Organ transplantation is the moving of an organ from one body to another or from a donor site to another location on the patient's own body, for the purpose of replacing the recipient's damaged or

Organ transplantation

Organ transplantation is the moving of an organ from one body to another or from a donor site to another location on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be re-grown from the patient's own cells (stem cells, or cells extracted from the failing organs). Organs and/or tissues that are transplanted within the same person's body are calledautografts. Transplants that are recently performed between two subjects of the same species are called allografts. Allografts can either be from a living or cadaveric source.

Organs that can be transplanted are the heart, kidneys, liver, lungs, pancreas, intestine, and thymus. Tissues include bones, tendons (both referred to as musculoskeletal grafts), cornea, skin, heart valves, nerves and veins. Worldwide, the kidneys are the most commonly transplanted organs, followed by the liver and then the heart. Cornea and musculoskeletal grafts are the most commonly transplanted tissues; these outnumber organ transplants by more than tenfold.

History.

The first successful corneal allograft transplant was performed in 1837 in a gazelle model; the first successful human corneal transplant, a keratoplastic operation, was performed by Eduard Zirm at Olomouc Eye Clinic, now Czech Republic, in 1905. The first transplant in the modern sense – the implantation of organ tissue in order to replace an organ function – was a thyroid transplant in 1883. It was performed by the Swiss surgeon and later Nobel laureate Theodor Kocher.

At the same time, organs were also transplanted for treating diseases in humans. The thyroid gland became the model for transplants of adrenal and parathyroid glands, pancreas, ovary, testicles and kidney. By 1900, the idea that one can successfully treat internal diseases by replacing a failed organ through transplantation had been generally accepted.^[8] Pioneering work in the surgical technique of transplantation was made in the early 1900s by the French surgeon Alexis Carrel, with Charles Guthrie, with the transplantation of arteries or veins. Their skillful anastomosis operations and the new suturing techniques laid the groundwork for later transplant surgery and won Carrel the 1912 Nobel Prize in Physiology or Medicine. From 1902, Carrel performed transplant experiments on dogs. Surgically successful in moving kidneys, hearts, and spleens, he was one of the first to identify the problem of rejection, which remained insurmountable for decades.

Types of transplant[edit]

Autograft[edit]

Main article: Autotransplantation

Autografts are the transplant of tissue to the same person. Sometimes this is done with surplus tissue, tissue that can regenerate, or tissues more desperately needed elsewhere (examples include skin grafts, vein extraction for CABG, etc.). Sometimes an autograft is done to remove the tissue and then treat it or the person before returning it (examples include stem cell autograft and storing blood in advance of surgery). In arotationplasty, a distal joint^{[ disambiguation needed ]} is used to replace a more proximal one; typically a foot or ankle joint is used to replace a knee joint. The patient's foot is severed and reversed, the knee removed, and the tibia joined with the femur.

Allograft and allotransplantation[edit]

Main article: Allotransplantation

An allograft is a transplant of an organ or tissue between two genetically non-identical members of the same species. Most human tissue and organ transplants are allografts. Due to the genetic difference between the organ and the recipient, the recipient's immune system will identify the organ as foreign and attempt to destroy it, causing transplant rejection. The risk of transplant rejection can be estimated by measuring the Panel reactive antibody level.

Isograft[edit]

A subset of allografts in which organs or tissues are transplanted from a donor to a genetically identical recipient (such as an identical twin). Isografts are differentiated from other types of transplants because while they are anatomically identical to allografts, they do not trigger an immune response.

Xenograft and xenotransplantation[edit]

Main article: Xenotransplantation

A transplant of organs or tissue from one species to another. An example is porcine heart valve transplant, which is quite common and successful. Another example is attempted piscine-primate (fish to non-human primate) transplant of islet (i.e. pancreatic or insular tissue) tissue. The latter research study was intended to pave the way for potential human use if successful. However, xenotransplantion is often an extremely dangerous type of transplant because of the increased risk of non-compatibility, rejection, and disease carried in the tissue.

Split transplants[edit]

Sometimes a deceased-donor organ, usually a liver, may be divided between two recipients, especially an adult and a child. This is not usually a preferred option because the transplantation of a whole organ is more successful.

Domino transplants[edit]

In patients with cystic fibrosis, where both lungs need to be replaced, it is a technically easier operation with a higher rate of success to replace both the heart and lungs of the recipient with those of the donor. As the recipient's original heart is usually healthy, it can then be transplanted into a second recipient in need of a heart transplant.^[18] Another example of this situation occurs with a special form of liver transplant in which the recipient suffers from familial amyloidotic polyneuropathy, a disease where the liver slowly produces a protein that damages other organs. The recipient's liver can then be transplanted into an older patient for whom the effects of the disease will not necessarily contribute significantly to mortality.^{[19][ spam link? ]}

This term also refers to a series of living donor transplants in which one donor donates to the highest recipient on the waiting list and the transplant center utilizes that donation to facilitate multiple transplants. These other transplants are otherwise impossible due to blood type or antibody barriers to transplantation. The "Good Samaritan" kidney is transplanted into one of the other recipients, whose donor in turn donates his or her kidney to an unrelated recipient. Depending on the patients on the waiting list, this has sometimes been repeated for up to six pairs, with the final donor donating to the patient at the top of the list. This method allows all organ recipients to get a transplant even if their living donor is not a match to them. This further benefits patients below any of these recipients on waiting lists, as they move closer to the top of the list for a deceased-donor organ. Johns Hopkins Medical Center in Baltimore and Northwestern University's Northwestern Memorial Hospital have received significant attention for pioneering transplants of this kind.^[20][21]

In February 2012, the last link in a record 60-person domino chain of 30 kidney transplants was completed.^[22][23]

ABO-incompatible transplants[edit]

