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Chapter 36 ■ The Fetal Chest 1277
(CPAM) spectrum. This spectrum includes lesions that
have been historically called congenital cystic adeno-
matoid malformation, bronchopulmonary sequestration, and congenital lobar emphysema. CCAM is a
congenital hamartomatous lung lesion,
35
and sequestration is normally developed lung tissue with systemic
circulation. However, these lesions often occur
together.
36-38
For clarity, we describe these lesions separately, but the reader should be aware that careful histologic inspection will often find regions of CCAM in
what appears to be a sequestration, as well as lesions that
resemble a CCAM that often have both pulmonic and
systemic feeding vessels. Both of these types of lesions
TABLE 36-2. CAUSES OF
PULMONARY HYPOPLASIA
PRIMARY
PULMONARY
HYPOPLASIA OR
APLASIA
Thoracic space-occupying
process
Oligohydramnios Bilateral renal agenesis
Skeletal and neural
malformations
Chromosomal anomalies
and syndromes
CCAM, Congenital cystic adenomatoid malformation; CNS, central nervous
system.
DEVELOPMENTAL
ABNORMALITY
Congenital diaphragmatic hernia
(CDH)
Congenital lung masses such as
CCAM, sequestration, and
bronchogenic cyst
Mediastinal mass: cardiac masses
such as teratomas (rare)
Large pleural effusions
Prolonged preterm rupture of
membranes
Skeletal dysplasias such as
thanatotropic dysplasia or
osteogenesis imperfecta
Chest wall tumors
Phrenic nerve abnormalities
Neuromuscular and CNS anomalies
Trisomies 13, 18, and 21
Robert syndrome
can have air trapping postnatally and therefore may have
elements of congenital lobar emphysema.
Congenital Cystic Adenomatoid
Malformation
Congenital cystic adenomatoid malformation accounts
for about 25% of congenital lung masses,
incidence of 1 in 25,000 live births.
40
It is comprised of
39
with an
pulmonary tissue with abnormal bronchial proliferation
that may involve either lung or any lobe. In greater than
95% of cases, CCAM is limited to one lobe or segment,
with 2% to 3% of CCAMs occurring bilaterally and with
the right and left lungs equally affected.
41
Cystic adenomatoid malformation results from a pul-
monary insult during embryologic development of the
Right Left
FIGURE 36-2. Pulmonary hypoplasia. Axial sonogram
demonstrates mediastinal shift to the right. No lung mass
is present. Presumptive diagnosis was pulmonary hypoplasia,
confirmed postnatally. (Courtesy Richard Barth, MD, Stanford
University.)
TABLE 36-3. DIFFERENTIAL DIAGNOSIS OF ECHOGENIC LESION IN FETAL THORAX
ABNORMALITY LOCATION DISTINGUISHING FEATURES
Congenital cystic adenomatoid
malformation (CCAM)
Sequestration Unilateral; left lower lobe most often Systemic blood supply
Congenital lobar emphysema Unilateral; upper lobe most often Similar to microcystic CCAM; enlarged echogenic lung
Congenital diaphragmatic hernia
(CDH)
Congenital high airway obstruction
(CHAOS)
Unilateral
(2%-3% bilateral)
Typically unilateral; left sided most often Peristalsis of bowel in chest
Bilateral Distended trachea and main central airways
Cystic and solid
with mediastinal shift
Stomach above diaphragm
Absence of part of the diaphragm
Symmetrical bilateral enlarged lungs with eversion of
hemidiaphragms
1278 PART IV ■ Obstetric Sonography
TABLE 36-4. DIFFERENTIAL DIAGNOSIS OF CYSTIC LESION IN FETAL THORAX
ABNORMALITY BILATERAL VS. UNILATERAL DISTINGUISHING FEATURES
Congenital cystic adenomatoid
malformation (CCAM)
Congenital diaphragmatic hernia
(CDH)
Teratoma Mass does not obey lobar boundaries; may have calcifications.
