Comprehensive renal function evaluation in patients treated for synchronous bilateral Wilms tumor

Objectives The purpose of this study was to perform a comprehensive assessment of long-term renal function in patients treated at our institution for synchronous bilateral Wilms tumor (BWT) and to determine the optimal method for estimating glomerular filtration rate (eGFR). Methods Surgical approach, adjuvant therapy, and pathology reports were reviewed for patients with at least six months follow-up from definitive surgery. eGFRs, as assessed by the Schwartz and Chronic Kidney Disease in Children (CKiD) formulas, were compared to measured GFR (mGFR) determined by ^99mTc-DTPA scanning. Urine studies, including microalbumin, β-microglobulin, and FE_Na were also reviewed. Results Forty-two patients were identified. Of 36 living patients, 28 (77.8%) had greater than 6 months follow-up, with a median overall follow-up of 5.2 years (range: 1.4–13.4). The median mGFR was 97 mL/min/1.73 m², while the median eGFR_Schwartz and eGFR_CKiD were 103.3 mL/min/1.73 m² and 79.7 mL/min/1.73 m², respectively, (p = 0.13 and p = 0.75, compared to mGFR). Eleven (39.3%) patients had at least one abnormal urine study (microalbumin > 30 μg/g creatinine, n = 3; β-2 microglobulin > 133 μg/g creatinine, n = 9; FE_Na > 1%, n = 4). Conclusions In our series, few patients had an abnormally low GFR. Neither method for estimating GFR gave a significantly different result from measured GFR, suggesting that the Schwartz equation is adequate, although specific urine tests may be more sensitive for detecting subtle renal dysfunction. Level of evidence Level IV — retrospective case series with no comparison group.