Ischemia time during partial nephrectomy has a different impact on renal function loss according to preoperative risk of acute kidney injury. Results from a prospective multicenter observational study (the RECORD2 project)

Aim of the study: Ischemia time during partial nephrectomy (PN) is among the greatest determinants of acute kidney injury (AKI). Whether the association between AKI and ischemia time might be affected by preoperative risk of AKI has never been investigated. Aim of the study was to assess whether the effect of ischemia time on functional deterioration might be affected by preoperative risk of AKI. Materials and methods: Data of 1,209 patients treated with PN for cT1 renal tumors were extracted from the RECORD2 database, a prospect- ive multicenter project. We estimated the individual risk of AKI according to variables available preoperatively, namely age, hyperten- sion, baseline renal function, PADUA score and surgical approach. The coefficients from multivariable model were used to build a nomogram for the prediction of AKI. Classification and regression tree (CART) analysis identified patients at “high” and “low” risk of AKI. Finally, we plotted the probability of AKI over ischemia time stratified by preoperative risk. Results: Overall, 294 (25%) patients had AKI stage RIFLE 1 (risk) after surgery. At multivariable analysis, older age, higher PADUA score, open surgery and better baseline function were associated with increased risk of AKI (all p < 0.0001). After cross validation, the discrimination accuracy of our model (AUC) was 68%. According to the first split at CART analysis, patients were categorized as “high” and “low” risk of AKI having a preoperative probability greater or smaller than 35%. The duration of ischemia affected the observed risk of AKI differently according to preoperative risk: as an example, in case of less than 10 vs more than 25 minutes of ischemia, low risk patients had a risk of AKI of 14% (95% confidence interval [CI]: 11%, 18%) and 28% (95%CI: 21%, 35%), respectively (absolute risk increase 13%; 95%CI: 5%, 22%; Figure 1). By contrast, the risk of AKI for high risk patients who had less than 10 vs more than 25 minutes of ischemia was 38% (95%CI: 26%, 49%) and 62% (95%CI: 48%, 76%), respectively. This corresponds to an absolute risk increase of 24% (95%CI: 1%, 46%).