Neurenteric cyst Adjacent to spine
Bronchogenic cyst Typically single cyst
Esophageal duplication Adjacent to esophagus
Lymphangioma Crosses anatomic boundaries
bronchial tree before the seventh week of gestation,
resulting in failure of bronchial maturation and lack of
normal alveoli. Histologically, CCAM is differentiated
from other lung masses by the absence of bronchial
cartilage and bronchial tubular glands, with overproduction of terminal bronchiolar structures without alveolar
differentiation, except in the subpleural areas.
resulting cystic lesions result in enlargement of the
affected lobe (or segment). If sufficiently large, CCAM
will result in mediastinal shift and interfere with normal
alveolar development in the adjacent lung. Communication with the tracheobronchial tree usually is retained,
with vascular supply and venous drainage to the pulmonary circulation, unless CCAM is associated with
sequestration.
Typically, CCAMs are divided into three types. Type
I is the most common, with variably sized cysts measuring 2 to 10 cm. Type II has uniform cysts less than 2 cm
in greatest diameter. Type III CCAM has small cysts less
than 0.5 cm and appears grossly solid.
Sonographic diagnosis is made as early as 16 weeks.
CCAM may appear as a solid echogenic lung mass or as
a mixed, cystic and solid mass (Fig. 36-3; Video 36-1).
Color Doppler ultrasound may demonstrate vascular
flow to the lesion from a branch of the pulmonary artery.
Typically, there is no systemic feeding vessel, although
as mentioned, CCAM can occur in concert with sequestration. The lesions with microcysts appear solid and
echogenic, whereas the macrocystic CCAM has easily
demonstrable cysts. Occasionally, only a single large cyst
is visualized.
As with any chest mass, it is important to assess
for associated mediastinal shift, polyhydramnios, and
hydrops because these factors impact prognosis and management.
46,47
It is the size of the CCAM rather than the
size of the cysts that determines whether or not the fetus
develops hydrops. Large CCAMs result in cardiac compression, leading to altered hemodynamics and hydrops
as a result of elevated central venous pressure.
hydrops as a result of CCAM has an anticipated mortality
of 100%. Hydrops is therefore an indication for in utero
fetal therapy, which generally consists of either draining
Unilateral
(2%-3% bilateral)
Typically unilateral Peristalsis of bowel in chest
Associated with echogenic lung mass, typically multiple cysts
Stomach above diaphragm
the largest cyst with a single stick procedure (Fig. 36-3,
G ) or placing a shunt. Rarely is open fetal surgery indi-
cated. A 2006 meta-analysis showed that shunting of
CCAMs improved survival in fetuses with hydrops,
42-44
The
versus no effect on survival in fetuses with chest masses
without hydrops.
in cases of CCAM ranges between 29% and 62%, but
49
The success with open fetal surgery
has the limitation of expected preterm delivery.
natal aspiration of a macrocystic CCAM is an effective
treatment at times
51
but frequently is ineffective because
of rapid reaccumulation of the cysts. Steroid therapy may
also be beneficial, given the hypothesis that increasing
lung maturity improves survival.
Associated anomalies, most often renal, intestinal,
and cardiac, are present in up to 26% of cases,
frequently when CCAM is bilateral.
anomalies in association with CCAM are rare. Thus, if
no other structural abnormalities are detected, karyotyp-
45
ing usually is not performed.
Magnetic resonance imaging can be helpful in evaluation and management of CCAM (Fig. 36-3, H, I ),
particularly for fetal surgeons when hydrops and polyhydramnios necessitate surgery.
lesions have very high signal intensity on T2-weighted
imaging, almost equal to that of amniotic fluid, and
much higher than that of the surrounding unaffected
lung tissue. Type III CCAM lesions have moderately
high signal intensity and are relatively homogeneous. As
the lesions regress, they develop low signal intensity on
T2-weighted imaging
54
and may be associated with a
small pleural effusion.
If the fetus does not develop hydrops before 26 weeks,
the prognosis is generally good.
lance of the growth of these lesions is typically performed
at frequent intervals (every 1-2 weeks) throughout the
second trimester. CCAMs tend to regress in the third
trimester. As they regress, they may become isoechoic
48
Untreated
with normal adjacent lung and thus may become inapparent late in gestation. If originally present, mediastinal
shift can resolve. Although regression of CCAM on prenatal ultrasound is common, the lesion does not completely disappear.