Main article: ABO-incompatible transplantation

Because very young children (generally under 12 months, but often as old as 24 months,^[24]) do not have a well-developed immune system,^[25] it is possible for them to receive organs from otherwise incompatible donors. This is known as ABO-incompatible (ABOi) transplantation. Graft survival and patient mortality is approximately the same between ABOi and ABO-compatible (ABOc) recipients.^[26] While focus has been on infant heart transplants, the principles generally apply to other forms of solid organ transplantation.^[24]

The most important factors are that the recipient not have produced isohemagglutinins, and that they have low levels of T cell-independent antigens.^[25][27] United Network for Organ Sharing (UNOS) regulations allow for ABOi transplantation in children under two years of age if isohemagglutinin titers are 1:4 or below,^[28][29] and if there is no matching ABOc recipient.^[28][29][30] Studies have shown that the period under which a recipient may undergo ABOi transplantation may be prolonged by exposure to nonself A and B antigens.^[31] Furthermore, should the recipient (for example, type B-positive with a type AB-positive graft) require eventual retransplantation, the recipient may receive a new organ of either blood type.^[24][29]

Limited success has been achieved in ABO-incompatible heart transplants in adults,^[32] though this requires that the adult recipients have low levels of anti-A or anti-B antibodies.^[32] Kidney transplantation is more successful, with similar long-term graft survival rates to ABOc transplants.^[29]

Transplantation in Obese Individuals[edit]

Until recently, patients labeled as obese were not considered appropriate candidates for renal transplantation. In 2009, the physicians at the University of Illinois Medical Center performed the first robotic kidney transplantation in an obese recipient and have continued to transplant patients with Body Mass Index (BMI)’s over 35 using robotic surgery. As of January 2014, over 100 patients that would otherwise be turned down because of their weight have successfully been transplanted.^{[33] [34]}

Major organs and tissues transplanted[edit]

Main article: Transplantable organs and tissues

Thoracic organs[edit]

· Heart (deceased-donor only)

· Lung (deceased-donor and living-related lung transplantation)

· Heart/Lung (deceased-donor and domino transplant)

Abdominal organs[edit]

· Kidney (deceased-donor and living-donor)

· Liver (deceased-donor and living-donor)

· Pancreas (deceased-donor only)

· Intestine (deceased-donor and living-donor)

· Stomach (deceased-donor only)

· Testis^[35]

Tissues, cells, fluids[edit]

· Hand (deceased-donor only), see the first recipient Clint Hallam

· Cornea (deceased-donor only) see the ophthalmologist Eduard Zirm

· Skin, including face replant (autograft) and face transplant (extremely rare)

· Islets of Langerhans (pancreas islet cells) (deceased-donor and living-donor)

· Bone marrow/Adult stem cell (living-donor and autograft)

· Blood transfusion/Blood Parts Transfusion (living-donor and autograft)

· Blood Vessels (autograft and deceased-donor)

· Heart Valve (deceased-donor, living-donor and xenograft [porcine/bovine])

· Bone (deceased-donor and living-donor)

Types of donor[edit]

Organ donors may be living or may have died of brain death or circulatory death. Most deceased donors are those who have been pronounced brain dead. Brain dead means the cessation of brain function, typically after receiving an injury (either traumatic or pathological) to the brain, or otherwise cutting off blood circulation to the brain (drowning, suffocation, etc.). Breathing is maintained via artificial sources, which, in turn, maintains heartbeat. Once brain death has been declared the person can be considered for organ donation. Criteria for brain death vary. Because less than 3% of all deaths in the U.S. are the result of brain death, the overwhelming majority of deaths are ineligible for organ donation, resulting in severe shortages.

Organ donation is possible after cardiac death in some situations, primarily when the patient is severely brain injured and not expected to survive without artificial breathing and mechanical support. Independent of any decision to donate, a patient's next-of-kin may decide to end artificial support. If the patient is expected to expire within a short period of time after support is withdrawn, arrangements can be made to withdraw that support in an operating room to allow quick recovery of the organs after circulatory death has occurred.

Tissue may be recovered from donors who die of either brain or circulatory death. In general, tissues may be recovered from donors up to 24 hours past the cessation of heartbeat. In contrast to organs, most tissues (with the exception of corneas) can be preserved and stored for up to five years, meaning they can be "banked." Also, more than 60 grafts may be obtained from a single tissue donor. Because of these three factors—the ability to recover from a non-heart beating donor, the ability to bank tissue, and the number of grafts available from each donor—tissue transplants are much more common than organ transplants. TheAmerican Association of Tissue Banks estimates that more than one million tissue transplants take place in the United States each year.

Living donor[edit]

In living donors, the donor remains alive and donates a renewable tissue, cell, or fluid (e.g., blood, skin), or donates an organ or part of an organ in which the remaining organ can regenerate or take on the workload of the rest of the organ (primarily single kidney donation, partial donation of liver, lung lobe, small bowel). Regenerative medicine may one day allow for laboratory-grown organs, using patient's own cells via stem cells, or healthy cells extracted from the failing organs.

Deceased donor[edit]

Deceased donors (formerly cadaveric) are people who have been declared brain-dead and whose organs are kept viable by ventilators or other mechanical mechanisms until they can be excised for transplantation. Apart from brain-stem dead donors, who have formed the majority of deceased donors for the last 20 years, there is increasing use of donation-after-circulatory-death-donors (formerly non-heart-beating donors) to increase the potential pool of donors as demand for transplants continues to grow.^{[ citation needed ]} Prior to the recognition of brain death in the 1980s, all deceased organ donors had died of circulatory death. These organs have inferior outcomes to organs from a brain-dead donor;^[36] however, given the scarcity of suitable organs and the number of people who die waiting, any potentially suitable organ must be considered.

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