Acute Kidney Injury After Nephrectomy:a New Nomogram To Predict Postoperative Renal Function

Objective: Acute kidney injury(AKI)is an inevitable disease with high mortality for nephrectomy,which can increase the risk of chronic kidney disease(CKD).However,current guidelines for post-nephrectomy follow-up are based on oncologic risk rather than renal function,and there is no consensus regarding the criteria of renal function monitoring and AKI recovery.Therefore,the aims of this study were to compare effects of transient AKI,subacute acute kidney injury(AKD)and persistent AKI on CKD progression,and to develop and validate visual Nomogram models using variables routinely available in clinics,which could accurately assess the risk of AKI,AKD and CKD after nephrectomy.Methods: This retrospective study included a derivation cohort of 1559 patients and a validation cohort of 713 patients between July 2012 and June 2019.Derivation cohort was used to build prediction models and validation cohort was used to assess discrimination and calibration of models.Patients were divided into normal renal function group,transient AKI group,subacute AKD group and persistent AKI group,and were followed up for at least three months to assess postoperative renal function.Forward stepwise regression and multivariate Cox regression analyses were used to estimate independent risk factors associated with AKI,AKD and CKD.Incorporating all statistically significant predictors,three Nomogram models for postoperative AKI,AKD and CKD were developed and validated,respectively.Discrimination was calculated using the area under the receiver operating characteristic curve(AUC).We assessed calibration visually,plotting predicted probability and observed absolute risk of the postoperative AKI,AKD and CKD.Results: The incidence of postoperative kidney injury was 28.96%,of which transient AKI,subacute AKD and persistent AKI were 13.91%,7.83% and 7.22%,respectively.Compared with normal renal function patients,patients suffered postoperative kidney injury had a longer length of stay and a significantly higher proportion of CKD.The risk for AKD progression escalated in a graded manner related to the AKI severity(stage 1 30.75% vs.stage 2 64.71% vs.stage 3 100%),patients with both radical nephrectomy(RN)and postoperative AKI had the highest AKD probabilities than those with AKI or RN alone.Patients suffered persistent AKI(HR 4.61,95%CI 3.03-7.01,P < 0.01)had a higher risk of CKD than those with subacute AKD(HR 1.83,95%CI 1.17-2.86,P < 0.01)or transient AKI(HR 2.54,95%CI 1.58-4.08,P < 0.01).Increasing age(HR 1.30,95%CI 1.12-1.51,P< 0.01),high level of uric acid(HR 1.18,95%CI 1.01-1.37,P < 0.05)and diuretics(HR1.71,95%CI 1.37-2.14,P < 0.01)were risk factors of postoperative AKI,partial nephrectomy(PN)(HR 0.46,95%CI 0.34-0.62,P < 0.01)was protective factor of it.According to AKD and CKD Nomograms,increasing age(AKD: HR 1.32,95%CI 1.12-1.56,P < 0.01;CKD: HR 1.60,95%CI 1.27-2.01,P < 0.01),RN(AKD: HR 1.52,95%CI1.03-2.25,P < 0.05;CKD: HR 1.79,95%CI 1.13-2.83,P < 0.05),and the usage of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker(AKD: HR 1.61,95%CI 1.12-2.33,P < 0.05;CKD: 1.66,95%CI 1.09-2.53,P < 0.05)were risk factors of both AKD and CKD progression.High level of baseline e GFR(HR 0.29,95%CI 0.23-0.37,P < 0.01)was associated with decreased risk of progression to CKD.In terms of complications,anemia(HR 2.98,95%CI 2.22-4.00,P < 0.01)and obesity(HR 1.85,95%CI1.38-2.50,P < 0.01)were risk factors of AKD,while hypertension(HR 1.46,95%CI 1.02-2.09,P < 0.05)and hyperuricemia(HR 1.65,95%CI 1.16-2.36,P < 0.01)were risk factors of CKD.The AUC were 0.68(95%CI 0.63-0.73,P < 0.01),0.84(95%CI 0.79-0.88,P <0.01)and 0.86(95%CI 0.82-0.90,P < 0.01)for the prediction of AKI,AKD and CKD in the validation cohort,showing high discrimination of models.And calibration plots revealed good agreement between predicted probability and the observed absolute risk.Conclusion: Increasing age,high level of uric acid and diuretics were risk factors of postoperative AKI,while PN was associated with decreased AKI risk.The risk for AKD progression escalated in a graded manner related to the AKI severity,patients with both RN and AKI had the highest AKD probabilities than those with AKI or RN alone.Patients suffered persistent AKI had a higher risk of CKD than those with subacute AKD or transient AKI.The Nomograms accurately predict AKD and CKD in patients underwent nephrectomy,which can timely intervene and correct reversible risk factors to reduce sustained renal damage.