The sonographic appearance of an ovarian cyst is variable, depending on its size or complications, such as hemorrhage or torsion. An uncomplicated ovarian cyst appears as a unilocular cystic lesion and is usually localized to the pelvis or lower abdomen. When the cyst undergoes torsion or hemorrhages inside, the appearance may be complex or even solid 15,16 . Differential diagnosis Table 2 shows the differential diagnoses for a cystic mass. The differential diagnoses include urachal and mesenteric cysts or enteric duplication cyst, duodenal atresia, and dilated bowel 15 .
Urachal cysts are single and anterior, extending from the bladder to the umbilicus.
Differential diagnosis of abdominal cystic structures. The majority of ovarian cysts undergo spontaneous regression and involution following delivery or even in utero. Birth dystocia and respiratory distress have been reported from very large cysts 8 . To avoid potential complications, such as torsion and hemorrhage, antenatal percutaneous aspiration of ovarian cysts has been suggested. In the newborn, large cysts may cause ascites, they may undergo torsion, infarction, and may lead to intestinal obstruction by membranous adhesions, rupture or bleed.