Oncology Preoperative Nuclear Renal Scan Underestimates Renal Function After Radical Nephrectomy Laurie Bachrach, Edris Negron, Joceline S. Liu, Yu-Kai Su, James J. Paparello, Scott Eggener, and Shilajit D. Kundu OBJECTIVE
METHODS RESULTS
CONCLUSION
To compare expected and actual renal function after nephrectomy. Nuclear renal scan estimates differential kidney function and is commonly used to calculate expected postoperative renal function after radical nephrectomy. However, the observed postoperative renal function is often different from the expected. A retrospective review was performed on 136 patients who underwent radical nephrectomy or nephroureterectomy and had a preoperative renal scan with calculated differential function. Glomerular filtration rate (GFR) values, preoperative and postoperative, were calculated with the Modification of Diet in Renal Disease (MDRD) equation. The expected postoperative GFR based on renal scan was compared with the actual postoperative GFR. The average age of patients undergoing surgery was 58.6 years, and the indication for surgery was for benign causes in 59 (44%) patients and cancer in 76 (56%) patients. The average preoperative creatinine and estimated GFR were 1.0 mg/dL and 69.9 mL/min/1.73 m2. At a median follow-up of 3.3 months, the actual postoperative GFR exceeded the expected GFR by an average of 12.1% (interquartile range, 2.6%-25.2%). When stratified by preoperative GFR >90, 60-90, and 64,000 new kidney cases were diagnosed, and the highest increase was observed in the incidence of localized tumors.3-5 Management options of patients with renal masses may include observation, ablation, partial nephrectomy, or radical nephrectomy.6 In counseling patients regarding the appropriate management decision, the risk of malignancy is weighed against the potential loss of renal function, which can range from new or worsening chronic kidney disease to dialysis-dependent renal failure. Approximately 30% of patients newly diagnosed with a renal mass have chronic kidney disease, defined as an estimated glomerular filtration rate (eGFR) 18 years and underwent surgery between 2001 and 2011. We identified 136 subjects who met the inclusion criteria. One patient was excluded due to repeat episodes of acute renal failure that resulted in wide variations in creatinine and hence an unreliable eGFR. Preoperative and postoperative eGFR values were calculated with the Modification of Diet in Renal Disease (MDRD) equation and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula using the calculations posted by the National Institute of Diabetes and Digestive and Kidney Diseases.11 MDRD was used in our final analysis. Expected postoperative eGFR was compared with the actual postoperative GFR by calculating the difference in the expected vs observed values as a percentage of the observed GFR. Demographic, operative, and pathologic data were analyzed to determine their association with differences in the expected vs observed renal function.
RESULTS Our subjects consisted of 64 (47%) men and 71 (53%) women, with a racial distribution representative of the region (Table 1). Within the cohort, 25 (18.5%) patients had diabetes, 69 (51.1%) hypertension, 38 (28.1%) hyperlipidemia, and 16 (11.9%) coronary artery disease. There were 20 (14.8%) active smokers at the time of surgery with a reported average of 22 packs per year history (interquartile range [IQR], 12-40 packs per year). The average age was 58.6 years (IQR, 49.9-68.2 years), and average body mass index was 29.3 kg/m2 (IQR, 24.8-35.5 kg/m2). Average preoperative creatinine and eGFR were 1.0 mg/dL (IQR, 0.8-1.2 mg/dL) and 69.9 mL/min/ 1.73 m2 (IQR, 54.8-82.0 mL/min/1.73 m2), respectively. On preoperative renal scan, the average differential percent function of the nonremoved kidney was 61% (IQR, 50.5%-82.5%). Postoperative renal function was estimated at an average of 99 days after surgery (IQR, 39170; Table 2). Average postoperative creatinine and GFR were 1.2 mg/dL (IQR, 1.1-1.5 mg/dL) and 52.6 mL/min/ 1.73 m2 (IQR, 42.6-62.9 mL/min/1.73 m2), respectively. Overall, the observed postoperative renal function was 12.1% (IQR, 2.6-25.2) higher than the expected. Differences in the expected vs observed renal function were most notable in patients with preoperative CKD. In patients with preoperative GFR >90, between 90 and 60, and 90 112.4 (93.1-112.5) 60-90 74.2 (69.2-79.2)
