For patients waiting for a new liver or heart, the organ transplant list can be anguishing but there may be a better way. Scientists are working on the ability to create custom-made organs.

People can neither be too healthy, negating a need for a new organ while another person might have a greater need, nor too sick, meaning that the body may be more likely to reject the organ and the surgery might be futile. People often wait on the organ transplant lists for years, with no end in sight.

Then, when an organ becomes available, and is ostensibly a match, there is always the risk that the body rejects the organ – an uncomfortable, painful ordeal that can mean that the entire process may need to start all over again.

With the organ transplant list so fraught with heartbreak, there may come a point where the time needed to grow an organ is less than the time spent waiting on the organ transplant list.

While it may sound like science fiction, scientists are well on their way to achieving this reality. In Sweden, a group of scientists have created a custom-made vein to transport blood from a girl’s liver to her intestines that has operated for a year, and is still going strong. In Japan, researchers implanted livers grown from human cells into mice. They work just as how they would in humans. In 1998, Dr. Anthony Atala was part of a team that implanted a bladder into children, created from cells collected from the children themselves. The cells gathered amounted to the size of a postage stamp, and the children still have these bladders.

But science still has a way to go to reach the aspirations these hopefuls have. Scientists do best currently with flat, simple structures, like skin, which consists of only one type of cell. Scientists can also create tubal structures involving two cell types, like blood vessels. Most recently, scientists have been able to create hollow organs like the stomach, which consists of two cell types but has a more complicated shape. Solid organs, however, like the kidney elude scientists right now. They contain many cell types, and require more blood vessels to stay alive than an organ like the stomach. Dr. Atala was part of a team that, in 2010, successfully created a solid liver, but it has not yet been tested on humans.

Dr. Atala's team announced that they have successfully created “scaffolds” out of pig kidneys, which can one day be used to engineer new kidneys for human patients in the Annals of Surgery. While this is a bold new step, the use of pig organs for human bodies is not a new one – pig heart valves have been used in place of human heart valves for years. This advance paves the way for a solution in organ donation. There are currently 90,000 patients waiting on the organ transplant list for kidneys.

Regardless, doctors and studies in the field hold out hope, and conduct many different studies. With a custom-made organ, there runs no risk of a dreaded organ rejection – and patients are guaranteed a match.