Post-discharge kidney function is associated with subsequent ten-year renal progression risk among survivors of acute kidney injury

Abstract

The extent to which renal progression after acute kidney injury (AKI) arises from an initial step drop in kidney function (incomplete recovery), or from a long-term trajectory of subsequent decline, is unclear. This makes it challenging to plan or time post-discharge follow-up. This study of 14651 hospital survivors in 2003 (1966 with AKI, 12685 no AKI) separates incomplete recovery from subsequent renal decline by using the post-discharge estimated glomerular filtration rate (eGFR) rather than the pre-admission as a new reference point for determining subsequent renal outcomes. Outcomes were sustained 30% renal decline and de novo CKD stage 4, followed from 2003-2013. Death was a competing risk. Overall, death was more common than subsequent renal decline (37.5% vs 11.3%) and CKD stage 4 (4.5%). Overall, 25.7% of AKI patients had non-recovery. Subsequent renal decline was greater after AKI (vs no AKI) (14.8% vs 10.8%). Renal decline after AKI (vs no AKI) was greatest among those with higher post-discharge eGFRs with multivariable hazard ratios of 2.29 (1.88-2.78); 1.50 (1.13-2.00); 0.94 (0.68-1.32) and 0.95 (0.64-1.41) at eGFRs of 60 or more; 45-59; 30-44 and under 30, respectively. The excess risk after AKI persisted over ten years of study, irrespective of AKI severity, or post-episode proteinuria. Thus, even if post-discharge kidney function returns to normal, hospital admission with AKI is associated with increased renal progression that persists for up to ten years. Follow-up plans should avoid false reassurance when eGFR after AKI returns to normal.

Keywords: acute kidney injury; chronic kidney disease; epidemiology; mortality; prognosis; progression.

Figure 1

Renal progression after acute kidney injury (AKI) caused by renal decline (red solid line) or nonrecovery (pink dashed line). A patient with AKI who has incomplete post-episode recovery has a high risk of developing advanced chronic kidney disease (CKD) even if subsequent renal decline is slow (pink dashed line). However, the risk of advanced CKD in a patient with AKI who has near-complete recovery depends on whether he or she experiences subsequent decline at a rapid trajectory (red solid line). In both cases at a post-AKI reassessment review (time d), renal recovery and post-episode kidney function are already observable, but the risk of subsequent decline is uncertain. The vertical black dashed line at time d represents the start of follow-up in this study. eGFR, estimated glomerular filtration rate.

Figure 2

Flow diagram showing derivation of the cohort from the Grampian population. AKI, acute kidney injury; RRT, renal replacement therapy.

Figure 3

Crude long-term renal outcomes after a hospital admission episode with or without acute kidney injury (AKI). CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate.

Figure 4

Cumulative incidences of subsequent renal progression (solid line) for those with (red) and without (blue) an acute kidney injury (AKI) admission in 2003, grouped by postdischarge estimated glomerular rate (eGFR) and accounting for the competing risk of death (dashed line). (a,b) Subsequent sustained 30% renal decline; (c,d) new chronic kidney disease (CKD) stage 4.