 |
Transplants may be the patient's own tissue (autografts; eg, bone and skin grafts), genetically identical (syngeneic) donor tissue (isografts), genetically dissimilar donor tissue (allografts or homografts), or, rarely, grafts from a different species (xenografts or heterografts). Transplanted tissue may be cells (as for hematopoietic stem cell [HSC], lymphocyte, and pancreatic islet cell transplants), parts or segments of an organ (as for hepatic or pulmonary lobar transplants and skin grafts), or entire organs (as for heart transplants).
Tissues may be grafted to an anatomically normal site (orthotopic; eg, heart transplants) or abnormal site (heterotopic; eg, a kidney transplanted into the iliac fossa). Almost always, transplantation is done to improve patient survival. However, some procedures (eg, hand, larynx, tongue, and facial transplantation) attempt to improve quality of life but jeopardize quantity of life and thus are controversial.
With rare exceptions, clinical transplantation uses allografts from living related, living unrelated, or deceased donors. Living donors are often used for kidney and HSC transplants and increasingly for segmental liver, pancreas, and lung transplants. Use of deceased-donor organs (from heart-beating or non–heart-beating donors) has helped reduce the disparity between organ demand and supply; however, demand still far exceeds supply, and the number of patients waiting for organ transplants continues to grow.
Organ
distribution:
Allocation depends on disease severity for some organs (liver, heart) and on disease severity, time on the waiting list, or both for others (kidney, lung, bowel). In the US and Puerto Rico, organs are allocated first among 12 geographical regions, then among local Organ Procurement Organizations. If no recipient in the 1st region is suitable, organs are reallocated to recipients in other regions.
Last full review/revision November 2005
Content last modified November 2005
| |
