Acute kidney injury after partial nephrectomy: Role of parenchymal mass reduction and ischemia and impact on subsequent functional recovery

Background Acute increase of serum creatinine (SCr) after partial nephrectomy (PN) is primarily due to parenchymal mass reduction or ischemia; however, only ischemia can impact subsequent functional recovery. Objective We evaluate etiologies of acute kidney injury (AKI) after PN and their prognostic significance. Design, setting, and participants From 2007-2014, 83 solitary kidneys managed with PN had necessary studies for detailed analysis of function and parenchymal mass before/after surgery. AKI was classified by Risk/Injury/Failure/Loss/Endstage classification and defined by either standard criteria (comparison to preoperative SCr) or proposed criteria (comparison to projected postoperative SCr based on parenchymal mass reduction). Subsequent recovery was defined as percent function preserved/percent mass saved. Intervention PN. Outcome measurements and statistical analysis Predictive factors for AKI were evaluated by logistic regression. Relationship between AKI grade and subsequent functional recovery was assessed by linear regression. Results and limitations Median duration warm ischemia (n = 39) was 20 min and hypothermia (n = 44) was 29 min. Median parenchymal mass reduction was 11%. AKI occurred in 45 patients based on standard criteria and 38 based on proposed criteria, and reflected injury/failure (grade = 2/3) in 23 and 16 patients, respectively. On multivariable analysis, only ischemia time associated with AKI occurrence (p = 0.016). Based on the proposed criteria, median recovery from ischemia was 99% in patients without AKI and 95%/90%/88% for patients with grades 1/2/3 AKI, respectively. The coefficient for association between AKI grade based on proposed criteria and subsequent functional recovery was -4.168 (p = 0.018). Main limitation is limited patient cohort. Conclusions Parenchymal mass reduction and ischemia both contribute to acute changes in SCr after PN. Classification of AKI by proposed criteria significantly associates with subsequent functional recovery. However, more robust numbers will be needed to further assess the merits of the proposed criteria. While AKI is associated with suboptimal recovery, even patients with grade 2/3 AKI reached 88-90% of recovery expected. Patient summary Acute decline in function after partial nephrectomy associates with more prolonged ischemia time, and appears to impact subsequent functional recovery. However, most kidneys eventually recover strongly, even if their function is sluggish in the first few days after surgery.