Real‐time estimation of nephron activity with a linear measurement system (RENAL‐MS) predicts postoperative estimated glomerular filtration rate

Abstract

IntroductionPreoperative nuclear medicine renal scintigraphy (NMRS) is often used to predict estimated glomerular filtration (eGFR) after nephrectomy by estimating preoperative split renal function. We sought to determine whether a simple point‐of‐care measurement system estimating renal parenchymal volume using tools ubiquitously available could be used to replace NMRS in current clinical practice.Materials/MethodsWe performed a retrospective review of patients who underwent abdominal cross‐sectional imaging (CT/MRI) and mercaptoacetyltriglycine nuclear medicine renal scintigraphy (NMRS) prior to total nephrectomy at a single institution. We developed the real‐time estimation of nephron activity with a linear measurement system (RENAL‐MS) method of estimating postoperative renal function via the following technique: renal parenchymal volume of the removed kidney relative to the remaining kidney was estimated as the product of renal length and the average of 6 renal parenchymal thickness measurements. The utility of this value was compared to the utility of the split renal function measured by MAG3 for prediction of eGFR and new onset CKDIII ≥90 days after nephrectomy using univariate and multivariate linear and logistic regression respectively.Results57 patients met study criteria. Median age was 69 (IQR 61‐80) years. Median preoperative and postoperative eGFR was 74 (IQR 57‐89) mL/min/1.73^2 and 46 (IQR 35‐62), respectively. Correlations between actual and predicted postoperative eGFR were similar whether RENAL‐MS and NMRS methods were used, with correlation using RENAL‐MS being slightly numerically but not statistically superior (R = 0.82 and 0.76; p=0.138). ROC analysis using logistic regression estimates incorporating age, sex, and preoperative creatinine to predict postoperative CKDIII were similar between RENAL‐MS and NMRS (AUC 0.95 vs. 0.98).ConclusionA point‐of‐care tool to estimate renal parenchymal volume (RENAL‐MS) performed equally well as NMRS to predict postoperative eGFR and de‐novo CKDIII after nephrectomy in our population, suggesting NMRS may not be necessary in this setting.