METHODS RESULTS
CONCLUSION
To compare expected and actual renal function after nephrectomy. Nuclear renal scan estimates differential kidney function and is commonly used to calculate expected postoperative renal function after radical nephrectomy. However, the observed postoperative renal function is often different from the expected. A retrospective review was performed on 136 patients who underwent radical nephrectomy or nephroureterectomy and had a preoperative renal scan with calculated differential function. Glomerular filtration rate (GFR) values, preoperative and postoperative, were calculated with the Modification of Diet in Renal Disease (MDRD) equation. The expected postoperative GFR based on renal scan was compared with the actual postoperative GFR. The average age of patients undergoing surgery was 58.6 years, and the indication for surgery was for benign causes in 59 (44%) patients and cancer in 76 (56%) patients. The average preoperative creatinine and estimated GFR were 1.0 mg/dL and 69.9 mL/min/1.73 m2. At a median follow-up of 3.3 months, the actual postoperative GFR exceeded the expected GFR by an average of 12.1% (interquartile range, 2.6%-25.2%). When stratified by preoperative GFR >90, 60-90, and 64,000 new kidney cases were diagnosed, and the highest increase was observed in the incidence of localized tumors.3-5 Management options of patients with renal masses may include observation, ablation, partial nephrectomy, or radical nephrectomy.6 In counseling patients regarding the appropriate management decision, the risk of malignancy is weighed against the potential loss of renal function, which can range from new or worsening chronic kidney disease to dialysis-dependent renal failure. Approximately 30% of patients newly diagnosed with a renal mass have chronic kidney disease, defined as an estimated glomerular filtration rate (eGFR) 18 years and underwent surgery between 2001 and 2011. We identified 136 subjects who met the inclusion criteria. One patient was excluded due to repeat episodes of acute renal failure that resulted in wide variations in creatinine and hence an unreliable eGFR. Preoperative and postoperative eGFR values were calculated with the Modification of Diet in Renal Disease (MDRD) equation and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula using the calculations posted by the National Institute of Diabetes and Digestive and Kidney Diseases.11 MDRD was used in our final analysis. Expected postoperative eGFR was compared with the actual postoperative GFR by calculating the difference in the expected vs observed values as a percentage of the observed GFR. Demographic, operative, and pathologic data were analyzed to determine their association with differences in the expected vs observed renal function.
RESULTS Our subjects consisted of 64 (47%) men and 71 (53%) women, with a racial distribution representative of the region (Table 1). Within the cohort, 25 (18.5%) patients had diabetes, 69 (51.1%) hypertension, 38 (28.1%) hyperlipidemia, and 16 (11.9%) coronary artery disease. There were 20 (14.8%) active smokers at the time of surgery with a reported average of 22 packs per year history (interquartile range [IQR], 12-40 packs per year). The average age was 58.6 years (IQR, 49.9-68.2 years), and average body mass index was 29.3 kg/m2 (IQR, 24.8-35.5 kg/m2). Average preoperative creatinine and eGFR were 1.0 mg/dL (IQR, 0.8-1.2 mg/dL) and 69.9 mL/min/ 1.73 m2 (IQR, 54.8-82.0 mL/min/1.73 m2), respectively. On preoperative renal scan, the average differential percent function of the nonremoved kidney was 61% (IQR, 50.5%-82.5%). Postoperative renal function was estimated at an average of 99 days after surgery (IQR, 39170; Table 2). Average postoperative creatinine and GFR were 1.2 mg/dL (IQR, 1.1-1.5 mg/dL) and 52.6 mL/min/ 1.73 m2 (IQR, 42.6-62.9 mL/min/1.73 m2), respectively. Overall, the observed postoperative renal function was 12.1% (IQR, 2.6-25.2) higher than the expected. Differences in the expected vs observed renal function were most notable in patients with preoperative CKD. In patients with preoperative GFR >90, between 90 and 60, and 90 112.4 (93.1-112.5) 60-90 74.2 (69.2-79.2)
