Fetal ovarian cysts: review of imaging spectrum, differential diagnosis, management, and outcome.

Fetal ovarian cysts are the most common abdominal cysts observed in the female fetus but may be mistaken for genitourinary cysts, gastrointestinal cysts, lymphangiomas, or fetus in fetu. Ultrasonography (US) is the imaging modality of choice for fetal assessment, and magnetic resonance imaging is a useful problem-solving tool when uncertainty remains after careful US evaluation. At US, a fetal ovarian cyst manifests as an anechoic thin-walled cyst superior and parasagittal to the bladder. A daughter cyst may occasionally be observed and is pathognomonic for a cyst of ovarian origin. Fetal ovarian cysts may be simple or complicated and unilateral or bilateral, and they may masquerade as a solid mass when hemorrhage or torsion occurs. Complicated cysts may exhibit multiple septations, fluid-fluid levels, or mobile internal echoes. It is important to differentiate a hemorrhagic ovarian cyst from solid abdominal neoplasms that may be seen in a fetus. Recognition of the pertinent imaging findings will help radiologists distinguish fetal ovarian cysts from other fetal intra-abdominal masses in the differential diagnosis. Malignant ovarian neoplasms are rare in the fetus and neonate and thus are not considered in the differential diagnosis. The current literature on the management and outcome of fetal ovarian cysts is reviewed, with imaging studies presented from the authors' practice. Most fetal ovarian cysts resolve spontaneously; if operative intervention is required, the goal should be ovarian preservation.