55
Up to 40% of neonates with prenatal
52
36,45
41
Chromosomal
53
Type I or type II CCAM
55,56
Therefore, surveil-
50
Ante-
more
Left
Chapter 36 ■ The Fetal Chest 1279
Right
C
HT
F
I
Left
B
Left
E
H
A
D
Right
Right
G
FIGURE 36-3. Congenital cystic adenomatoid malformation (CCAM). A, Axial sonogram at 28 weeks shows a homo-
geneously echogenic mass (calipers) in the mid–left hemithorax with no large cysts or feeding vessels. There is mild mediastinal shift to
the right. B, Axial sonogram of right-sided CCAM (arrow) at 20 weeks with small cysts, the largest of which is 8 mm (arrowhead). There
is moderate mediastinal shift to the left. C, Sagittal oblique sonogram shows CCAM everting the hemidiaphragm (arrow). D, Transverse
view of chest with CCAM containing small cysts and mild mediastinal shift. E and F, Axial and oblique coronal images at 25 weeks in a
macrocystic CCAM (arrow) with eversion of the hemidiaphragm, trace ascites (arrowhead), and severe mediastinal shift with compression
of the heart (HT). G, Ultrasound-guided percutaneous drainage of CCAM. A 20-gauge needle was inserted into the largest cyst with relief
of cardiac compression. H, Coronal T2-weighted MR image shows a well-circumscribed area of T2 hyperintensity (arrow) in the left
upper lobe. I, Oblique coronal T2-weighted MR image shows a well-circumscribed area of low T2 signal, in a fetus with a typical, resolving CCAM.
diagnosis of CCAM are symptomatic at birth and require
intervention or respiratory support.
57
Therefore, delivery
should be at a site with appropriate neonatal intensive
The timing of surgical resection of CCAM remains controversial, but most centers favor elective surgical resection early in life.
60
care unit (NICU) services. Because the lesion may be
inapparent on chest radiography after birth, postnatal
computed tomography (CT) or MRI may be needed to
visualize the lesion. Postnatal removal of asymptomatic
masses is performed because of potential secondary
infection, hemorrhage, and risk of carcinomas arising in
CCAM.
normal lung growth if the lung lesion is not resected.
58
In addition, CCAM may prevent future
59
Bronchopulmonary Sequestration
Bronchopulmonary sequestration is an anomaly in which
nonfunctioning pulmonary tissue is not in normal continuity with the native tracheobronchial tree
a blood supply from the systemic circulation. Sequestrations account for up to 6% of congenital lung
61
and has
1280 PART IV ■ Obstetric Sonography
62,63
malformations.
Concomitant anomalies associated
with sequestration include CDH, diaphragmatic eventration and paralysis, bronchogenic cyst, ectopic pancreas, vertebral anomalies, and foregut duplication.
There are two main types of sequestration: intralobar
and extralobar. A third variant is suggested when communicating bronchopulmonary foregut malformation is
present.
64
Extralobar sequestration represents the vast majority
of fetal sequestrations. This lesion is a supernumerary
lung bud invested by its own pleura, typically deriving
its blood supply from the splanchnic vessels surrounding
the foregut, which results in the systemic blood supply.
65
The venous drainage is usually through a single vessel
into the azygous, hemiazygos, and/or the vena cava
system. In up to 25% of cases, however, the extralobar
sequestration is partially drained through pulmonary
veins. Extralobar sequestration is typically found in the
left posterior costodiaphragmatic sulcus between the
lower lobe and the hemidiaphragm.
66
Extralobar sequestrations occur below the diaphragm in suprarenal locations in 10% to 15% of cases (with a differential diagnosis
of neuroblastoma and adrenal hemorrhage).
sequestration may present as a mediastinal or pericardial
68
mass.
Intralobar sequestration comprises abnormal lung
tissue with systemic arterial supply within the normal
lung, sharing the visceral pleura and draining to pulmonary veins.
66
It occurs more often in the lower lobe than
upper lobe and slightly more often on the left.
Sequestration can be detected on prenatal sonogram
as early as 16 weeks’ gestation.
