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Things have looked up for U.S. kidney transplant recipients over the past few decades, according to a review article.

In adult kidney transplant recipients, the total number of transplants from living and deceased donors in the U.S. jumped from 45,008 in 1996-1999 up to 76,885 in 2016-2019, reported Sundaram Hariharan, MD, of the University of Pittsburgh School of Medicine, and colleagues.

This uptick was largely driven by a rise in the number of transplants from deceased kidney donors, from 29,823 in 1996 to 53,139 in 2019, they stated in the .

And there also was an increase in living kidney donor transplants, jumping from 15,185 in 1996 to 23,746 in 2019, according to the authors.

"There has been a gratifying improvement in kidney transplant survival, both for patients and the kidney graft itself, from 1996 to the current era," Hariharan explained in a statement. "These improvements have occurred despite unfavorable increases in obesity, diabetes and other conditions in patients and donors."

However, the higher number of deceased kidney donors stems largely from deaths related to the opioid epidemic, the group pointed out, although the demand for kidney transplants still continues to overshadow the supply.

The authors evaluated kidney transplant trends, and found that the median age of donor recipients increased a bit over time, from a median of 48 in 1996 to 55 in recent years. The median age increased from 42 to 52 by 2019 in living donor recipients.

The split between male and female recipients held fairly steady over time, though, at roughly 60% male and 40% female.

Of note, white patients made up over half of all deceased donor kidney recipients in 1996 and more than 70% of all living donor recipients. By 2019, the distribution of deceased donors became more equal among racial and ethnic groups, as white patients accounted for 37% of recipients and Black patients represented 34%. However, the distribution of living donor recipients held steady over time, vastly in favor of white patients.

Over the past few decades, the incidence of delayed graft function decreased in living donor kidneys, dropping from 5.2% in 1996 to 2.9% in 2019. However, this increased from 25.5% of deceased donor kidneys to 29.3% in 2019.

The researchers pointed out that kidneys from deceased donors with high scores on the Kidney Donor Profile Index are more likely to have delayed graft function, which puts the kidney at a higher risk for premature failure. They added that although the use of mild hypothermia in brain-dead donors has been shown to lower the rates of delayed graft function, this strategy hasn't been widely adopted in regular clinical practice quite yet.

"Long-term graft survival of kidneys from deceased donors can be improved by reducing the severity of perfusion injury with a shorter cold ischemia time, especially for kidneys with high scores on the Kidney Donor Profile Index," they recommended.

Despite nearly 30% of deceased donor kidneys experiencing delayed graft function, Hariharan's group said these kidneys are still quite valuable, particularly for patients who may have a shorter life expectancy.

Both graft and patient survival rates became more favorable over the past few decades. Specifically, deceased donor kidney 10-year overall graft survival rate improved form 42.3% in 1996 to 53.6% in 2011. Meanwhile, the 10-year patient survival rate increased from 60.5% in 2006 to 66.9% by 2011.

Overall, the top causes of transplant failure, not including patient death, were alloimmune injury and recurrent glomerulonephritis. The top causes of death with a functioning graft within the first year post-transplant were cardiovascular disease (CVD, 31% of deaths), infection (31%), and cancer (7%). After the first year following a transplant, the top causes of death were cancer (29%), CVD (23%), and infection (12%).

"We have learned a lot through research and by taking care of kidney transplant patients," Hariharan noted. "Newer tissue typing and tissue matching platforms, changes in organ allocation systems, living donor paired exchanges, transplant surgical techniques, immunosuppressive medications, anti-viral medications, refined diagnostic methods of kidney rejection by biopsy, aggressive post-transplant surveillance and overall post-transplant medical management have contributed to better survival rates."

But in order to continue this upward post-transplant survival trend, a "multipronged approach" is necessary, spearheaded by both nephrologists and primary care physicians, the authors emphasized. This will take a combination of bolstering health literacy, greater access to caregivers, and more stringent adherence to therapy, particularly for racial or ethnic minority recipients, as well as for young transplant recipients, they said.

The authors added that "Innovative noninvasive biomarkers to diagnose and prevent acute rejection, adoptive T-cell therapy for post-transplantation viral infections, and newer therapies for T-cell-mediated rejection, antibody-mediated rejection, and desensitization are under investigation" can continue to improve these transplant outcomes.

Another recent win for kidney transplant recipients was the 2020 , which will likely spur more favorable outcomes in years to come. The law gives lifelong health coverage for long-term immunosuppressive medications for transplant patients.

"The passing of this law is a great victory for kidney transplant patients, and we anticipate further improvements in long-term kidney transplant survival over the next decade," said Hariharan.

The researchers also recommended that kidney transplant recipients receive their third COVID-19 vaccine booster -- recently FDA authorized for immunocompromised individuals -- as another strategy to bolster survival rates during the pandemic.

"It's also very important that kidney transplant patients follow Centers for Disease Control and Prevention guidelines on social distancing and masking," Hariharan stated.

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