Organ transplantation is the surgical transfer of an organ, or a functional part of one, from a donor into a recipient to replace lost or severely impaired function. It is an established branch of medicine involving surgery, donor assessment, organ preservation, and continuing care. Transplantation can treat acute or chronic organ failure, but its feasibility depends on the recipient’s condition, the availability of a suitable organ, and the risks of treatment. The principal solid organs transplanted are kidneys, liver, heart, lungs, pancreas, and intestines. (who.int)
Scope and clinical purpose
Different transplants restore different functions. A kidney transplant replaces the filtering and regulatory functions lost in kidney failure. Liver, heart, and lung transplantation can provide treatment when organ failure cannot be adequately managed by other means. For suitable kidney recipients, transplantation generally offers better survival and quality of life than dialysis, although it is a treatment rather than a guarantee of permanent recovery. (niddk.nih.gov)
Solid-organ transplantation is distinguished from transplantation of tissues, such as corneas, skin, and heart valves, and from transplantation of blood-forming stem cells obtained from bone marrow or other sources. Hand and face transplants are classified as vascularized composite allografts: they transfer several tissue types, including skin, muscle, nerves, bone, and blood vessels, together as a functional unit. (organdonor.gov)
Historical development
A major milestone occurred in 1954, when a team at Boston’s Peter Bent Brigham Hospital performed the first successful human kidney transplant between twin brothers. The identical-twin setting largely avoided the immunological incompatibility that had obstructed earlier transplantation attempts. Joseph E. Murray’s contributions to organ transplantation were recognized with a share of the 1990 Nobel Prize in Physiology or Medicine. (brighamandwomens.org)
Subsequent improvements in surgical techniques, preservation, and control of rejection made transplantation between genetically different individuals increasingly practicable. These developments also increased demand for donated organs, making procurement and allocation central components of transplantation services. (iris.who.int)
Donors and organ procurement
Organ donation may come from living or deceased donors. Living donation most commonly involves one kidney or a portion of the liver. Donation of a lung lobe or portions of the pancreas or intestine is much less common. Living donors undergo assessment of their medical suitability and the risks of donation; donation itself carries surgical and other health risks. (organdonor.gov)
Deceased donation may follow confirmation of death by neurological criteria, commonly described as brain death, or by circulatory criteria. These pathways require different arrangements for maintaining organ suitability and arranging retrieval. They are distinct from living donation, in which donor safety and voluntary participation are essential considerations. (nhsbt.nhs.uk)
Kidney paired donation allows incompatible donor–recipient pairs to exchange donors with other pairs. A willing donor who cannot donate directly to an intended recipient may thereby make possible a compatible transplant for that recipient. Exchanges can involve two or more pairs. (organdonor.gov)
Compatibility and allocation
Compatibility testing examines blood group and tissue characteristics. Human leukocyte antigens, the human form of the major histocompatibility complex, are important markers in tissue matching. A crossmatch tests donor material against recipient blood to help identify immune incompatibility before transplantation. A close match reduces rejection risk but does not normally eliminate it. (medlineplus.gov)
Allocation is not simply a chronological queue. In the United States, organ-specific policies consider factors including blood type, body size, medical urgency, waiting time, and distance between hospitals. Kidney allocation also considers tissue matching and crossmatch results. The relative importance of these factors differs by organ because clinical needs and preservation constraints differ. (organdonor.gov)
Preservation and transplantation
Between retrieval and implantation, organs require preservation to maintain their suitability. Established methods include preservation solutions, cold storage, and pumping systems. Preservation limits vary by organ and influence transport arrangements and recipient selection. (organdonor.gov)
Machine perfusion circulates fluid through an organ outside the body. Normothermic systems can supply oxygen and nutrients at approximately body temperature, allowing functional assessment during preservation. Such technologies are used to improve organ utilization and investigate whether organs that might otherwise be discarded can be transplanted successfully. (nhsbt.nhs.uk)
Rejection and immunosuppression
Transplant rejection occurs when the recipient’s immune system recognizes donor antigens as foreign and attacks the graft. Rejection is commonly described as hyperacute, acute, or chronic. Hyperacute rejection develops rapidly after transplantation; acute rejection can impair graft function; chronic rejection involves progressive damage over a prolonged period. Compatibility testing and anti-rejection treatment reduce these risks. (medlineplus.gov)
Most recipients require long-term immunosuppression. Drugs used include calcineurin inhibitors such as tacrolimus and cyclosporine, corticosteroids, and other agents. Suppressing immune activity protects the graft but increases susceptibility to infection and certain forms of cancer. Some immunosuppressive drugs also contribute to diabetes and other metabolic complications. (niddk.nih.gov)
Continuing clinical monitoring assesses graft function, rejection, and treatment complications. Rejection may begin before noticeable symptoms appear, making laboratory surveillance important. Graft failure may require renewed organ-support treatment or another transplant; successful implantation does not end the need for continuing care. (niddk.nih.gov)
Ethical framework
Transplantation depends on informed consent, donor protection, and transparent allocation. The World Health Organization’s guiding principles, endorsed in May 2010, establish an ethical framework for acquiring and transplanting human cells, tissues, and organs. WHO identifies equitable access, protection against commercial exploitation, quality, safety, and transparency as central concerns for transplantation systems. (who.int)