A RECENT study presented at UK Kidney Week examined recovery after acute kidney injury (AKI), suggesting that how clinicians define “recovery” may have important implications for predicting long-term outcomes, including kidney failure and death.
Why AKI Recovery Definitions Matter for Long-Term Outcomes
Researchers led by Dr Samuel Strain and Professor Nicholas Selby from Royal Derby Hospital and the Centre for Kidney Research and Innovation at the University of Nottingham analysed data from a prospective observational cohort of 506 patients who developed AKI during hospitalisation and were followed for five years. Their aim was to determine which definition of kidney function recovery best predicts clinically meaningful outcomes.
Recovery after AKI is widely recognised as an important determinant of long-term prognosis. However, previous studies have used a broad range of thresholds, defining recovery as serum creatinine returning to within anywhere between 10% and 50% of a patient’s baseline level. The lack of consensus has made it difficult to apply evidence consistently in clinical practice.
Researchers Compare Different AKI Recovery Thresholds
In this secondary analysis, the investigators tested several definitions of recovery based on the percentage increase in serum creatinine at three months after AKI compared with the patient’s pre-AKI baseline. Thresholds ranged from full recovery (return to baseline) up to a 30% increase in creatinine. Outcomes assessed included kidney failure, mortality, and a combined endpoint of kidney failure or death. Kidney failure was defined as doubling of serum creatinine, initiation of kidney replacement therapy, or an estimated glomerular filtration rate below 15 ml/min/1.73 m².
Participants had a mean age of 71 years, and nearly 59% were male. At baseline, the mean eGFR was 69 ml/min/1.73 m², while 28.5% had chronic kidney disease. During the index admission, 58.1% experienced stage 1 AKI, 25.3% stage 2, and 16.6% stage 3.
Over five years of follow-up, 5.5% of patients developed kidney failure, 26.3% died, and 29.4% experienced the combined outcome. Notably, defining recovery as creatinine returning fully to baseline did not show a significant association between non-recovery and long-term outcomes.
However, when recovery was defined as creatinine returning to within 10% of baseline, patients who failed to meet this threshold had a significantly higher risk of kidney failure and of the combined outcome of kidney failure or death. As the threshold for recovery widened toward a 30% increase in creatinine, the risks of adverse outcomes rose progressively, and mortality also became independently associated with non-recovery.
The findings suggest that failure to recover kidney function after AKI is strongly linked to poorer long-term outcomes, and that a definition of recovery within 10% of baseline creatinine at three months may provide a clinically meaningful benchmark for both research and patient care pathways.
Reference
Strain S, Selby N. AKI recovery and 5 year outcomes. UKKW, 10-12 March, 2026.
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