fetal megacystis

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

Epidemiology

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

Pathology

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

Associations

Associated anomalies are common and include:

• posterior urethral valves
• chromosomal anomalies
  • on a first trimester scan (10-14 weeks)
    • if the longitudinal bladder diameter is 7-15 mm, the risk of chromosomal defects is estimated at ~25%
    • if the bladder diameter is >15 mm, the risk of chromosomal defects is estimated at ~10%
• oligohydramnios
• megacystis microcolon intestinal hypoperistalsis (MMIH) syndrome (Berdon syndrome)
• megacystis megaureter syndrome
• prune belly syndrome

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

• may show evidence of oligohydramnios
• may show associated renal anomalies

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.

Siehe auch:

• Oligohydramnion
• prune belly syndrome
• chromosomale Anomalien
• Urethralklappe
• fetale intraabdominelle Zysten
• renal anomalies
• megacystis megaureter syndrome
• megacystis microcolon intenstinal hypoperistalsis syndrome

und weiter:

• obstetric curriculum
• fetal urinary ascites