Purpose: This is the first report to compare 3-dimensional computed tomography (3D-CT) images between pediatric patients with enuresis and children without lower urinary tract symptoms who underwent pelvic CT for other reasons. Methods: Forty-seven children (33 boys and 14 girls) with primary enuresis underwent 3D-CT of sacrococcygeal bones. The control group consisted of 138 children (78 boys and 60 girls) who underwent pelvic CT for other reasons. First, we determined the presence or absence of unfused sacral arches at the L4-S3 levels in both cohorts. Subsequently, we compared the fusion of sacral arches in age- and sex-matched children from these 2 groups. Results: Dysplastic sacral arches, characterized by lack of fusion at 1 or more levels of the S1–3 arches, were observed in nearly all patients in the enuresis group. In the control group (n=138), 54 of 79 children over 10 years old (68%) exhibited fused sacral arches at 3 S1–3 levels. All 11 control children under 4 years old displayed at least 2 unfused sacral arches at the S1–3 levels. In a comparative study of age- and sex-matched patients with enuresis and control children aged 5 to 13 years (n=32 for each group, with 21 boys and 11 girls; mean age, 8.0±2.2 years [range, 5–13 years]), only 1 patient (3%) in the enuresis group exhibited fusion of all S1–3 arches. In contrast, 20 of 32 control group participants (63%) had 3 fused sacral arches (P<0.0001). Conclusions Sacral vertebral arches typically fuse by the age of 10 years. However, in this study, children with enuresis exhibited a significantly elevated prevalence of unfused sacral arches, suggesting that dysplastic development of sacral vertebral arches may play a pathological role in enuresis.