Diagnostic ultrasound ( PDFDrive )

CHAPTER
36
The Fetal Chest
Dorothy Bulas
SUMMARY OF KEY POINTS
• Normal fetal lungs appear homogeneously echogenic on
ultrasound surrounding the heart with a cardiothoracic ratio
that remains constant through the second and third
trimesters.
• Pulmonary hypoplasia can be primary or secondary and
unilateral or bilateral.
• Congenital pulmonary airway malformations (CPAMs) are a
spectrum of disorders that include bronchopulmonary
malformation, hybrid lesions (CPAM and sequestration),
and congenital lobar overinlation/bronchial atresia.
• A large fetal lung mass can compress and shift the heart
and vena cava, resulting in fetal hydrops.
• Congenital pulmonary airway malformation volume ratio
(CVR) is the CPAM volume divided by the head
circumference. A CVR of 1.6 or less without a dominant
cyst is considered low risk for the development of
hydrops.
• Congenital lobar overinlation (CLO) appears echogenic on
ultrasound and can involve a segment or subsegment of
lung. CLO accounts for up to 20% of prenatally diagnosed
fetal lung malformations.
• Congenital diaphragmatic hernias have a variable outcome
dependent on severity of lung hypoplasia, liver herniation,
and the presence of additional anomalies.
CHAPTER OUTLINE
DEVELOPMENT OF STRUCTURES IN
THE CHEST
Pulmonary Development
Normal Sonographic Features of the
Fetal Chest
Normal Diaphragm
Normal Thymus
PULMONARY HYPOPLASIA,
APLASIA, AND AGENESIS
CONGENITAL PULMONARY AIRWAY
MALFORMATION SPECTRUM
Congenital Pulmonary Airway
Malformation
Bronchopulmonary Sequestration
Congenital Lobar Overinlation
PLEUROPULMONARY
BLASTOMA
CONGENITAL HIGH AIRWAY
OBSTRUCTION
BRONCHOGENIC CYST
NEURENTERIC CYST
PLEURAL EFFUSION
PERICARDIAL EFFUSION
PULMONARY LYMPHANGIECTASIA
CONGENITAL DIAPHRAGMATIC
HERNIA
Other Hernias and Eventration
Associated Anomalies
Morbidity and Mortality
In Utero Therapy
CONCLUSION
Familiarity with the normal development of the fetal chest
is critical both for recognizing chest anomalies and for
understanding the consequences of these anomalies. Accurate
prenatal diagnosis of thoracic lesions is important in providing
appropriate recommendations for counseling, planning potential
in utero interventions, and determining the optimal mode of
delivery and postnatal care. Prenatal imaging can identify thoracic
lesions and assess their impact on mediastinal structures and
potential development of hydrops. Although chest abnormalities
may be associated with lethal pulmonary hypoplasia, fatal
chromosomal abnormalities, and lethal structural anomalies,
many chest lesions resolve in utero with minimal sequelae. Fetal
magnetic resonance imaging (MRI) can be a useful adjunct in
cases with unclear sonographic diagnosis or potential need for
in utero interventions.
DEVELOPMENT OF STRUCTURES IN
THE CHEST
Pulmonary Development
In the human lung, there are ive distinct stages of development,
during which the lung matures and the number of alveoli
increases. 1,2 At birth, the lungs are functional but structurally
immature; the greatest increase in number of alveoli occurs
postnatally. During the irst 3 years of life, the alveoli are formed
through a septation process that increases the gas exchange surface
area. It is important to understand that this lung development
process is ongoing, and that space-occupying lesions, or extrinsic
abnormalities that do not allow for normal lung growth, can
lead to improper lung development.
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