Bodily Organ Image Gallery
Bodily Organ Image Gallery

2009 HowStuffWorks

Introduction to How Organ Transplants Work

­Sixty years ago, scientists were on the cusp of a revolutionary scientific breakthrough. In the preceding decades, researchers had had some success transplanting organs in animals, and there had even been a few failed attempts at human organ transplants. Numerous studies showed that human organ transplantation was feasible, and that it would be enormously beneficial to thousands of patients, but nobody had been able to make it work.

Success finally came in the early 1950s, when several kidney transplants within a few years gave new life to ailing patients. In the following decades, doctors learned how to transplant other organs successfully, and they dramatically improved recovery rates. Today, most organ transplants are relatively safe, routine procedures, and transplantation is considered to be the best treatment option for thousands of patients every year.

Unfortunately, doctors and patients now face a new obstacle: The demand for transplants has far surpassed the supply of donated organs. Simply put, there aren't enough organ donors, so patients must wait months, even years, for their chance at recovery.

In this article, we'll look the three major processes involved in organ transplantation: the organ distribution system, the surgery itself and the post-surgery recovery. We'll also explore how scientists and politicians are working to remedy the organ-shortage problem.

The Screen, the List and the Match

Organ transplants are one option when a particular organ is failing. Kidney failure, heart disease, lung disease and cirrhosis of the liver are all conditions that might be effectively treated by a transplant. For problems with the heart, the lungs and other highly sensitive organs, a transplant is typically the course of last resort. But if all other avenues have been explored and the patient is willing and able, transplantation is a good, viable option.

Kidneys and livers may be transplanted from a living donor, since people are born with an extra kidney and the liver is regenerative. Even a lung can be transplanted from a living donor, but this is still very rare. For these procedures, a patient will generally find a willing donor in a friend or family member. If the donor is a match, they can proceed directly to the surgery stage. A smaller number of living transplants come from charitable people donating for the general good.

­If a patient needs a heart transplant, a double lung transplant, a pancreas transplant or a cornea transplant, they will need to get it from a cadaverous (deceased) donor. Generally, acceptable donors are people who are brain dead but on artificial life support. Even though they are technically dead, their body is still functioning, which means the organs remain healthy. Organs will deteriorate very quickly after the body itself expires, making them unusable for transplant.

In the United States, a patient who wants an organ transplant from a cadaverous donor must become part of an elaborate nationwide organ distribution system. This system, known collectively as the Organ Procurement and Transplantation Network (OPTN), is operated by the United Network for Organ Sharing (UNOS), an independent nonprofit organization working under contract with the U.S. Department of Health and Human Services.

UNOS maintains a database of eligible transplant patients awaiting organs as well as detailed information on all the organ transplant centers around the country. Additionally, the UNOS board of directors, primarily made up of transplant doctors, transplant patients and organ donors, establishes the policies that decide who will get which organs.

 

 

 

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Getting on the List

To be included on the national waiting list, a patient must first find a transplant team that will treat him or her. The transplant team, a group of surgeons, nurses and other health professionals at a hospital, evaluates the patient to decide whether he or she is a good candidate for transplantation. In addition to assessing the patient's physical condition, the team will consider the patient's attitude, psychological state and history of drug abuse, among other factors. Donated organs are a rare and precious commodity, so doctors don't want to proceed unless they are confident that a patient is physically and mentally prepared for the procedure, as well as life after the procedure. For the most part, patients who are unwilling to give up unhealthy drugs, including cigarettes and alcohol in many situations, will be automatically disqualified.

If the transplant team feels that a patient is a good candidate for transplant, they will contact the UNOS Organ Center in Richmond, VA, in order to put the patient on the national waiting list. The Organ Center operators record all relevant information about the patient, including his or her physical condition, blood type, tissue type and age. This information is entered into the national database.

