The 5 most common types of transplants (and their characteristics)

The Navarra University Clinic (CUN) defines a transplant as the implantation of an organ or tissue from one living being to another or, failing that, from one place to another of the same organism. There are many clinical events that may require a transplant to be addressed, but the most common of all is irreparable organ failure. When the kidneys or liver stop working, it's time to sign up for a transplant list.

In 2007, some 275,000 Europeans were living with a transplanted organ or tissue. With a higher average general life expectancy, more chronic pathologies appear in the population, and this is reflected numerically: in countries like France, the need for transplants increased by 45% from 2000 to 2007, for example.

In any case, organ transplantation also has its macabre face, beyond the reported life expectancy. As of today, 107,000 Americans are on the waiting list for an organ, added to a new patient every 10 minutes and about 20 people die every 24 hours without receiving treatment appropriate.

A transplant gives a new lease of life to the patient, but the lack of viable organs causes thousands of unintentional deaths. In the US, in 2015, almost 5,000 people died waiting for a kidney transplant. With these data in hand, we tell you everything you need to know about the most commonly used types of transplants.

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What are the types of transplants?

This issue can be addressed in many ways, since it is possible to group the types of transplantation according to the place of the implant, the relationship of the patient with the donor or the methodology used, among others criteria.

1. autologous transplants

To begin, we will say that An autologous transplant is one that is performed within the same organism, that is, the recipient and donor are the same individual..

An example of an autologous transplant is the collection of stem cells from a neoplastic patient prior to chemotherapy. So that they are not damaged during the procedure, they are extracted from the individual's bone marrow and, after the chemo, they are reintroduced into their body. The great advantage of autotransplants is that there is no possibility that the patient will reject them, since he is interacting with her own tissue.

2. Isotransplants

On the other hand, isotransplants are those that occur between different individuals but practically the same at the genetic level, as is the case with monozygotic twins. There is almost no risk of rejection.

3. Xenografts

Another variant are xenotransplants, where the donor and recipient are from different species. For example, aortic valve repair and replacement in humans can be done with transplants made from porcine or bovine tissue.

4. allogeneic transplants

In fourth and last place, we have allogeneic or typical transplants, known all over the world. In this case, donor and recipient are of the same species, but with different genomes.

The most common allogeneic transplants

Below, we present the most common types of allogeneic transplants in today's society.

1. kidney transplant

Kidney transplants are the most common and necessary in today's society. In the United States, some 3,000 patients are added to waiting lists each month, and in countries like Spain, more than 2,500 procedures of this nature are performed per year, well above the rest of organs.

The kidneys are essential for the functioning of the organism, since they allow us to filter toxins from the blood and promote the maintenance of homeostatic balance, by regulating electrolytes circulating. When the kidney fails severely, dialysis can be used, but transplantation is the definitive option.

kidney transplant has a success rate of 90%, even more so if the donor is related to the recipient at the genetic level. Unfortunately, the biggest problem is found in the scarcity of these organs in public health agencies. It is not surprising, since the prevalence of chronic kidney disease has grown by 30% in the last 10 years.

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2. Liver transplant

In Spain, the second place is occupied by liver transplantation, with some 1,034 procedures per year. The liver is the largest internal organ and performs several functions critical to our well-being., including processing nutrients, drugs, and hormones, producing bile (which secretes bilirubin and helps digest food), make protein, remove bacteria and toxins from the blood, and many more things. It is literally impossible to live without a liver.

Liver transplantation **is used for critical patients with hepatitis B and C, alcoholic cirrhosis, non-alcoholic fatty liver disease and many other pathologies **more. Survival rates 5 years after the procedure are estimated at 80% in adults and 90% in children, respectively.

3. lung transplant

To compare with the rest of the figures, some 336 lung transplants are performed annually in Spain. This number is much lower than in the rest of the procedures, since it is only carried out when absolutely all possible treatments have failed and the patient's life is in serious danger.

