Introduction: We aimed to investigate frequency and predictors of renal function variation after radical nephroureterectomy (RNU) for upper tract urothelial carcinoma (UTUC) in a large multicenter cohort.
Methods: Patients underwent RNU at 17 tertiary centers Between 1994 and 2020 were included. Perioperative clinical factors were retrospectively collected. Estimated GFR was calculated using the CKD-EPI equation. Renal Function variation was
evaluated at I POD, 6 and 12 months follow up considering differences between timepoints as follows: ?1: I POD eGFR – baseline eGFR; ?2 (6 months eGFR-I POD eGFR); ?3 (12 months eGFR-6 months eGFR). We also defined I POD AKI as an increase in serum creatinine by = 0.3 mg/dl or a 1.5-1.9-fold increase in serum creatinine from baseline, according to the Acute Kidney Injury Network (AKIN) classification. Linear mixed models were used to evaluate the effect of clonical factors on eGFR variation and their interaction with follow-up time.
Results: After considered exclusion criteria, 576 were included. The median age was 72 years (IQR 64-79), median BMI was 26,2kg/m2 (IQR 24-29), 71% were male, 57,5% had smoking history, 46,5% had homolateral hydronephrosis. Pre-operative eGFR was 62.2 (IQR 48.1-79.9) mil/min/1,73. EBL was 170 (IQR 100-270) ml, OT 210 (180-255) min, 16.5% of patients had intraoperative complications, 50,8% had pT2 UTUC, and 4,6% had positive surgical margins. We found the following renal function variation at the considered timepoints ?1: -10,2 (-25.9; -2,2), ?2: 1.37 (-6.2; 9.0), ?3: 3 0.9 (-3.6; 5.2). In univariable linear mixed models, elderly patients had a positive eGFR variation after RNU compared to their younger counterpart (ß: 0.3±0.09, p=0.03), similarly those with hydronephrosis showed a positive eGFR variation after RNU (ß: 9.5±1.9, p<0.001). Conversely, RNU had a clinically meaningful detrimental effect on those with I POD AKI (ß:-32.6±1.7; p<0.001). During follow-up, the eGFR recovery was more pronounced in those with preoperative hydronephrosis (ß interaction: -3.4±0.9; p<0.001) and in those who experienced I POD AKI (ß interaction: 13.9±0.8; p<0.001). The capacity of elderly to recover was lower than their younger counterpart (ß interaction: -0.1±0.04, p=0.006). Multivariable regression model confirmed that age (ß 0.3 ± 0.1, p=0.002), hydronephrosis (ß: 3.7±1.8, p=0.039), I POD AKI (ß: -31.6±1.8, p<0.001) were independently associated to eGFR variation. In addition, all models confirmed a positive eGFR variation during follow-up as expression of contralateral kidney adaptation (ß: 10.3±2.9, p<0.001).
Conclusions: Our study shows that eGFR change magnitude varies according to age, pre-operative hydronephrosis and I POD AKI. Elderly patients might experience a smaller change in eGFR after surgery, but their younger counterpart could recovery better during follow-up.