Noninvasive Diagnosis of Kidney Allograft Rejection

Despite regular conventional monitoring of kidney transplant recipients, allograft rejection remains a barrier for the long-term success of kidney transplantation and is one of the leading causes of graft failure. Kidney transplant rejection and graft failure are reported as the most feared outcomes by patients. Timely diagnosis of rejection and early treatment enables interventions that may attenuate alloimmune processes before irreversible graft injury has occurred. The evolving landscape of noninvasive diagnostic tools presents promising opportunities for early detection of kidney allograft rejection. These tools, alone or combined, may promptly signal the need for a biopsy, reduce the need for surveillance biopsies, or even potentially inform treatment monitoring. Therefore, they are of utmost importance, and their use should be informed by evidence, guiding both patients and their clinical teams. This review will cover noninvasive tests used for the diagnosis of kidney allograft rejection available or soon to be available in the clinical setting and describe their diagnostic context, strengths, and limitations, while proposing an ideal clinical framework for their use.