Every year, tens of thousands of Americans receive new organs, giving them a new lease on life when the ones they were born with start to fail. In 2016 there were more than 33,600 transplants, a number that has risen by 20 percent in the past five years.
However, there are many more than that waiting on the transplant list — about 120,000 people total. Sometimes they wait for years; an average of about 8,000 people die every year waiting for the organs they need. Researchers, doctors and policymakers are exploring new strategies to increase the supply of organs needed to meet the demand.
Part of the reason for the shortfall is that not all donated organs can be used. One factor is the standard method of transport and storage. There is a short window of time to get the organ to the recipient in time. Another problem is mismatching donors to recipients. In response, there is a movement afoot to find tech solutions to combat the crisis.
Most transplantable organs come from deceased donors, and once an organ becomes available, doctors have just a few hours to find a recipient and complete the transplant. "Once an organ is procured, the clock starts ticking," says David Klassen, the chief medical officer at the United Network for Organ Sharing (UNOS). The longer an organ stays outside the body and on ice, the worse it functions, putting the recipient at risk of complications. Sometimes if it takes too long or a donated organ doesn't meet the standards mandated by medical protocols, it must simply be discarded.
UNOS is the organization responsible for organ allocation, and they are constantly working to improve the way they allocate organs for transplantation. Each organ has a different policy, and the allocation algorithms are built around these policies, says Anne Paschke, a spokesperson for UNOS. Programmers and testers create the algorithm from scratch and make sure it works before it is implemented.
Unlike algorithms used by places like Facebook or Netflix, which incorporate machine learning or artificial intelligence, UNOS' algorithm compares complex and multifaceted medical and logistical factors, such as the patient's blood type and antigens, and logistical factors such as distance and medical urgency, to match donors to recipients.
The problem of organ allocation is complicated, and some experts are working to create algorithms that can match donors to recipients even more efficiently. "The way organs are offered to individual centers and they decide whether to accept them or not, it's a bit slow," says Jesse Schold, the director of outcomes research in kidney transplantation at the Cleveland Clinic.
"Certainly, there is more to learn regarding behavioral aspects of decision-making, how information is disseminated, and other alterations in the allocation algorithm" that may make the process more efficient and less prone to waste, he says.
The equation gets more complex when donors are offered organs that may come with a higher risk of infectious disease or poorer function, such as those that come from older donors or donors with risky behaviors, like drug use. Patients have to agree to accept one of these organs, and though they might be reluctant to accept an organ labeled "high risk," studies show that most of these organs function just fine, and patients who accept them fare much better than those who keep waiting.
More recently, the use of medical marijuana has sparked a debate, because potential recipients who have used marijuana become ineligible to receive a transplant due to risk of infection, even if a doctor had prescribed the marijuana.
"Every patient wants the very best organ out there. But the reality is that all organs are different, and they potentially all have issues," Klassen says. "For a patient who is looking at long waiting times, it's better to take an organ that is less than ideal but they have access to much more quickly, as opposed to waiting for a perfect organ, which may take a long time or it may never come."
Allocation algorithms that improve upon those currently used by UNOS would likely prioritize certain clinics based on factors like how likely they would be to accept a high-risk organ. "There's a trade-off between giving all transplant centers and candidates on their list a chance to accept that organ versus making an algorithm that says probabilistically a particular center is most likely to accept this organ based on past behavior or who is on their list," says Schold of the Cleveland Clinic. The challenge comes in trying to allocate these organs efficiently and also fairly.
If researchers are successful, these same calculations and questions will look a lot different in the future. Several new techniques could extend the time an organ stays viable outside the body, which could help give doctors more time to find recipients and decrease the number of organs that are underutilized. One technique, called norothermic perfusion, keeps an organ continually awash in a solution similar to the one that would be found in the body at room temperature. Though the idea behind the technique has been around since transplants were first possible, researchers have greatly improved upon it to even repair organs before they are implanted.
Shaf Keshavjee, a transplant surgeon at Toronto General Hospital Research Institute, developed norothermic perfusion. Keshavjee designed the technique initially for lungs — a special machine keeps lungs doused in a solution to keep them damp, as well as a reverse version of a ventilator so the lungs are effectively breathing outside the body. So far, the technique has kept lungs viable for 20 hours outside the body, more than triple the typical time of six hours. That extra time also allows doctors to treat the organs to reduce the risk of rejection or transmission of infectious disease to the recipient.
Since 2010, when Keshavjee did a TED talk that introduced the technique to the world, his clinic alone has completed more than 300 transplants with lungs treated this way, and he estimates another 180 more have been done at other clinics, in Vienna and Paris. The use of the technique has expanded beyond lungs to include livers, hearts and kidneys. In some cases, norothermic perfusion can even improve function of organs, such as kidneys, that had previously worked too poorly to be transplanted into a patient. The equipment for this type of perfusion is new and expensive, but Keshavjee is collaborating with a manufacturer to make the technology easier to use and more affordable so that more clinics can access it, he says.
Policy changes from agencies that regulate hospitals and transplantation centers could also help get donated organs to where they're most needed. Changes to the hospital reimbursement system, for example, could encourage more centers to accept high-risk organs, Schold suggests. Education campaigns on the benefits of accepting high-risk organs (or changing that terminology to something less ominous, like "increased risk") and changing the way organ transplant centers are compensated, regulated and evaluated could have a big impact, Schold says.
There are other, far more distant techniques that may someday close the gap between the supply of transplantable organs and their demand. Scientists are working to develop a technique of xenotransplantation, or growing organs in other animals that could be viable in humans. One of the major hurdles continues to be immunological — the organs grown in pigs, the most promising candidates so far, have cells that cause the human immune system to reject the transplanted organ.
Other researchers are creating artificial organs that can be grown in the lab. Most organs are made from a number of different cells that have to work in concert, and growing them to the right size and function to be implanted is still a challenge. Those avenues won't be available in the near future, though researchers have started making progress in developing them.
So how close are we to having enough organs to meet the demand of recipients? Klassen suspects the gap between supply and demand will be there for the foreseeable future — that is, until we can start expanding the pool of possible organs beyond those in humans.
"The gap [between the number of donors and recipients] will be there for a while," he says. The new initiatives and techniques, he adds, are certainly steps in the right direction. "I think there's a lot of potential we're not quite capturing yet, and there's a lot of work to be done there."
— By Alexandra Ossola, special to CNBC.com