Background <p>Several studies have investigated long-term kidney outcomes in survivors of Wilms tumor (WT). However, many have small sample sizes, and there is a wide variation in reported outcomes. The aim of this study is to investigate the long-term kidney outcomes in survivors of WT (S-WT), including those patients considered to be at high risk for poor kidney outcomes, and using updated estimated glomerular filtration rate (eGFR) equations.</p> Methods <p>This was a retrospective chart review of 64 patients treated for WT at a single pediatric center. Patients were off treatment for 5&#xa0;years or more at the time of analysis and were evaluated for decreased kidney function, hypertension, proteinuria, and compensatory hypertrophy of the contralateral kidney.</p> Results <p>At a median follow-up time of 11.3&#xa0;years off treatment (range 5–22.6) and average age of 16.7&#xa0;years (range 6.5–30), 35 patients had a decreased eGFR (&lt; 90&#xa0;mL/min/1.73 m²), and 2 patients had progressed to chronic kidney disease stage 5. Compensatory hypertrophy was observed in 67% of cases. 41% of patients had elevated clinic blood pressures, with 2 patients on an anti-hypertensive medication. Three of 9 patients had evidence of hypertension on ambulatory blood pressure monitoring. Eight of 37 patients (22%) had proteinuria.</p> Conclusions <p>Kidney dysfunction is common in S-WT at a young age. This population should be carefully monitored for the development of decreased eGFR, hypertension, and proteinuria as part of their routine survivorship care. This is particularly true for modifiable risk factors of chronic kidney disease progression, such as hypertension and proteinuria.</p> Graphical Abstract <p></p>