69
Typically, a sequestration appears as a well-defined, homogeneous, echogenic
wedge-shaped pulmonary mass in the lower lobe adjacent to the hemidiaphragm (Fig. 36-4). Classically, these
lesions do not have cysts. However, cysts can result from
67
Rarely,
63
1
A
C
B
FIGURE 36-4. Bronchopulmonary sequestration at
19 weeks’ gestational age. A and B, Axial and oblique
coronal images show a left-sided, homogeneous echogenic mass
with mild mediastinal shift and flattening of the hemidiaphragm.
C, Color Doppler demonstrates a feeding vessel extending directly
from the infradiaphragmatic aorta to the mass, thus proving it is a
sequestration.
dilated bronchioles or hybrid lesions of concomitant
CCAM. Sequestration can be distinguished from other
congenital lung masses by identifying on Doppler interrogation a systemic artery arising from the thoracic or
abdominal aorta feeding the mass. Determination of
where the vessel arises is important for counseling parents
about the approach that will be needed for postnatal
surgical removal of the mass.
Small sequestrations with minimal mediastinal shift
have a benign clinical course.
38
As with other chest
masses, a large sequestration may result in mediastinal
shift. However, most prenatally detected sequestrations
are of small or medium size. These lesions usually regress
in size during gestation.
38,47
Large sequestrations can be
complicated by pleural effusions and with hydrops can
lead to increased prenatal mortality. For such complicated cases, the pleural effusion can be treated with pleuroamniotic shunting and drainage.
70,71
Chapter 36 ■ The Fetal Chest 1281
Right
Congenital Lobar Emphysema
Congenital lobar emphysema (CLE) is a rare congenital
lung malformation manifesting as progressive lobar overinflation of the lung without destruction of alveolar
septa. CLE results from maldevelopment of a lobar or
segmental bronchus. It occurs in the upper lobes more
than lower lobes. On prenatal ultrasound, CLE is similar
in appearance to microcystic CCAM, manifesting as an
echogenic mass that is relatively large and typically causes
mediastinal shift because of its size
CCAM, the lesion can regress in utero.
72
(Fig. 36-5). As with
73
Because of the
nonspecific appearance, even if it regresses in size, postnatal follow-up is required because air trapping and
respiratory distress may necessitate lobar resection early
in neonatal life.
74
CONGENITAL HIGH AIRWAY
OBSTRUCTION
Congenital high airway obstruction (CHAOS) is a spectrum of conditions characterized by incomplete or
complete obstruction of the high fetal airway.
fetal abnormality that obstructs the larynx or trachea,
causing intrinsic atresia or extrinsic compression results
in CHAOS. Laryngeal atresia is the most frequent
cause. Other etiologies include laryngeal or tracheal
webs, laryngeal cysts, tracheal atresia, subglottic stenosis or atresia, and laryngeal or tracheal agenesis.
If untreated, CHAOS is almost always lethal.
Although sporadic with unknown incidence, CHAOS
can be part of various chromosomal disorders.
also be familial with autosomal dominant inheritance
and variable expression.
80
Laryngeal atresia can occur as
part of Fraser syndrome (tracheal or laryngeal atresia,
renal agenesis, microphthalmia, and syndactyly or polydactyly) with autosomal recessive inheritance.
76
78,79
79,81
75,76
It can
Any
77
Left
FIGURE 36-5. Congenital lobar emphysema. Axial
image of the chest shows an enlarged, diffusely echogenic right
lung. Although this appearance would more often be caused by a
congenital cystic adenomatoid malformation, the postnatal diagnosis was congenital lobar emphysema. (Courtesy Richard Barth,
MD, Stanford University.)
Prenatal ultrasound findings can be visualized as early
as 16 weeks’ gestation.
82
Findings include bilateral symmetrically enlarged echogenic lungs, dilated fluid-filled
trachea and central bronchi, and flattened or everted
diaphragms
83,84
(Fig. 36-6). The heart usually assumes a
more central and anterior position than normal and is
often compressed as the size of the lungs increases.
Frequently, there are associated findings of ascites and
other signs of hydrops. The mechanism of ascites may
be from compression of the heart and great vessels by
the enlarged lungs.
85
Either polyhydramnios or oligohy-
dramnios may be present.
The lungs are distended and appear homogeneously
echogenic because of increased fluid and increased lung
growth induced by the upper airway obstruction.77 The
increased number of tissue-fluid interfaces produces the
hyperechoic appearance of the lungs. Lung volume can
increase up to 15 times the expected size. The hyperplastic lungs are edematous but otherwise histologically
normal.
