Kidney transplantation or renal transplantation is the organ transplant of a kidney in a patient with chronic renal failure. The main types are cadaveric and living donor transplant. In the former, the kidney originates from a deceased person. In the latter, the kidney is being donated by an organ donor.

Occasionally, the kidney is transplanted together with the pancreas. This is done in patients with diabetes mellitus type I, in whom the diabetes is due to destruction of the beta cells of the pancreas and in whom the diabetes has caused renal failure (diabetic nephropathy). This is cadaveric by definition, as a living donor could not live without a pancreas.

The donor and recipient have to be HLA (tissue type) identical, and should ideally share as many "minor antigens" as possible. This decreases the risk of transplant rejection and need for dialysis and a further transplant. The risk of rejection after transplant may be reduced if the donor and recipient share as many HLA antigens as possible, if the recipient is not already sensitized to potential donor HLA antigens, and if immunosuppressant levels are kept in an appropriate range.

Problems after a transplant may include:

• Transplant rejection (hyperacute, acute or chronic)
• Infections and sepsis due to the immunosuppressant drugs that are required to decrease risk of rejection
• Post-transplant lymphoproliferative disorder (a form of lymphoma due to the immune suppressants)
• Imbalances in electrolytes including Calcium and Phosphate which can lead to bone problems amongst other things
• Other side effects of medications including gastrointestinal infammation and ulceration of the stomach and esophagus, hirsutism (excessive hair growth in a male-pattern distribution), hair loss, obesity, acne, diabetes mellitus (type 2), hypercholesterolemia and others.