Occult anterior sacral meningocele.

Anterior sacral meningocele is a rare congenital malformation consisting of a spinal fluid-filled sac in the pelvis communicating by a small neck with the spinal subarachnoid space through a sacral defect. This entity should be considered if the characteristic scimitar sacrum is observed on a pelvic roentgenogram. If signs and symptoms also suggest a meningocele, special studies such as ultrasonography and myelography are indicated to establish the diagnosis of an anterior sacral meningocele. Computerized tomography provides additional evidence of spinal-abdominal extension of this lesion.