77
Magnetic resonance imaging can be used to identify
the region of obstruction and assist in decisions regarding in utero intervention and intrapartum procedures.
Characteristic findings include increased lung volume,
diffuse increase in lung intensity on T2-weighted images,
and a dilated fluid-filled trachea.
83
Greater than 50% of fetuses with laryngeal obstruction have associated abnormalities, most often in the
77
1282 PART IV ■ Obstetric Sonography
Left
A B
Right
Right
Left
C D
FIGURE 36-6. Congenital high airway obstruction syndrome (CHAOS) at 19 weeks. A and B, Axial and coronal
views of the chest show diffusely enlarged, echogenic lungs bilaterally with eversion of the hemidiaphragms (arrows) and ascites (arrowhead).
C and D, Axial and coronal T2-weighted MR images show increased lung volume and fluid-filled airways (arrows). (Courtesy Katherine
Fong, MD, University of Toronto.)
renal system and central nervous system (CNS). At
times, CHAOS can be present in association with a
tracheoesophageal fistula. This fistula acts as an alternative pathway for the accumulated fluid, leading to a
decrease in lung volume, reversal of diaphragmatic eversion, and resolution of ascites and polyhydramnios.
75
If untreated, laryngeal and tracheal atresia can lead to
utero intrapartum treatment (EXIT) procedure.
The EXIT procedure involves tracheostomy placement
below the level of the obstruction while maternal placental circulation is maintained.
BRONCHOGENIC CYST
86,87
death either in utero from hydrops or within minutes
after birth from respiratory compromise. Neonatal survival is possible if the delivery is performed with the ex
Bronchogenic cysts are rare anomalies that result from
abnormal budding or branching of the tracheobronchial
Chapter 36 ■ The Fetal Chest 1283
FIGURE 36-7. Bronchogenic cyst at 22 weeks. Color
Doppler transverse image shows a cyst (arrow) adjacent to vessels
without associated solid mass.
tree. They are most often located in the mediastinum in
the subcarinal region.
88
However, 15% of bronchogenic
cysts occur in the lungs, pleura, and diaphragm. They
account for 11% to 18% of mediastinal masses in infants
and children.
89,90
The cyst is lined by ciliated mucussecreting bronchial epithelium and may be mucus filled.
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. 36-7), at times with layering echogenic material.
91,92
If the cyst does not cause mass effect, it typically will
not cause a problem in utero. However, if the cyst
compresses the airway, it can lead to airway obstruction
at birth.
93
The main differential diagnosis is CCAM.
However, CCAM usually has more than one cyst and an
associated echogenic mass with mass effect. If a bronchogenic cyst causes obstruction, it may lead to the distal
lung accumulating fluid, masquerading as an echogenic
lung lesion such as CCAM or sequestration. Fetal MRI
can be helpful in cases with unclear diagnosis.
93
Surgical
resection for bronchogenic cysts is performed postnatally
because of the associated increased risk for hemorrhage,
infection, or malignancy.
94
NEURENTERIC CYST
Neurenteric cysts represent a posterior enteric remnant
caused by incomplete separation of the notochord from
the foregut during embryogenesis. They typically occur
in the posterior mediastinum or in the spinal canal. The
cysts can have a septated or bilobed appearance. Associated spinal abnormalities are typically present.
PLEURAL EFFUSION
Fetal pleural effusion is rare, with an incidence of up to
1 in 15,000 pregnancies.
affected than females.
abnormal. If sufficiently large, pleural effusion may
result in mass effect, leading to compression of the heart
and hydrops as well as compression of the lungs, resulting in pulmonary hypoplasia.
Primary pleural effusion is most often caused by
chylothorax,
103
which results from defective development of the lymphatic system. Any insult to the course
of the thoracic duct in the posterior mediastinum in the
fetal chest can result in chylous fetal pleural effusion.
This can be on either the right or the left side, because
the thoracic duct in the posterior mediastinum crosses
from right to left at the fifth thoracic level. Primary
pleural effusion is suspected when the effusion is unilateral or is much larger on one side than the other, and no
other signs of hydrops are present. However, once
hydrops develops (cardiac compression from unilateral
effusion), this distinction can be difficult.
