Kidney paired donation: fundamentals, limitations, and expansions.

Incompatibility between the candidate recipient and the prospective donor is a major obstacle to living donor kidney transplant. Kidney paired donation (KPD) can circumvent the incompatibility by matching them to another candidate and living donor for an exchange of transplants such that both transplants are compatible. KPD has faced legal, logistical, and ethical challenges since its inception in the 1980s. Although the full potential of this modality for facilitating transplant for individuals with incompatible donors is unrealized, great strides have been made. In this review article, we detail how several impediments to KPD have been overcome to the benefit of ever greater numbers of patients. Limitations and questions that have been addressed include blood group type O imbalance, reciprocal match requirements, simultaneous donor nephrectomy requirements, combining KPD with desensitization, the role of list-paired donation, geographic barriers, legal barriers, concerns regarding living donor safety, fragmented registries, and inefficient matching algorithms.