When an organ becomes available (when an organ donor is pronounced brain dead at a hospital, typically), the local organ procurement organization (OPO) will gather all relevant information about the donor and enter this data into a program maintained by the UNOS Organ Center. Based on the criteria established by the UNOS board of directors, the program generates a ranked list of potential recipients. The criteria involves several factors, including the physical compatibility between the donor and the recipient, the health of the recipient and how long the recipient has been waiting for an organ. The purpose of the criteria is to choose a recipient who is a good match and stands a good chance of recovery, while also taking into account who has been "in line" longer.

The OPO will immediately contact the transplant team of the first person on the list. The transplant team will note all of the donor's information and make a decision whether or not to accept the organ. It may choose to decline the organ if it feels that the donor and potential recipient are not a close enough match or that the organ is unsatisfactory. For example, the donor may be much larger or older than the potential recipient, making the organ a bad fit, or the donor may have had health problems that could have damaged the organ. The transplant team might also decline the organ if the potential recipient is ill or otherwise unprepared for surgery. If the organ is declined, the OPO will move to the next name on the list.

In most cases, the OPO will first look for potential recipients in the local area. If there are no matches in the local area, the OPO will extend the search to anyone in the UNOS region (there are 11 regions across the country). If there are still no matches, the OPO will offer the organ to the person who is ranked first on the national list. The intention is to minimize organ transportation time and to encourage donation by offering donors a chance to help out their local community.

When a recipient's transplant team accepts the organ, things start moving pretty fast. The team tells the recipient to hurry to the hospital for surgery preparation, and another team is dispatched to remove the organs from the donor. In the next section, we'll see what is involved in both surgical procedures.

Organs from Overseas

The shortage of donated organs in the United States is so severe that many patients are seeking out transplants in other countries. In some countries, notably China, foreigners can buy the organs they need instead of waiting at home. These organs typically come from executed prisoners who have not volunteered to donate organs.

This situation is extremely controversial in the organ transplant community. Paying for organs is considered unethical in most Western nations, as is the recovery of organs if the donor has not agreed to donate them. Furthermore, there is strong indication that execution schedules are being modified to meet patient demand.

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The Surgery

When a donor's family authorizes the removal of organs, several surgical teams immediately begin work recovering the organ. (While the term harvesting is still in use, many organizations now prefer the term recovery because it is more sensitive to the donor family.) To understand what is involved in this procedure, let's focus on a particularly harrowing operation: the heart transplant.

­The first step for all the harvesting teams is to cut open the donor's chest. Next, a surgeon saws through the breast bone and pulls the ribs outward to reveal the heart. While other teams are working on other parts of the body, the heart team clamps the different blood vessels leading into the heart and pumps in a cold, protective chemical solution. This solution stops the heart from beating and helps preserve it during transportation.

The surgeons then sever the vessels and remove the heart from the body, placing it in a bag filled with a preservative chemical. This bag is then packed in an ordinary cooler filled with ice, which is rushed to the recipient's hospital, often via plane or helicopter.

Meanwhile, the recipient is fully anesthetized and his or her chest is shaved. He or she is wheeled into the surgery room and covered in sterile cloths, leaving only the chest exposed. Typically, the surgery won't actually begin until the heart arrives, just in case there is some problem in transport.

When the donated heart has arrived, the transplant team begins the procedure. First, they hook up an IV and inject an anticoagulant into the patient's bloodstream. This keeps the blood from clotting during the transplant procedure.

As with the recovery surgery, the team begins the surgery by making an incision in the patient's chest, sawing through the breastbone and pulling back the ribs. The doctors then hook up a heart-lung machine to the patient's body. The heart-lung machine's job, as you might expect, is to act as the patient's heart and lungs temporarily. The machine's plastic tubes are connected to blood vessels leading to and from the heart. Instead of being pumped to the lungs to get rid of carbon dioxide and pick up oxygen, blood returning to the heart is diverted to the machine. The machine drives the blood through a series of chambers to release carbon dioxide and pick up oxygen and then returns it into the body to be re-circulated. This enables the surgical team to remove the heart without disrupting respiration and circulation.

Additionally, the heart-lung machine can be adjusted to warm or cool the blood. During the operation, it is set to cool all the blood that passes through it. This cools the rest the body, which helps protect the other organs during the operation. Typically, the machine will have an attachment to suck up blood from the surgery area and send it directly back into the bloodstream.

