Mild Increases in Plasma Creatinine after High-Risk Abdominal Surgery Are Associated with Long-Term Renal Injury: A Retrospective Cohort Study

Abstract

Background: The impact of mild acute kidney injury (AKI) observed in the immediate postoperative period after major surgery on long term renal function remains poorly defined. According to the “Kidney Disease: Improving Global Outcomes” (KDIGO) classification, a mild injury corresponds to a KIDIGO stage 1, characterized by an increase in creatinine of at least 0.3 mg/dl within a 48-hour window or 1.5 to 1.9 times the baseline level within the first week post-surgery. We tested the hypothesis that patients who underwent moderate-to high-risk abdominal surgery and developed mild AKI in the following days would be at an increased risk of long-term renal injury compared to patients with no postoperative AKI.Methods: In this single centre retrospective study, all consecutive adult patients with a plasma creatinine value ≤ 1.5 mg/dl who underwent high-risk abdominal surgery between 2014-2019 and who had at least three recorded creatinine measurements (before surgery, during the first seven postoperative days, and at long-term follow up [6 months-2 years]) were included. AKI was defined using a “modified” (without urine output criteria) KDIGO classification as mild (stage 1 characterised by an increase in creatinine of > 0.3 mg/dl within 48-hours or 1.5-1.9 times baseline) or moderate-to-severe (stage 2-3 characterised by increase in creatinine 2 to 3 times baseline or to ≥ 4.0 mg/dl). Development of long-term renal injury was compared in patients with and without postoperative AKI Results: Among the 815 patients included, 109 (13.4%) had postoperative AKI (81 mild [KDIGO 1] and 28 moderate-to-severe [KDIGO 2-3]). The median long-term follow-up was 360, 354 and 353 days for the three groups respectively (P=0.190). Patients who developed mild AKI had a higher risk of long-term renal injury than those who did not (odds ratio 3.1 [95%CI 1.7-5.5]; P<0.001). In multivariable analysis, mild postoperative AKI was independently associated with an increased risk of developing long-term renal injury (adjusted odds ratio 4.5 [95%CI 1.8-11.4]; P=0.002).Conclusions: Mild AKI after high-risk abdominal surgery is associated with a higher risk of long-term renal injury one year after surgery.