark of the disease.
Now, a large study suggests that kidney problems can persist for months after patients have recovered from the initial infection and can lead to serious lifelong kidney function problems in some patients.
The study, published Wednesday in the Journal of the American Society of Nephrology, found that the sicker Covid patients were initially more likely to suffer from permanent kidney damage.
But people with less severe initial infections could also be susceptible.
“You are seeing a higher risk across the board for a number of major kidney-related events,” said Dr. F. Perry Wilson, a nephrologist and associate professor of medicine at Yale who was not involved in the study. “And what particularly struck me was that these persisted.”
The kidneys play an important role in the body by removing toxins and excess fluids from the blood, maintaining healthy blood pressure, and maintaining a balance of electrolytes and other important substances. When the kidneys don’t work properly or efficiently, fluid builds up, causing swelling, high blood pressure, weakened bones, and other problems.
The heart, lungs, central nervous system, and immune system can be affected. End-stage kidney disease may require dialysis or an organ transplant. The condition can be fatal.
The new study, based on patient records in the Department of Veterans Affairs health system, analyzed data from 89,216 people who tested positive for the coronavirus between March 1, 2020 and March 15, 2021, as well as data from 1,637,467 people who no Covid patients.
Between one and six months after infection, Covid survivors were 35 percent more likely than non-Covid patients to experience kidney damage or a significant decline in kidney function, said Dr. Ziyad Al-Aly, director of research and development for the VA St. Louis Health Care System and lead author on the study.
“People who survived the first 30 days of Covid are at risk of developing kidney disease,” said Dr. Al-Aly, a nephrologist.
Since many people with impaired kidney function do not experience pain or other symptoms, “it is really important that people realize that there is a risk and that doctors who care for post-Covid patients are really paying attention to kidney function and disease”, he said.
The two patient groups in the study differed in that members of one group were all infected with Covid, and members of the other group may have had a variety of other health conditions. Experts warned that there were limitations in making comparisons.
The researchers tried to minimize the differences with detailed analysis that took into account a long list of demographics, pre-existing conditions, medication use, and nursing homes.
Another caveat is that the patients in the VA study were predominantly male and white, with an average age of 68 years, so it is unclear how generalized the results are.
One of the strengths of the research, experts say, is that it involves over 1.7 million patients with detailed electronic medical records, making it the largest study of Covid-related kidney problems to date.
While the results would most likely not apply to all Covid patients, for the study participants, they show that “it has a fairly remarkable long-term impact on kidney health in Covid-19 survivors, especially those who are very ill during their illness was”. acute illness, “said Dr. C. John Sperati, a nephrologist and associate professor of medicine at Johns Hopkins who was not involved in the study.
Other researchers have found similar patterns. “So this is not the only study that suggests these events take place after a Covid-19 infection,” he added.
He and other experts said that if even a small percentage of the millions of Covid survivors in the US developed permanent kidney problems, the health care impact would be big.
To assess kidney function, the research team assessed levels of creatinine, a waste product the kidneys are designed to remove from the body, and a measure of how well the kidneys are filtering blood called the estimated glomerular filtration rate.
Healthy adults gradually lose kidney function over time, about 1 percent or less per year starting at 30 or 40, said Dr. Wilson. Serious illnesses and infections can lead to a deeper or permanent loss of function, which can lead to chronic kidney disease or end-stage kidney disease.
The new study found that 4,757 Covid survivors had lost at least 30 percent of kidney function in the year after they were infected, said Dr. Al-Aly.
That’s roughly equivalent to “30 years of decline in kidney function,” said Dr. Wilson.
Covid patients were 25 percent more likely to achieve this decline than people who hadn’t had the disease, the study found.
Smaller numbers of Covid survivors had a bigger decline. However, Covid patients were 44 percent more likely than non-Covid patients to lose at least 40 percent of kidney function and 62 percent more likely to lose at least 50 percent.
220 Covid patients have been diagnosed with end-stage kidney disease, which occurs when at least 85 percent of kidney function is lost, said Dr. Al-Aly. Covid survivors were diagnosed almost three times as likely as those without Covid, according to the study.
Dr. Al-Aly and his colleagues also looked at a type of sudden kidney failure called acute kidney failure, which other studies have found in up to half of hospitalized Covid patients. The condition can heal without causing long-term loss of kidney function.
However, the VA study found that 2,812 Covid survivors suffered acute kidney injury months after being infected, almost twice as common as non-Covid patients, said Dr. Al-Aly.
Dr. Wilson said the new data supports the results of a study he and colleagues conducted on 1,612 patients that found that Covid patients with acute kidney damage had significantly worse kidney function than people with acute kidney injury from others in the months after leaving the hospital medical treatments conditions.
In the new study, the researchers didn’t directly compare Covid survivors to people infected with other viruses like the flu, which makes it hard to know “you are really sicker than if you just had another bad infection,” said Dr. Sperati.
In a previous study by Dr. However, Al-Aly’s team, who looked at many post-Covid health issues, including kidney problems, people hospitalized with Covid-19 had a significantly higher risk of developing long-term health problems in virtually any medicine category, including cardiovascular disease -, metabolic and gastrointestinal disorders when people were hospitalized with the flu.
Every type of kidney dysfunction measured in the new study was in Covid patients who were initially sicker – much more common – those who were in intensive care or had acute kidney damage in the hospital.
People who were less sick during their Covid hospital stay were less likely to have persistent kidney problems, but still significantly more often than non-Covid patients.
“People at the highest risk are the ones who got really bad in the beginning,” said Dr. Al-Aly. “But really, nobody is spared the risk.”
The study also found that even Covid patients who never had to be hospitalized were at slightly higher risk of kidney problems than the general VA patient population. But the risk seemed so small, said Dr. Sperati that “I don’t know if I would hang my hat on,” said Dr. Sperati.
Dr. Wilson found that some Covid patients who did not need hospitalization were still quite ill and had to stay in bed for days. He said it was possible that these were those who developed long-term kidney dysfunction, rather than people on the mildest end of the Covid spectrum.
Doctors aren’t sure why Covid can cause kidney damage. The kidneys may be particularly sensitive to flare-ups or activation of the immune system, or blood clotting problems, which are common in Covid patients, can affect kidney function, experts said.
Dr. Sperati said hospitalized Covid patients appeared to have a greater need for dialysis and more protein and blood in their urine than patients hospitalized with other serious illnesses.
“Covid is more likely to be a virus that is toxic to the kidneys,” said Dr. Wilson. “I think Covid Syndrome has some long-term kidney side effects.”