#6668 PREDICTION OF REMAINING RENAL FUNCTION IN PATIENTS UNDERGOING RADICAL NEPHRECTOMY DUE TO RENAL TUMOUR MASS AND AFTER NEPHRECTOMY IN LIVING DONORS
Authors: Figurek Andreja , Luyckx Valerie , Hapuoja Laura , Schmid Daniel , Mueller Thomas 
Published: June 2023

Abstract

Background and Aims
Accurate assessment of renal function is of great importance in clinical practise, in particular in patients undergoing nephrectomy due to tumor nephrectomy or in potential living kidney donors. In both cases, residual renal function is dependent on the remaining nephron number and their function. A reliable prediction of the post-nephrectomy kidney function would be of great help to identify the patient with an increased functional risk. The aim of this study was to assess if the short-term kidney function after nephrectomy can be reliably predicted.

Method
We performed a retrospective study in 68 living kidney donors (LD-Nx) and 43 patients undergoing nephrectomy due to a renal tumour (Tu-Nx) between 1st of January 2011 to 31st of December 2015 at the University Hospital Zurich. Baseline serum creatinine was defined as lowest observed serum creatinine value before LD-Nx and Tu-Nx and was used for calculation of estimated glomerular filtration rate (eGFR) by the Cockroft-Gault (CG) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulas. The expected post-nephrectomy kidney function was calculated based on the formula (expected eGFRpost = 0.6 * eGFRpre + 8.7) described in detail in: (Prediction of kidney function after nephrectomy was performed by using the formulas previosly established by our group [1]). Expected eGFR was calculated for CG and CKD-EPI formulas and expected serum creatinine was calculated from the expected eGFR based on CG formula. The expected kidney function was then compared to the observed kdiney function based on lowest observed serum creatinine (LoObsSCr) during the first year after nephrectomy and the corresponding eGFR values for CG and CKD-EPI were calculated.

Results
Patients with nephrectomy due to renal tumour had significantly higher baseline serum creatinine levels compared to living donors (100±50 umol/l vs. 70±12 umol/l, respectively) with 35% having proteinuria, 58% hypertension and 14% diabetes mellitus. In addition Tu-Nx patients were significantly older and had a higher body weight. Living donors had a higher percentage of smokers (31%) compared to the other group. Predonation eGFR CKD-EPI was 71±23 ml/min/1.73 m2 for Tu-Nx and 94±12 ml/min/1.73 m2 for LD-Nx patients. Both groups showed an adaptive increase in kidney function calculated by eGFR CKD-EPI: 29% for Tu-Nx and 14% for LD-Nx. LD-Nx patients had less bias in prediction of post-nephrectomy kidney function (Table 1). Lowest observed serum creatinine after nephrectomy did not significantly differ between the groups. A significant correlation between expected and observed serum creatinine values, as well as between expected and observed eGFR post-nephrectomy, was seen in both groups of patients.

Conclusion
Despite older age, higher body weight and more comorbidities, patients with tumor nephrectomy show an adaptive increase in kidney function. Prediction of kidney function after nephrectomy is possible for both groups, however more accurate for living donor patients.