REN and anemia: The Simple Postoperative AKI Risk (SPARK) score included age, gender, expected surgery duration, emergency operation, diabetes mellitus, use of renin-angiotensin-aldosterone inhibitors, baseline eGFR, albuminuria, hypoalbuminemia, anemia, and hyponatremia, and performed reasonably with an AUC of 0.80 (0.79–0.81) [50].