fetale Megazystis

Fetal megacystis refers to the presence of an unusually large bladder in a fetus.


The estimated incidence of antenatal imaging is at ~1:1500 pregnancies.


It can result from a number of causes but the main underlying mechanism is either distal stenosis or reflux.


Associated anomalies are common and include:

Radiographic assessment

Antenatal ultrasound

It is generally defined as:

  • bladder diameter >7 mm in the first trimester
  • bladder diameter >30 mm in the second trimester
  • bladder diameter >60 mm in the third trimester
Ancillary sonographic findings

Treatment and prognosis

The overall prognosis can be variable from progressive obstruction to spontaneous resolution. A follow-up ultrasound is necessary to correctly interpret the significance of megacystis detected in the first trimester.

If the fetus is chromosomally normal and there is megacystis on the 1 trimester scan:

  • there is a spontaneous resolution of the megacystis in about 90% of cases when the 1 trimester longitudinal bladder diameter is between 7-15 mm
  • if the bladder diameter is >15 mm, there is a very high likelihood of progressive obstructive uropathy

Management will depend on the underlying pathology.

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