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BACKGROUND:Partial Nephrectomy has been associated with greater preservation of renal function than radical nephrectomy. We sought to identify predictors of a significant decrease in postoperative estimated Glomerular Filtration Rate (eGFR) in patients undergoing Robotic Partial Nephrectomy (RPN) at a single institution.
METHODS:Retrospective review of an IRB approved institutional partial nephrectomy database. Patients who underwent RPN and had 6-12 month postoperative eGFR data were included in the study cohort. Variables analyzed included age, gender, body mass index (BMI), preoperative eGFR (calculated utilizing the Modification of Diet in Renal Disease formula), Charlson Comorbidity Index (CCI), tumor size, warm ischemia time (WIT) and estimated blood loss (EBL). Change in eGFR values (measured in mL/Min/1.73m²) 6-12 months after surgery were studied with mixed model linear regression and analysis of covariance. Change in Kidney Disease Outcomes Quality Initiative (KDOQI) Chronic Kidney Disease (CKD) classification stage was studied using Chi-squared tests.
RESULTS:128 patients (88 male/40 female) met inclusion criteria. Mean tumor size was 3.1±1.4 cm (range 0.8-8.5), mean age was 62±11 years, and mean CCI score was 4.8±1.9. Mean BMI was 29.4±5.2 kg/m² (19.6-46.8), mean WIT was 26±10 min (7-63) and mean EBL was 204mL (e^5.32). Pathology showed clear cell carcinoma in 60% of masses. The mean pre-op eGFR was 75.7±20.
Groups with greater (p<0.01) eGFR decline at 12 months on univariate analysis were age > 60 (27.34 vs. 9.24), BMI > 30 (8.3 vs. 1.8), EBL > 200 (12.35 vs. 1.85), CCI > 5 (14.8 vs. 1.6) and tumor size > 4 cm (4.4 vs. 2). Each minute of WIT > 21 min resulted in a decline in eGFR of 3.5 at 12 months. On multivariate analysis only age > 60 and WIT > 21 min were significantly associated with faster eGFR decline (p<0.01). Non-significant variables included clear cell pathology (p=0.15), and gender (p=0.09). Risk factors for change in renal function as quantified by an increase in KDOQI-CKD classification stage were analyzed separately. 51 patients(40%) experienced an increase in CKD stage (17 patients: stage 1-2, 1 patient: stage 1-3, 18 patients: stage 2-3, 4 patients: stage 2-4, 3 patients: stage 3-4, 2 patients: stage 4-5). Of the risk factors, only age > 60 was significantly predictive of an increase in CKD stage (p=0.015).
CONCLUSIONS:Patient age > 60, BMI > 30, EBL > 200 cc, WIT > 21 min and tumor size > 4 cm were predictive of decreased eGFR after RPN, with age and WIT persisting as predictive on multivariate analysis. Older patients undergoing RPN were also at greater risk for increases in KDOQI-CKD stage.