Frailty in the context of kidney transplantation.

Frailty, defined as an inappropriate response to stressful situations due to the loss of physiological reserve, was initially described in the elderly population, but is currently being identified in younger populations with chronic diseases, such as chronic kidney disease. It is estimated that about 20% of patients are frail at the time of kidney transplantation (KT), and there is great interest in its potential predictive value for unfavorable outcomes. A significant body of evidence has been generated; however, several areas still remain to be further explored. The pathogenesis is poorly understood and limited to the extrapolation of findings from other populations. Most studies are observational, involving patients on the waiting list or post-KT, and there is a scarcity of data on long-term evolution and possible interventions. We reviewed studies, including those with Brazilian populations, assessing frailty in the pre- and post-KT phases, exploring pathophysiology, associated factors, diagnostic challenges, and associated outcomes, in an attempt to provide a basis for future interventions.