Diagnostic ultrasound ( PDFDrive )

CHAPTER 36 The Fetal Chest 1255
central nervous system. At times, CHAOS is in association with
a tracheoesophageal istula. his istula acts as an alternative
pathway for the accumulated luid, leading to a decrease in lung
volume, reversal of diaphragmatic eversion, and resolution of
ascites and polyhydramnios. 108
If untreated, laryngeal and tracheal atresia can lead to death
either in utero from hydrops or within minutes ater birth from
respiratory compromise. Neonatal survival is possible if the
delivery is performed with the ex utero intrapartum treatment
(EXIT) procedure. 121-124 he EXIT procedure involves tracheostomy
placement below the level of the obstruction while maternal
placental circulation is maintained.
BRONCHOGENIC CYST
Bronchogenic cysts (Table 36.4) are rare anomalies that result
from abnormal budding or branching of the tracheobronchial
tree. hey are most oten located in the mediastinum in the
subcarinal region. 125 However, 15% of bronchogenic cysts occur
in the lungs, pleura, and diaphragm. hey account for 11% to
18% of mediastinal masses in infants and children. 126,127 he cyst
is lined by ciliated mucus-secreting bronchial epithelium and
may be mucus-illed. Although the mediastinal cysts do not
communicate with the bronchopulmonary tree, intrapulmonary
cysts usually do.
Bronchogenic cysts range in size from a few millimeters to
more than 5 cm. On prenatal ultrasound, they usually appear
as anechoic unilocular intrathoracic cysts (Fig. 36.9), at times
with layering echogenic material. 128,129 If the cyst does not cause
mass efect, it typically will not cause a problem in utero. However,
if the cyst compresses the airway, it can lead to airway obstruction
at birth. 130 he main diferential diagnosis is CPAM. However,
CPAM usually has more than one cyst and an associated echogenic
mass with mass efect. If a bronchogenic cyst causes obstruction,
it may lead to the distal lung accumulating luid, masquerading
as an echogenic lung lesion such as CPAM or sequestration.
he cyst can be mediastinal or parenchymal. Mediastinal
lesions are typically unilocular, located midline in the subcarinal
region (75%). Parenchymal lesions are usually simple unilocular
cysts located along the tracheobronchial tree. Septations may be
seen. At times the cyst can cause bronchial compression and
result in distal overinlation.
Fetal MRI can be helpful in cases with an unclear diagnosis.
he cyst exhibits high signal intensity on T2-weighted imaging.
When the cyst causes obstruction, there will be distal lung
overinlation, and the lung will become hyperintense as well. 130
Surgical resection for bronchogenic cysts is performed postnatally
TABLE 36.4 Differential
Diagnosis of Fetal Thoracic
Cystic Lesion
Congenital pulmonary
airway malformation
(CPAM)
Congenital diaphragmatic
hernia (CDH)
Teratoma
Neurenteric cyst
Bronchogenic cyst
Esophageal duplication
Lymphangioma
Distinguishing Features
Associated with echogenic
lung mass, typically
multiple cysts
Peristalsis of bowel in chest
Stomach above diaphragm
Absence of part of the
diaphragm
Mass does not obey lobar
boundaries; may have
calciications
Adjacent to spine
Typically single cyst, may
obstruct and have distal
hyperinlated lung
Adjacent to esophagus
Crosses anatomic boundaries
A
B
FIG. 36.9 Bronchogenic Cyst at 23 Weeks. (A) Axial gray-scale and (B) sagittal color Doppler ultrasound images of the chest demonstrate a
simple cyst (arrow) posterior to the heart.