Mild Acute Kidney Injury after Noncardiac Surgery Is Associated with Long-term Renal DysfunctionA Retrospective Cohort Study

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Perioperative acute kidney injury is commonIt is unclear whether this merely represents a transient increase in creatinine or has prognostic value WHAT THIS ARTICLE TELLS US THAT IS NEW: Patients with mild postoperative kidney injury (stage I) after noncardiac surgery had an estimated 2.4 times higher odds of having long-term renal dysfunction compared with patients without postoperative kidney injuryA quarter of patients who had stage I acute kidney injury postoperatively still had stage I kidney injury 1 to 2 yr later, and an additional 11% had even worse renal function BACKGROUND:: Perioperative acute kidney injury is common. However, it is unclear whether this merely represents a transient increase in creatinine or has prognostic value. Therefore, the long-term clinical importance of mild postoperative acute kidney injury remains unclear. This study assessed whether adults who do and do not experience mild kidney injury after noncardiac surgery are at similar risk for long-term renal injury. METHODS: This study is a retrospective cohort analysis of adults having noncardiac surgery at the Cleveland Clinic who had preoperative, postoperative, and long-term (1 to 2 yr after surgery) plasma creatinine measurements. The exposure (postoperative kidney injury) and outcome (long-term renal injury) were defined and staged according to the Kidney Disease: Improving Global Outcomes (KDIGO) initiative criteria. The primary analysis was for lack of association between postoperative kidney injury (stage I vs. no injury) and long-term renal injury. RESULTS: Among 15,621 patients analyzed, 3% had postoperative stage I kidney injury. Long-term renal outcomes were not similar in patients with and without postoperative stage I injury. Specifically, about 26% of patients with stage I postoperative kidney injury still had mild injury 1 to 2 yr later, and 11% had even more severe injury. A full third (37%) of patients with stage I kidney injury therefore had renal injury 1 to 2 yr after surgery. Patients with postoperative stage I injury had an estimated 2.4 times higher odds of having long-term renal dysfunction (KDIGO stage I, II, or III) compared with patients without postoperative kidney injury (odds ratio [95% CI] of 2.4 [2.0 to 3.0]) after adjustment for potential confounding factors. CONCLUSIONS: In adults recovering from noncardiac surgery, even small postoperative increases in plasma creatinine, corresponding to stage I kidney injury, are associated with renal dysfunction 1 to 2 yr after surgery. Even mild postoperative renal injury should therefore be considered a clinically important perioperative outcome.