Preoperative radiographic parameters predict long-term renal impairment following partial nephrectomy

Purpose: We analyzed radiographic parameters describing anatomic features of renal tumors to identify preoperative characteristics that could help predict long-term decline in renal function following partial nephrectomy. Methods: We retrospectively reviewed the records of 194 consecutive patients who underwent partial nephrectomy from January 2006 to March 2009 and analyzed a cohort of 53 patients for whom complete clinical, radiographic, and operative information was available. Computed tomography images were reviewed by a single radiologist. Radiographic criteria for describing renal tumor size and location included diameter, volume, endophytic properties, proximity to collecting system, anterior/posterior location, location relative to polar lines, and R.E.N.A.L. nephrometry score. Postoperative estimated glomerular filtration rate was calculated using the MDRD study group equation with serum creatinine at last follow-up. Results: The median preoperative and postoperative GFR values were 75 (IQR 65-97) and 66 (IQR 55-84) mL/min/1.73 m², respectively. At a median follow-up of 38 months, the median percentage decrease in GFR was 12%. On univariate analyses, tumor diameter (P = 0.002), tumor volume (P < 0.0001), nearness of tumor to collecting system (P = 0.017), and location relative to polar lines (P = 0.017) were associated with percentage decrease in GFR. Furthermore, higher R.E.N.A.L. nephrometry score was also associated with poorer renal functional outcomes following partial nephrectomy (P = 0.019). Conclusions: Anatomic features of renal tumors defined by preoperative radiographic characteristics correlate with the degree of renal functional decline after partial nephrectomy. Identification of these parameters may assist in patient counseling and clinical decision making following partial nephrectomy. Validation in larger prospective studies is necessary.