Primary chylothorax is associated with aneuploidy in
1.8% to 5.8% of cases.
in neonates is identified when fluid contains more than
1.1 mmol/L triglycerides with oral fat intake, with lymphocyte proportion exceeding 80%.
fetus is fasting in utero, and the mean percentage of
lymphocytes in the blood of normal fetuses is normally
greater than 80%.
108
apply in utero.
Secondary pleural effusion occurs in association
with aneuploidy, infection, genetic syndromes, and
other structural malformations.
typically present with bilateral pleural effusions (particularly in fetuses with hydrops),
unilateral effusion.
Pleural effusions appear on prenatal ultrasound as
anechoic fluid collections in the pleural space, leading to
the appearance of the lung floating in the fluid, surrounded by the chest wall and diaphragm
Video 36-2). Small effusions appear as an anechoic thin
rim outlining the lungs and the mediastinum. Larger
unilateral effusions result in mass effect causing mediastinal shift and flattening or eversion of the diaphragm.
If isolated and small, pleural effusions have a benign
course. If large with mass effect, untreated fetal pleural
effusion has a mortality rate of 22% to 53%.
Small pleural effusions do not shift the mediastinum.
Pleural effusions associated with hydrops may be unilateral or bilateral, often beginning as unilateral collections
that progress bilaterally. If mediastinal shift is visualized
in association with a small pleural effusion, a chest mass
99,100
101
Males are slightly more
Any fluid in the pleural space is
102
105,106
By definition, chylothorax
107
However, the
Therefore, these parameters do not
105,109
These syndromes
104
but occasionally with
110
95-98
104
(Fig. 36-8;
99,101,104,111,112
1284 PART IV ■ Obstetric Sonography
Left
A
Right
B
C D
Left
Right
R
L
E F
FIGURE 36-8. Pleural effusion. A and B, Axial and coronal views of small pleural effusions at 25 weeks (arrows). C, Axial view
of effusion at 28 weeks with mild mediastinal shift. D, Axial view shows moderate bilateral effusions outlining the lungs. The effusions
are about the same size, so there is no mediastinal shift. E and F, Axial and oblique sagittal views at 17 weeks show a large left effusion
(L) with severe mediastinal shift to the right (R).
such as a hernia or congenital pulmonary malformation
should be sought. Larger effusions will lead to flattening
of the hemidiaphragms, and when sufficiently large,
mediastinal shift.
Prenatal pleural effusion has a variable natural course
ranging from spontaneous resolution to progressive
development of hydrops fetalis and polyhydramnios
with high risk for perinatal morbidity and mortality.
104
Good prognostic factors include absence of associated
abnormalities, unilateral effusion, no associated hydrops,
and spontaneous resolution, which may occur in up to
20% (has been associated with 100% survival).
101,104,112
Poor perinatal outcome is associated with pleural effusion in association with hydrops, underlying structural
abnormalities, pulmonary hypoplasia, and early gestational age at diagnosis.
101,102
Pleural effusions are treated by drainage if the effusion
is isolated (or asymmetrical) without additional anomalies, typically in fetuses at risk for developing hydrops
(i.e., those with severe mediastinal shift or with other
signs of hydrops already present).
effusion is drained with a single stick procedure.
recurs, placement of a thoracoamniotic shunt is an
114
option.
A recent systematic review of prenatal inter-
49
Typically, a pleural
113
If it
vention for isolated primary pleural effusion without
hydrops suggested that survival rates after prenatal intervention are as high as 60%.
100
Case reports of other
treatment options include pleurodesis and intrapleural
injection of autologous blood, which have a survival rate
of 80%.
115,116
A series of 44 fetuses found thoracoamniotic shunts to have a high survival rate in nonhydropic
fetuses of 100%, with survival of 50% in the hydropic
4
Risks of prenatal thoracoamniotic shunts include
group.
fetal hemorrhage, blockage or migration of the shunt,
and placental abruption or preterm labor. In cases of
large effusions, drainage immediately before delivery can
assist in airway management at birth.
