The effect of cause, timing, kidney function recovery, and recurrent events on the prognosis of acute kidney injury in kidney transplant recipients

Aim: To assess the incidence of acute kidney injury (AKI) and its common etiologies in kidney transplant recipients and the effect of AKI's characteristics on graft survival. Methods: In a retrospective longitudinal cohort study, all serum creatinine (SCr) values of patients that had kidney transplantation between 01/2002-12/2010 were retrieved. AKI was defined as a 50% increase in SCr. Etiologies, recurrence, timing, and kidney function dynamics during the event were evaluated. The primary endpoint was defined as graft loss. Time-varying Cox model was used for the analysis. Results: Of 659 patients, 208 (31.6%) patients had 321 documented AKI events. Of these, 138 (66.4%) patients had one event, and 70 (33.6%) patients had recurrent events. The leading etiologies of the first AKI event were as follows: infection (33.4%), hypovolemia (14.3%), and unknown etiology (16.8%). Both first and recurrent AKI events were associated with an increased risk of graft loss (HR: 2.76, 95% CI: 1.95-3.89) and (HR: 4.54, 95% CI: 2.59-7.93), respectively. This deleterious association was lower within three months after transplantation, compared to later events. Patients in whom kidney function returned to baseline were less prone to graft loss. Conclusions: Late-onset, incomplete recovery, and recurrent AKI events are associated with increased graft loss.