·Adrenal hemorrhage- More common perinatally but has been reported in utero as an anechoic mass showing spontaneous regression over time. Eventually a normal sized adrenal gland with a rim of calcification may remain in the infant.
·Simple adrenal cysts- These have been reported as well defined anechoic masses resolving spontaneously in the early neonatal period. There was no associated mass or calcification.
·Adrenal cyst mimics- Renal cysts, hydronephrotic upper moiety of a duplex renal system and necrotic Wilms’ tumor may mimic adrenal cysts. A postnatal follow up sonogram should resolve the issue.
·Adrenal neuroblastoma- The tumor is more often complex with cystic and solid components, although a completely cystic adrenal mass has been documented.
·Other adrenal cysts- These may be lymphangiomatous, angiomatous retention cysts or cysts within an adenoma. They do not involute spontaneously. These cysts have been noted in infants but have not been reported in utero.
·Nuroblastoma in situ- This is a benign lesion said to occur in 1.5% of normal newborns. The mass may occur in the fetus and is more commonly solid or complex rather than cystic. The lesion either resolves spontaneously or matures into normal adrenal tissue, Usually microscopic and therefore not seen.