Two years ago, a donated kidney shipped from Florida to a recipient in North Carolina missed a flight connection in Atlanta. When the kidney finally arrived at the transplant center, surgeons had just 46 minutes to spare, almost rendering the organ unusable.

Each year in the U.S., nearly 5,000 people die waiting for a kidney transplant, with wait time heavily dependent on where a person lives. At the same time, an estimated 3,500 donated kidneys are discarded because they’re no longer viable. This troubling imbalance of organ scarcity and massive wastefulness is tied in part to limited organ sharing across the country. Current policies prioritize local matching, and surgeons are often reluctant to accept donated kidneys that require multiple flight connections.

Inefficient organ sharing can also have a ripple effect. Surgeons waiting for a kidney that misses a flight connection and becomes unviable could have been operating on another patient. In this case, patients, the surgeon, and the transplant center all lose.

Policymakers have tried to address these complex problems by eliminating the current system’s regional boundaries, allowing organs to travel further. “But geographical distance isn’t the only thing that matters,” says Ronghuo Zheng, a Texas McCombs assistant professor of accounting.

Along with Tinglong Dai of Johns Hopkins University and Guihua Wang of The University of Texas at Dallas, Zheng set out to investigate whether the introduction of a new airline route could increase the number of kidneys shared across long distances. The researchers found the answer to be a resounding yes. The study is the first effort of its kind to understand the role of airline logistics in organ transplantation.

A Rise in Kidney Sharing

Zheng and his colleagues began by merging airline transportation data from the U.S. Bureau of Transportation Statistics with figures on U.S. kidney transplant candidates, donors, and recipients from the nonprofit UNOS, the United Network for Organ Sharing. Not all organs travel on commercial flights — hearts, for example, are typically transported on private planes because they only survive for four to six hours outside the body — but kidneys do because they last longer.

In their research, airline data spanned from 2002 to 2017 and gave a complete picture of direct flight options between any two airports in the United States. The researchers focused on airport pairs with a flying distance of at least 800 miles. Kidneys traveling short distances often don’t rely on commercial flights, but on helicopters or vehicles.

Kidney transplant data covered 2003 to 2017 and included information on patient demographics and how long a transplant candidate survived after receiving a new kidney. The percentage of male candidates was 40%, and the average donor age was 39. Researchers were able to calculate the total number of kidney transplants involving a donor and recipient connected by an airport pair for each year.

Ultimately, Zheng and colleagues analyzed a group consisting of 61 airport pairs and a control group of 513 airport pairs over 16 years. They estimated that the introduction of a new airline route increases the overall number of shared kidneys by 7.3%.

Results by city pairs were revealing. In 2014, restrictions against Southwest Airlines from flying beyond Texas and its four surrounding states were lifted, and the airline introduced a new route between Baltimore-Washington International Thurgood Marshall Airport and Dallas Love Field Airport. That same year, the average number of kidney shares between the two airports jumped from 1.7 to eight.

In 2011 when a new route was introduced between Charleston International Airport and Nashville International Airport, the number of kidneys from donors in Charleston to Nashville recipients jumped from three in 2011 to five in 2012 to 12 in 2013.

Creating a More Equitable System

The researchers’ findings not only show better kidney sharing, they also suggest that introducing new direct airline routes reduces the discard rate of kidneys by 0.6%.

“Transportation has an outsized impact,” Zheng says.

The effect of introducing a new daytime route, the researchers found, is slightly greater than that of introducing a new evening route. That’s probably because a majority of organ donation tends to happen in the evening or early morning. Day flights allow enough time to get a kidney from the daytime flight arrival location to the transplant location.

New weekday routes also made a bigger impact than weekend routes, the researchers found. Their study, however, shows no evidence that introducing new airline routes would worsen the post-transplant outcome for organ recipients. This result shows the improvement in the quantity of shared organs does not come at a cost of lower quality.

Zheng’s research helps to inform organ transplantation policymakers on the logistical issues hindering the U.S. transplantation system, and it offers a solution. If airlines add more direct flights, organ sharing can be boosted and waste reduced. Patients in San Antonio, for example, where the average wait time for a kidney is currently around five years, might be able to receive one sooner.

Better transportation can also help create more equity when it comes to who gets a donated organ, since where a recipient lives becomes less important, Zheng says. To further improve the process, U.S. policymakers should consider establishing a national system that initiates and tracks organ shipments through commercial airlines, the researchers say.

“Airline transportation matters,” Zheng says. “Ultimately, donated organs won’t save or improve lives unless they’re accepted, transported, and transplanted.”

Does Transportation Mean Transplantation? Impact of New Airline Routes on Sharing of Cadaveric Kidneysis forthcoming, online advance in Management Science.

Story by Deborah Lynn Blumberg