Imaging in sacrococcygeal teratoma

quote from "Pediatric Surgery (Springer Surgery Atlas)" by Prem Puri, Michael E. Höllwarth -

"An abdominal ultrasound will determine the size and consistency of any pelvic or abdominal component. It may be necessary to fill the bladder with water to allow it to be used as a sonic window. MRI should clearly distinguish between sacrococcygeal teratoma and anterior meningocele, and may be able to detect the occasional extension of the tumour through the sacral hiatus into the spinal canal."