2.2. Renal Function Monitoring

We selected the Modification of Diet in Renal Disease (MDRD) equation [13] to calculate eGFR, because it does not rely on patient’s weight, which we believe was often underestimated because, in our current practice, the value is provided by the patient itself.

Chronic kidney disease (CKD) ≥ stage 3 according to the National Kidney Foundation criteria [13] was preoperatively registered. We reported AKI onset for both the “risk” (R-AKI) and “injury” stages (I-AKI) (eGFR decreases > 25% and >50%, respectively) based on the RIFLE criteria [7], in order to analyze the association of both stages with overall survival and CKD ≥ stage 3 onset during follow-up. Unlike standard RIFLE criteria, we only considered eGFR and not urine output, since the latter was not always correctly measured during the in-hospital stay.

Both eGFR and serum creatinine were noted preoperatively, at 24–48 h after the intervention, before discharge, and every six months thereafter. During follow-up, we reported cases of CKD onset with a stage ≥ 3 [13], and cases of eGFR deterioration with decreases both superior to 25% and 50%. If a major renal function decline was detected from laboratory testing, patients were also addressed to a nephrologist.