Dextranomer/hyaluronic acid (Deflux) has been widely used in the treatment of vesicoureteral reflux in the pediatric population. It has demonstrated acceptable early efficacy with minimal morbidity. Early complications from Deflux have been reported to occur in approximately 1% of cases. However, late complications from Deflux use, including calcification and delayed ureteral obstruction, are less well understood. We present the case of an asymptomatic 11 year old girl with severe ipsilateral hydroureteronephrosis, identified nearly 8 years after treatment. This case details a rare instance of loss of renal function after Deflux use in a patient with no apparent risk factors.