Tailgut cyst: diagnosis with CT and sonography.

Tailgut cyst is a rare congenital lesion that presents as a presacral mass, found in infancy or persisting undetected into adulthood, and characterized by multiple cysts lined with a gastrointestinal type of epithelium. In a retrospective review of five patients whose ages ranged from 1 month to 42 years--three cases with CT and two with sonograms--tailgut cyst appeared as a complex mass on both procedures, representing its composition of multiple small cysts filled with keratinous material and other debris. Other CT and sonographic features include well-defined borders, and, in one case, presentation as a mass lateral to the midline. CT also shows preservation of adjacent fat planes. Tailgut cyst should be included in the differential diagnosis of a retrorectal mass at any age.