Renal recovery after acute kidney injury

Abstract

Acute kidney injury (AKI) is a frequent complication of critical illness and carries a significant risk of short- and long-term mortality, chronic kidney disease (CKD) and cardiovascular events. The degree of renal recovery from AKI may substantially affect these long-term endpoints. Therefore maximising recovery of renal function should be the goal of any AKI prevention and treatment strategy. Defining renal recovery is far from straightforward due in part to the limitations of the tests available to assess renal function. Here, we discuss common pitfalls in the evaluation of renal recovery and provide suggestions for improved assessment in the future. We review the epidemiology of renal recovery and of the association between AKI and the development of CKD. Finally, we stress the importance of post-discharge follow-up of AKI patients and make suggestions for its incorporation into clinical practice. Summary key points are that risk factors for non-recovery of AKI are age, CKD, comorbidity, higher severity of AKI and acute disease scores. Second, AKI and CKD are mutually related and seem to have a common denominator. Third, despite its limitations full recovery of AKI may best be defined as the absence of AKI criteria, and partial recovery as a fall in AKI stage. Fourth, after an episode of AKI, serial follow-up measurements of serum creatinine and proteinuria are warranted to diagnose renal impairment and prevent further progression. Measures to promote recovery are similar to those preventing renal harm. Specific interventions promoting repair are still experimental.

Keywords: Acute kidney disease; Acute kidney injury; Biomarkers; Chronic kidney disease; Follow-up; Renal replacement therapy.

Fig. 1

Complex interrelationship between cardiovascular disease, acute kidney injury (AKI) and chronic kidney disease (CKD) as risk factors for end-stage renal disease (ESRD). High age, severe acute disease and possibly the modality of renal replacement therapy in patients with positive fluid balance are additional risk factors for progression to ESKD

Fig. 2

Pathophysiology of recovery

Fig. 3

AKI, AKD, CKD and time course of recovery. Recovery may occur early during acute kidney injury (AKI) up to 7 days after the insult, or later during acute kidney disease (AKD), between 7 days and 3 months after the insult to the kidney

Fig. 4

Potential scheme for follow-up of acute kidney injury (AKI) stages 2–3 complicating critical illness. Potential scheme for follow-up of acute kidney injury (AKI) stages 2–3 complicating critical illness. Serial assessments at 3 months and 1 year after AKI are required to establish the presence and severity of chronic kidney disease (CKD) and establish prognosis. In most cases, long-term follow-up and treatment can be achieved outside of specialist nephrology services following CKD management guidelines