We determined the cause of renal deterioration after augmentation cystoplasty (AC). Twenty-nine adult patients with refractory bladder dysfunction and who underwent ileocystoplasty from 2004 to 2015 were studied. Patients with a decline in glomerular filtration rate (GFR) after augmentation were reviewed. The primary outcome was to determine the factors that might lead to deterioration of estimated GFR. Median follow-up was 7.0 ± 2.6 years. Significant bladder capacity, end filling pressure, and bladder compliance were achieved from median 114 ± 53.6 to 342.1 ± 68.3 ml (p = .0001), 68.5 ± 19.9 to 28.2 ± 6.9 cm H2O (p = .0001), and 3.0 ± 2.1 to 12.8 ± 3.9 (p = .0001), respectively. Renal function remained stable and improved in 22 (76%) patients from median eGFR 135 ± 81.98 to 142.82 ± 94.4 ml/min/1.73 m2 (p = .160). Significant deterioration was found in 7 (24%) patients from median eGFR 68.25 ± 42 to 36.57 ± 35.33 (p = .001). The causes of renal deterioration were noncompliance to self-catheterization (2 patients), posterior urethral valve/dysplastic kidneys (2 patients), and reflux/infection (2 patients). On multivariate analysis, recurrent pyelonephritis (OR 3.87, p = 0.0155) and noncompliance (OR 30.78, p = 0.0156) were significant. We concluded that AC is not the cause of progression to end-stage renal disease in patients with renal insufficiency.