Sacral agenesis: why is it so frequently misdiagnosed?

Thirty-four patients with sacral agenesis were seen from 1954 to 1983, cases of meningomyelocele excluded. Five recognizable and consistent patterns of bone malformation were identified. Urodynamic examinations were done in 10 of the 34 patients. Their evaluation and response to treatment are analyzed; we tried to determine and establish the possible causes for its late diagnosis and consequences regarding the upper urinary tract.