1460 FUNCTION PRESERVED IN THE OPERATED KIDNEY AFTER CONVENTIONAL PARTIAL NEPHRECTOMY IS DIRECTLY RELATED TO PARENCHYMAL VOLUME PRESERVATION

Abstract

INTRODUCTION AND OBJECTIVES: Ultimate decline in GFR after partial nephrectomy (PN) is influenced primarily by type and duration of ischemia and parenchymal volume preserved. The role of ischemia relative to volume preservation has been controversial. OBJECTIVES: To directly evaluate the function specifically in the operated kidney pre and post conventional PN and to assess relationships with type and duration of ischemia and percent parenchymal volume preserved. METHODS: 55 patients with localized renal tumors (2007-11) had necessary studies for analysis; there were no exclusions. This comprised 24 solitary kidneys and 31 bilateral kidneys with pre and post-operative RFS, and the analysis was exclusively focused on the operated kidney. 33 (60%) cases were open and the remainder were MIS. 24 cases (44%) utilized hypothermia and 31 were performed using limited warm ischemia. Volumetric CT scans were utilized to directly measure the volume of functional parenchyma pre (subtracting out the tumor) and post PN in the operated kidney. eGFR in the operated was determined by the MDRD2 equation, along with RFS data for patients with bilateral kidneys. Regression analysis was used to assess the relationships between ultimate GFR preserved in the operated kidney and potential predictive factors. All postoperative analyses were performed between 6-12 months. RESULTS: Median age was 61 years, median tumor size was 3.5 cm, and median RENAL score was 8. Median cold ischemia time (CIT) was 29 min (IQR 23-33) and median warm ischemia time (WIT) was 21 min (IQR 14.25-27.75). Pathology results showed pT1a in 33 (61.1%) and clear cell carcinoma in 41 (74.5%). Median preop GFR in the operated kidney was 47.2 (33.85-56) compared with 36.1 (25.0547.85) postoperatively. Median percent GFR preserved in the operated kidney was 88 (79-95.1). Median percent volume preserved was 83% (75.3-90.5). On regression analysis, percent GFR saved associated most strongly with percent parenchymal preservation (p 0.0001), but also with lower RENAL score (p 0.0174), and marginally with cold ischemia (p 0.0608). In contrast, length of ischemia did not correlate with percent GFR preserved (p 0.2487). Interestingly, function in the contralateral kidney did not change substantially ( 5% in all cases). CONCLUSIONS: Ultimate function after PN primarily correlated with parenchymal volume preservation, while ischemia played a secondary role. Thus, maximal parenchymal preservation with a precise PN should be a priority during conventional PN.