Fetal megacystis: differential diagnosis

Area of Science:

• Fetal Medicine
• Diagnostic Imaging
• Medical Genetics

Background:

• Fetal megacystis, characterized by an enlarged fetal bladder, presents diagnostic challenges.
• Accurate prenatal diagnosis is crucial for appropriate management and counseling.
• Distinguishing between various causes of fetal megacystis is essential for prognosis.

Purpose of the Study:

• To evaluate the utility of sonographic characteristics in diagnosing fetal megacystic bladders.
• To determine if specific sonographic findings can reliably differentiate between various fetal conditions causing megacystis.

Main Methods:

• Retrospective observational study of 20 fetuses with megacystis over a 10-year period.
• Analysis of sonographic records, including 2D, 3D/4D sonography, and advanced imaging techniques.
• Key sonographic features assessed: keyhole sign, bladder thickness, amniotic fluid index, and fetal sex.

Main Results:

• Seventeen male fetuses, 2 female, and 1 with ambiguous genitalia were identified.
• All male fetuses initially diagnosed with prune belly syndrome showed specific findings.
• The keyhole sign in male fetuses led to a revised diagnosis of megacystis secondary to posterior urethral valves in 10 cases.

Conclusions:

• Sonographic evaluation, particularly detailed fetal anatomic surveys using 2D and 3D/4D techniques, is effective in diagnosing fetal megacystis.
• Specific sonographic markers can reliably differentiate between prune belly syndrome, posterior urethral valves, urethral atresia, and megacystis-microcolon-intestinal hypoperistalsis syndrome.
• This approach aids in establishing the most likely diagnosis for fetuses with megacystic bladders.