PERICARDIAL EFFUSION
In contrast to pleural effusions that surround the lungs
and compress the tissue medially, pericardial effusions
are anteromedial fluid collections. Fluid collections of up
to 2 mm in thickness are common, and a small amount
of pericardial fluid (up to 7 mm, in isolation) can be a
normal finding.
117
A large pericardial effusion compresses
the lungs against the posterior chest wall (Fig. 36-9). The
heart is visualized as “floating” within the anterior thoracic fluid collection.
CONGENITAL DIAPHRAGMATIC
HERNIA
Congenital diaphragmatic hernia results from failure
of the pleuroperitoneal canal to close at the end of
Chapter 36 ■ The Fetal Chest 1285
FIGURE 36-9. Pericardial effusion. Note how the lungs
(arrows) are compressed posteriorly by the effusion surrounding
the heart.
organogenesis.
118
A “dual hit” hypothesis suggests that
the defect arises in the embryologic period (first hit) and
during further gestation, lung development is impaired
(second hit).
119
The defect in the diaphragm allows herniation of viscera into the chest. Mass effect from visceral
organs in the chest has an adverse impact on the normal
development of the fetal cardiac and pulmonary systems.
Thus, CDH is associated with substantial morbidity
and mortality.
120-123
The incidence of CDH is about 1
in 3000 births.
The majority of hernias are on the left (84%) and
occur predominantly through the posterolateral foramen
of Bochdalek. CDHs occur on the right in 10% to 15%
of cases and are bilateral in less than 5%.
few cases of Morgagni hernia (anterior diaphragmatic
defect) have been reported prenatally.
124,125
126-128
agenesis of the diaphragm, herniation of the central
tendinous part, pericardial hernia, and eventration of
the diaphragm are rare manifestations.
9
Left-Sided Hernia
Left-sided CDH is most often diagnosed when the
stomach is in the chest near the left atrium, with absence
of the normal stomach below the diaphragm (Fig. 36-10;
Videos 36-3 and 36-4). Small and large bowel as well
as the liver, spleen, and kidney can herniate into the
thorax. As the abdominal contents herniate into the
chest, mediastinal shift occurs with the heart deviating
to the right.
9,125,129
In large hernias, mediastinal shift is
severe, leading to vascular compromise. Compression of
the heart, impaired swallowing, and partial obstruction
of the gastrointestinal tract lead to polyhydramnios,
which is present in up to 69% of cases, particularly late
in gestation (by the third trimester).
121,130,131
Only a
Complete
1286 PART IV ■ Obstetric Sonography
Li
Left
A
D
Right
B
E
C
C
1
F
G
FIGURE 36-10. Left-sided congenital diaphragmatic hernia (CDH). A, Axial view of chest at 28 weeks’ gestation shows
the stomach (arrow) in the chest with mediastinal shift to the right. B, Coronal image in a different fetus at 28 weeks shows a slightly
distended stomach (arrow) in the chest. C, Oblique sagittal image shows a large amount of liver (Li) in the chest. Note the hepatic vessels
(arrows). D, Axial view of abdomen shows abnormal course of umbilical vein (arrowhead) resulting from the liver herniation into the
chest. E, Oblique axial view of chest shows kinked hepatic vessels. F, Axial view in the right lower quadrant shows the associated polyhy-
dramnios complicating the pregnancy in the same fetus. G, Sagittal T2-weighted fetal MR image shows the small bowel (arrow) and colon
(arrowhead) in chest with small pleural effusion. H, Sagittal T1-weighted fetal MR image shows liver (arrow) in chest. Note bright signal
of meconium in colon (C) in chest, as well as small bowel loops (arrowhead) in chest. I, Postnatal radiograph shows the bowel in the left
chest, nasogastric tube in the left chest, and a tiny, hypoplastic right lung.
Because left-sided hernias with mediastinal shift compress the left heart, they can lead to underdevelopment
of the left heart. Mediastinal shift often makes it difficult
to assess for hypoplastic left-sided heart in association
with CDH, versus compression caused by mediastinal
H
shift. Because of the high rate of associated cardiac
abnormalities, formal fetal echocardiography is indicated
in fetuses with CDH.
Prenatal sonographic diagnosis of CDH can be made
as early as the first trimester.
I
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With the increased use
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