Incidence and trajectories of subclinical and KDIGO-defined postoperative acute kidney injury in patients undergoing major abdominal surgery

<h2>Abstract</h2><h3>Background</h3> Postoperative acute kidney injury is a common occurrence among patients undergoing major abdominal surgery and is associated with adverse outcomes. The effect of an incremental increase in serum creatinine concentration not meeting the KDIGO criteria for acute kidney injury is poorly studied. We evaluated the incidence and trajectories of postoperative subclinical acute kidney injury (sPO-AKI), acute kidney injury (PO-AKI), acute kidney disease (PO-AKD), and their relationships with chronic kidney disease (CKD), major adverse kidney events (MAKE30), and all-cause mortality at 30 days after surgery. <h3>Methods</h3> In a pre-planned, nested cohort sub study of the Myocardial Injury in Noncardiac Surgery in Sweden (MINSS) study, we included 588 patients from two hospitals. We determined the incidence of PO-AKI, PO-AKD, and CKD according to the ADQI-POQI consensus criteria. sPO-AKI was defined as a 25–49% increase in serum creatinine concentration within 7 days of surgery. <h3>Results</h3> A total of 59 (10.2%) patients fulfilled the criteria for sPO-AKI, 41 (7.1%) patients for PO-AKI, 29 (6.2%) for PO-AKD, and 6 (1.2%) for CKD. Similar proportions of patients with sPO-AKI and PO-AKI developed PO-AKD. An association was identified between the combined group of sPO-AKI and PO-AKI and 30-day mortality (Cramer's V: 0.1, <i>P</i>=0.037). PO-AKD (Cramer's V: 0.4, <i>P</i><0.001) was associated with MAKE30 and 30-day mortality. All patients with CKD had pre-existing PO-AKD. <h3>Conclusions</h3> Subclinical postoperative kidney injury not fulfilling the KDIGO criteria occurred in every 10th patient, and one in 14 suffered from PO-AKI after major abdominal surgery. A majority of PO-AKD cases was preceded by sPO-AKI and PO-AKI. Early kidney injuries were associated with longer-term adverse outcomes including MAKE30, 30-day mortality, and CKD.