Wavy Floating Greater Omentum Findings Are Useful for Differentiating the Etiology of Fetal Ascites

The greater omentum is an apron-like peritoneal mesothelial sheet that was described by ultrasound as a floating fluid-filled viscus in ascites during the fetal period. To examine the association between the etiology of fetal ascites and ultrasound findings of the greater omentum, a retrospective study was conducted. Ultrasound findings of fetal omentum were defined as follows: (1) a cyst-like shape with a thin membrane observed as wavy in the ascites, (2) beside the stomach and below the liver, and (3) no blood flow noted on color Doppler. Eleven pregnancies had fetal ascites. A fetal greater omentum was confirmed in eight cases in which ascites were caused by non-peritonitis: fetal hydrops (n = 4), congenital cytomegalovirus infection (n = 2), idiopathic chylous ascites (n = 1), and unknown cause (n = 1). Of these eight cases, no abdominal surgical management was required in three live babies. However, a fetal greater omentum was not confirmed in all three cases of meconium peritonitis. It was suggested that the finding of the greater omentum can be an important clue for estimating the pathophysiological etiology of fetal ascites and helping with postnatal management. It should be reasonable to add the finding of the greater omentum to the detailed ultrasound examination checklist.