Renal Deterioration Index: Preoperative Prognostic Model for Renal Functional Outcome After Treatment of Bilateral Obstructive Urolithiasis in Patients with Chronic Kidney Disease

Abstract

Patients who present with varying severity of obstructive urolithiasis behave differently after the treatment. Some patients recover with improved renal function while others progress to renal failure. Our objective was to objectively quantify which patients would progress to renal failure after treatment for obstructive urolithiasis. A prospective analysis of 167 patients with renal failure from bilateral obstructive urolithiasis who were treated and subsequently followed for at least 1 year was performed. Failure was defined as glomerular filtration rate (GFR) values less than 15 mL/min at 1 year follow-up. All patients had preoperative placement of a percutaneous nephrostomy tube for at least 5 days before treatment with either ureteroscopy or percutaneous nephrolithotomy. Multiple logistic regression analysis of affecting parameters was performed. A renal deterioration index (RDI) was constructed based on scores assigned to varying severity of multivariate significant factors and the receiver operating characteristic (ROC) curve was analyzed. There were 48(28.7%) patients who progressed to CKD stage V at 1-year follow-up. Combined cortical width (≤ 0.001), proteinuria (0.01), positive urine culture (0.004), and nadir preoperative GFR postbilateral percutaneous nephrostomy (0.016) were statistically significant factors affecting renal deterioration on multivariate analysis. RDI has a high ROC curve (AUC=0.90) for predicting renal functional outcome. Combining these parameters in a prediction table yielded a RDI score ≥ 12 being associated with high odds risk (odds ratio=11.2) of treatment failure. RDI ≥ 12 is associated with renal deterioration after appropriate treatment of bilateral obstructive urolithiasis.