When the blood has been effectively diverted around the heart and lungs, the surgeons remove the diseased heart by cutting it loose from the attached blood vessels. The back walls of the atria, the upper chambers of the heart, are actually left in place. The surgeons remove the back walls of the donor heart's atria and suture the donor heart to the remaining tissue of the old heart. Then they suture the blood vessels formerly leading to the diseased heart to the vessels leading out of the donor heart.

After the new heart is in place, the team gradually warms up the blood flowing through the patient's body. As the body warms a little, the heart may start beating on its own. If it does not, the team applies an electrical shock to get it going. The team lets the new heart and the heart-lung machine share the job of circulating blood for some time, giving the heart time to build strength.

If everything is working correctly, the team wires the halves of the breast bone back together and stitches up the patient's chest using dissolving stitches. The patient is hooked up to a ventilator and brought to the recovery room. In a few hours, most patients regain consciousness. They may be ready to leave the hospital within a week.

Typically, the entire procedure only takes about five hours. But patients have to work the rest of their lives to make sure the donated organ continues to function. In the next section, we'll find out what is involved in this post-transplant treatment.

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Living with a New Organ

As with most other surgeries, recovery from a transplant operation involves additional medication and hospital visits to make sure the incisions heal correctly. But while other surgery patients typically can move on from the experience, most transplant recipients must continue medical treatment for the rest of their lives. This is because of the immune system's reaction to the new organ.

Your immune system comprises all the elements in your body that keep bacteria, microbes, viruses, toxins and parasites from destroying your organs and tissues. In other words, the immune system works to destroy any harmful foreign matter that ends up in your body. When the system is working correctly, it can distinguish most foreign cells from cells produced by the body. (See How Your Immune System Works to find out how it does this.)

A transplanted organ is made entirely of foreign cells, of course, which means the body will attack it if left to its own devices. To minimize the immune response, transplant teams make sure donors and recipients have matching blood and tissue types. But even with a good match, the body will see the new cells as foreign matter and reject the organ (destroy it cell by cell). Only tissue from an identical twin will be fully accepted.

There are three types of rejection that might occur following a transplant:

  • Hyperacute rejection occurs as soon as the donated organ is in the body. This only happens if there are already antibodies in the recipient's bloodstream that react to the new organ, which would occur if the blood types of the donor and recipient were incompatible for some reason. This almost never happens, since transplant teams always test for any incompatibility ahead of time. If it were to happen, the recipient would most likely die on the operating table.
  • Acute rejection occurs at least a few days after the transplant, after the body has had time to recognize the foreign material. This is the normal immune response to foreign matter.
  • Chronic rejection is a very gradual rejection, lasting months or years. It can be so subtle that the patient doesn't notice any ill effects for some time.

Acute Rejection

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The chief obstacle to living with a transplant is acute rejection. This sort of rejection would happen to nearly all recipients if it weren't for immunosuppressive drugs. As you might expect, immunosuppressive drugs generally suppress elements of the immune system so they do not attack the donor organ. The problem with this is that the drugs also suppress some of the beneficial things the immune system does. A person taking immunosuppressive drugs is much more susceptible to infection and disease.

A new approach may eventually change this course. In a few experimental cases, kidney transplant patients have also received bone marrow transplants from their donors. Bone marrow produces the white blood cells that play a crucial role in guarding the body against foreign matter. The theory behind this new approach is that the white cells from the donor marrow will merge with the recipients's natural cells, allowing the immune system to recognize the new organ as part of the body. The initial experimental results are encouraging. The first test subjects are doing very well without taking any immunosuppressive drugs.

Drugs are still the main course of action, however, and they do yield good results. Typically, a transplant team prescribes specific combinations of drugs to patients in order to achieve the right balance of suppression. The goal is to suppress the system just enough to prevent rejection, while minimizing side effects and the risk of infection. The transplant team usually adjusts the drug prescription over time, fine-tuning it to the patient's needs. In some cases, the patient may eventually be weaned off all drugs as the body adapts to the new organ, but this is extremely rare.

