Fig. 5

Forest plot for postoperative acute kidney injury (AKI) (defined as the proportion of patients who developed postoperative worsening of renal function, whichever definition was used by the authors of the included studies). Studies were split into 2 different subgroups, according to the risk of perioperative morbidity/mortality. Low risk was defined as elective surgery in young, ASA I-II patients. Definition of high risk was based on the need of emergent surgery, and/or elective major surgery in patients with risk criteria defined by perioperative scoring system, ASA physical status classification (i.e., ASA III–IV), age > 60 years, and preoperative morbidity. Size of squares for odds ratio reflects weight of trial in pooled analyses. Horizontal bars represent 95% confidence intervals