Renal Function of Patients With Synchronous Bilateral Wilms Tumor

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To the Editor:
We read with great interest the important paper recently published by Davidoff et al1 in Annals of Surgery. The authors reviewed their institutional experience with nephron-sparing surgery in 42 children with synchronous bilateral Wilms tumor. The most important finding was that nephron-sparing surgery was feasible in nearly all patients. At mean follow-up of 4.1 years, the overall survival rate was 85.7%. At a median age of 6.7 years at follow-up, 11 patients (30%) were on antihypertensive medication. In addition, 2 patients had persistent systolic or diastolic blood pressure values above the 95th percentile for their age. Thirteen patients (36%) presented with an estimated glomerular filtration rate (eGFR) between 60 and 90 mL/min/1.72 m2.
The authors should be commended for these excellent results. However, in our opinion, the renal function results are not reassuring. During the last 15 years, several population studies have provided evidence that a low eGFR is associated with an increased morbidity and mortality risk. A meta-analysis of these studies concluded that an eGFR < 90 mL/min/1.73m2 is associated with a 20% to 30% increase in the risk of major cardiovascular events and death from any cause at the age of 70 years.2 Furthermore, 2 studies provided evidence that not only medical causes but also nephrectomy for kidney donation is associated with an increased risk for cardiovascular disease, overall mortality, and end-stage renal disease.3,4
Children in comparison with adults present an additional factor influencing renal function outcome. Two previous cross-sectional studies of renal function5,6 have shown that children who underwent ablation of 50% of renal mass for oncological and nononcological causes present after the age of 30 years a significant decline in renal function. The rate of decline of approximately 1.5 mL/min/1.73 m2/year was associated with a significant increase in blood pressure and albumin excretion.5 Similarly, the oldest Wilms tumor survivors (median age 56 years) presented a significant association between nephrectomy and blood pressure hypertension, a risk factor for chronic kidney disease.7 Interestingly, in an earlier paper survivors from the same cohort at median age of 29 years did not show an increased risk of hypertension.8
These findings have been confirmed by 2 longitudinal studies of renal function in children who underwent nephrectomy for unilateral renal tumor. Mulder et al9 found that children who underwent nephrectomy, in comparison with children who were not treated with nephrotoxic therapy, presented a lower eGFR (nephrectomy effect: P < 0.001) and an increasing renal dysfunction probability with longer follow-up (nephrectomy by time effect: P < 0.002). Similarly, Cozzi et al10 found that children who underwent nephrectomy for unilateral renal tumor showed a significant decrease in eGFR at a follow-up up to the fifth decade of life.
These data on renal function in children who underwent ablation of 50% of renal mass induce to believe that, in children with bilateral Wilms tumor, the amount of renal mass saved is of paramount importance. Therefore, conventional clamping of renal vessels to decrease blood loss should be avoided and hemostasis obtained by compression of renal parenchyma. In addition, a liberal use of tumor enucleation may serve to spare more functioning renal tissue.
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