Unfortunately, the survival rates are not as hopeful as in the other cases: 79% survive one year after the transplant, 64% after 3 years and only 30% after 10 years after the operation.. Acute rejection is almost a universal problem in the first year, whereas bronchiolitis obliterans limits long-term survival. For all these reasons, lung transplantation is never an ideal situation.

4. Heart transplant

In Spain, about 278 heart transplants are performed each year. This procedure can be used to address serious organ damage after a heart attack, to stop failure when medications no longer work, to treat serious cardiac abnormalities that prevent proper blood pumping and for abnormal heartbeats. As hard as it sounds, these types of procedures are hardly conceived for people over 70 years of age, since younger patients have priority.

Survival rates 20 years after transplantation are 20-25%. The heart is an extremely complex organ and, therefore, it is common for failures to arise such as rejections by of the recipient, problems with the arteries, conditions in the primary graft and proclivity to suffer certain infections. For all these reasons, the patient's prognosis is not very positive in the long term.

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5. pancreas transplant

In Spain, fewer than 100 pancreas transplants are performed per year. Finland has the highest European rate, with 7 procedures per million inhabitants per year, but it is still a very low figure. It is used for some types of diabetes that are uncontrollable with conventional treatments, frequent reactions to insulin, severe kidney damage and other pathologies.. In many cases, pancreas and kidney transplants are performed simultaneously.

This situation is very curious, since it is estimated that 85% and 75% of patients survive pancreas transplantation after 1 and 5 years, respectively. These data reaffirm that all patients with life-threatening type 1 diabetes mellitus should be candidates for a pancreas transplant, but this is not the case.

This underuse of the technique is attributed to the lack of knowledge on the part of general practitioners and, in many cases, due to the high rate of discarded organs when they arrive at the centers, due to their deteriorated macroscopic appearance (50%).

Summary

As you can see, the journey of a patient requiring a transplant is not an easy one. We have told you what happens to those who manage to be recipients of an organ (the most "lucky" ones) and even so, their survival rates drop drastically over the years. Many transplants are "expired", as they last from 10 to 20 years and, after that, all that remains is to hope that the patient does not die.

This is the most hopeful scenario, since that of many other thousands of people is, directly, dying while waiting. We rely on data to bring this painful statement, and it is that 35% of the people on the transplant lists in the world die due to lack of resources. Maybe it's time to consider becoming donors, don't you think?

Bibliographic references:

• Bezinover, D., & Saner, F. (2019). Organ transplantation in the modern era.
• Desschans, B., Evrard, P., & of the Belgian, C. T. S. (2014, November). Organ donation and transplantation statistics in Belgium for 2012 and 2013. In Transplantation proceedings (Vol. 46, No. 9, p. 3124-3126). Elsevier.
• Number of organ transplants performed in Spain in 2020, by type, Statista. Collected on April 8 in https://es.statista.com/estadisticas/596378/numero-de-trasplantes-de-organos-realizados-en-espana-por-tipo/
• Organ Donation and Transplantation Statistics, National Kidney foundation. Collected on April 8 in https://www.kidney.org/news/newsroom/factsheets/Organ-Donation-and-Transplantation-Stats
• What is a stem cell transplant (bone marrow transplant), Cáncer.net. Collected on April 8 in https://www.cancer.net/es/desplazarse-por-atenci%C3%B3n-del-c%C3%A1ncer/c%C3%B3mo-se-trata-el-c%C3%A1ncer/qu%C3%A9-es-el-trasplante-de-c%C3%A9lulas-madre-trasplante-de-m%C3%A9dula-%C3%B3sea
• Randall, T. (1991). Too few human organs for transplantation, too many in need... and the gap widens. Jama, 265(10), 1223-1227.
• Types of organ transplant, Narayan Health. Collected on April 8 in https://www.narayanahealth.org/organ-transplant/