Diagnostic ultrasound ( PDFDrive )

1246 PART IV Obstetric and Fetal Sonography
Prognosis and management are variable and depend on the
severity of the hypoplasia, age at delivery, and nature of the
associated conditions. Absence of fetal breathing movements in
the setting of oligohydramnios in pregnancies resulting from
premature rupture of membranes is a predictor for pulmonary
hypoplasia. 4 he spectrum of clinical outcomes ranges from mild
respiratory insuiciency to neonatal death.
In cases of unilateral pulmonary hypoplasia or aplasia, there
is mediastinal shit to the side of the hypoplastic lung, with no
associated mass in the contralateral lung to explain the degree
of mediastinal shit 33 (Fig. 36.3). he contralateral lung may be
enlarged and echogenic. 21 Pulmonary hypoplasia can also be
secondary to space-occupying lesions, such as congenital pulmonary
airway malformations (CPAMs), diaphragmatic hernia
(CDH), or pleural efusion.
FIG. 36.2 Secondary Pulmonary Hypoplasia in Fetus With
Thanatophoric Dysplasia. Transverse sonogram of the fetal chest at
20 weeks’ gestation demonstrates a small chest circumference secondary
to abnormally short ribs in this fetus with thanatophoric dysplasia.
TABLE 36.1 Causes of Pulmonary
Hypoplasia
Main Category
Primary pulmonary
hypoplasia or aplasia
Thoracic space-occupying
process
Oligohydramnios
Skeletal anomalies
Abnormal breathing
Chromosomal anomalies
and syndromes
Examples
Developmental abnormality
Congenital diaphragmatic
hernia
Lung masses
Mediastinal mass
Large pleural effusions
Bilateral renal agenesis
Prolonged preterm rupture
of membranes
Skeletal dysplasias
Chest wall tumors
Phrenic nerve abnormalities,
neuromuscular and central
nervous system
abnormalities
Trisomy 13, 18, and 21
Prenatal prediction of pulmonary hypoplasia and the degree
of severity are important for parental counseling as well as for
postnatal management planning, particularly if intensive respiratory
care is required immediately ater birth. 23 Proposed methods
for prediction of prenatal pulmonary hypoplasia 24 include estimation
of lung volumes by three-dimensional ultrasound 25,26 or by
MRI, 27 thoracic circumference 28,29 (Table 36.2), 30 lung-to-head
ratio, 9,31 lung-to-body weight ratio, 23 and Doppler studies of
pulmonary arteries. 32
CONGENITAL PULMONARY AIRWAY
MALFORMATION SPECTRUM
An echogenic lesion in the fetal thorax (Table 36.3) or a cystic
lesion in the fetal thorax can be part of the CPAM spectrum.
his spectrum includes lesions that have been historically called
congenital cystic adenomatoid malformation (CCAM), bronchopulmonary
sequestration (BPS), and congenital lobar
emphysema. CPAM is a congenital hamartomatous lung lesion
that communicates with the bronchial tree through an abnormal
communication and has normal pulmonary blood supply and
venous drainage into the pulmonary veins. 34 BPS is normally
developed lung tissue with systemic circulation. However, CPAM
and BPS lesions oten occur together and are then call hybrid
lesions or part of the CPAM spectrum. 35-37 For clarity, we will
describe these lesions separately, but the reader should be aware
that careful histologic inspection will oten ind regions of CPAM
in what appears to be a sequestration, as well as lesions that
resemble a CPAM that have both pulmonic and systemic feeding
vessels. Both of these types of lesions can have air trapping
postnatally and therefore may have elements of congenital lobar
overinlation (CLO; previously known as congenital lobar
emphysema).
Congenital Pulmonary
Airway Malformation
CPAM accounts for about 25% of congenital lung masses, 38 with
an incidence of 1 in 25,000 live births. 39 It is comprised of
pulmonary tissue with abnormal bronchial proliferation that
may involve either lung or any lobe. In 85% to 95% of cases,
CPAM is limited to one lobe or segment, with 2% to 3% of
CPAMs occurring bilaterally and with the right and let lungs
equally afected. 40
CPAM results from a pulmonary insult during embryologic
development of the bronchial tree before the seventh week of
gestation, resulting in failure of bronchial maturation and lack
of normal alveoli. Histologically, CPAM is diferentiated from
other lung masses by the absence of bronchial cartilage and
bronchial tubular glands, with overproduction of terminal