ABSTRACT

In the first trimester, an enlarged bladder 7 mm (megacystis) should raise the suspicion of either chromosomal abnormalities or obstructive uropathy. Approximately 20% of fetuses with megacystis measuring 7-15 mm have an underlying chromosomal abnormality such as trisomy 13 or 18. If the bladder measures 15 mm, the risk of an underlying bladder outlet obstruction (urethral atresia, posterior urethral valves, or cloacal abnormalities) is very high and is associated with a very poor prognosis. With megacystis 15 mm, it is sometimes possible to find echogenic or dysplastic kidneys and reduced liquor volume in the first trimester.