Transplant patients must be vigilant about taking their medication, and they must visit the hospital regularly for follow up tests. But it is worth it in most cases -- patients who have been sick for many years due to a diseased organ may feel completely rejuvenated following a transplant.

Unfortunately, thousands of people never get this chance at a new life. In the next section, we'll find out why this is and look at a few possible solutions.

A Fair Trade

The United Network for Organ Sharing is trying out a promising new organ exchange program as an incentive to encourage kidney donation. In this program, someone who wants to donate a kidney to a friend or family member but is not a match can donate to another transplant patient in order to move his or her loved one up on the waiting list.

Donors can either arrange an exchange with a matching family in the same situation or they can donate the organ into the general pool in exchange for a cadaver kidney. Obviously, this arrangement directly benefits the specific recipients, but it also benefits the transplant community as a whole since more kidneys are donated into the system. Check out Initiative May Shorten Wait For Kidney Transplant for more information.

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Improving the System

Forty years ago, countless people died because doctors could not successfully perform a transplant and prevent rejection. The knowledge of immunosuppressive drugs was minimal, and the surgery involved was extremely difficult.

Today, science has advanced to the point that most transplant operations are considered relatively low risk. The success rate is phenomenal for kidney transplants, liver transplants, cornea transplants, pancreas transplants -- even heart and lung transplants. But more than 5,000 potential transplant recipients die in the United States every year, not because of scientific obstacles, but because of social ones.

In the United States, the vast majority of the population is in favor of organ donation, but only a small percentage of people actually end up donating their organs when they die. There aren't anywhere near enough organs to meet the demand, which means an average of 16 potential recipients die every day from a curable condition.

This is partly due to human psychology and partly due to donation consent laws. Under current U.S. law, the final decision to donate a deceased person's organs is left to whoever has power of attorney or to the person's family. Organ donor cards or organ donor indications on a driver's license are important legal documents, but the consent of family members takes precedence.

Naturally, most people don't want to dwell on the thought of their own death, so few take the time to discuss their feelings about organ donation with their families. When it comes time to make the decision, the family members aren't sure what to do. They may be so troubled by the thought of surgeons cutting their loved one's body that they decline to donate the organs.

The main problem, then, is that donating organs requires at least two people to take decisive action that may be uncomfortable. The donor must take the initiative to talk to his or her family and the family must take the initiative to adhere to the donor's wishes. If these things don't happen, and in the majority of cases they don't, nobody gets to use those organs.

This has created a national medical crisis in the United States, and hundreds of surgeons, scientists and politicians are clamoring for a solution. One interesting possibility is xenotransplantation, the transplantation of organs between different species. The study of xenotransplantation is still in the early stages, but there have been some promising results. It is not a totally viable alternative at this time for a number of reasons. Chiefly, many scientists are worried that transplants between animals and humans could introduce new diseases into the human population. Xenotransplantation is also problematic ethically, as it would involve killing animals for their organs.

Another interesting avenue is the development of artificial organs. But while there have been tremendous advances in this field over the past decade, artificial organs don't work nearly as well as natural organs for most patients. It is still a very young science.

At this time, many doctors and politicians suggest legal and social changes as the best option. In some European and Asian nations, it is automatically assumed that you are an organ donor unless you notify the government that you do not want to be. Few people take this necessary action, and this has greatly increased the supply of available organs. Many feel that the United States should follow this model, but the idea has met with a lot of resistance. It would mean exerting greater control over people's bodies.

Most experts agree that the ideal solution to the problem would be a shift in national consciousness. To this end, the United Network for Organ Sharing, the American Medical Association, the National Institute of Health and many other organizations have stepped up efforts to educate the public about the benefits of donation. These groups hope that if more people understand the need for organs and the tremendous benefit of donation, they will begin to see donation as their social responsibility. They will understand that organ transplantation is truly one of the most remarkable achievements of modern science, and that organ donation is among the greatest opportunities to serve humanity.

For more information about organ transplants and related topics, check out the links on the next page.