A pseudosinus tract is a normal fibrous cord extending from the coccyx to an overlying sacral dimple. These have no associated mass and contain no fluid (if CSF drainage is occurring via the sacral dimple, then a true dorsal dermal sinus should be considered).
Diagnosis
Ultrasound
Hypoechoic cordlike region extending from a skin dimple to the tip of the coccyx, with no internal fluid or associated mass.
MRI
T1/T2 hypointense band extending from a skin dimple to the tip of the coccyx, with no internal fluid or associated mass.
Differential diagnosis
- sacral dimple
- dorsal dermal sinus - true dorsal dermal sinuses are typically in a more cranial location, rarely at the tip of the coccyx
- pilonidal sinus