Unilateral hyperlucent hemithorax is a common radiographic finding in pediatric patients, caused by various congenital and acquired pulmonary conditions. Diagnostic evaluation is essential to determine if the hyperlucency is due to true lung pathology or opposing lung opacity, with further imaging investigations often required. Conditions include post-infectious pneumatoceles, congenital lobar emphysema, and airway obstructions, which may lead to significant respiratory complications if not properly managed.

1. PRESENTED – DR. ANNIE AGARWAL

2.  Unilateral hyperlucent hemithorax is a common pediatric
chest radiographic finding .
 It may result from congenital or acquired conditions
involving the pulmonary parenchyma, airway, pulmonary
vasculature, pleural space, and chest wall, as well as from
technical factors such as patient rotation.
 When evaluating a patient with this finding, it is important
to establish whether the apparent unilateral hyperlucent
hemithorax is truly too lucent (hypoattenuating) or if the
contralateral hemithorax is too opaque (hyperattenuating).
 Lung defect depends upon the pulm vsl abnormality n not
on the size of the lung.

5.  When detected at frontal radiography, further
evaluation with additional radiography,
computed tomography (CT), or bronchoscopy
may be required.

7.  Rare in children, with both lungs affected in
most cases.
 CAUSES:
◦ idiopathic bullous emphysema,
◦ late sequelae of chronic lung disease associated
with premature birth (bronchopulmonary dysplasia),
◦ pulmonary interstitial emphysema (as well as
persistent pulmonary interstitial emphysema) in
neonates.

8.  Emphysematous changes in bronchopulmonary dysplasia may appear
asymmetric, an appearance that sometimes is due to the presence of
large bullae
 Unilateral hyperlucent hemithorax in an 18-year-old man with a
history of chronic lung disease associated with premature birth (at 26
weeks gestation) and severe right lung emphysema.

9.  Pulmonary interstitial emphysema, a form of barotrauma that
results from positive pressure ventilation, appears as numerous
cystic lucencies within the interstitium at both radiography and
CT.
 It may be segmental, lobar, unilateral, or bilateral
 Left lung barotrauma due to positive pressure ventilation in a
13-day-old neonate.

10.  discrete, thin-walled, gas-containing collections within the lung
parenchyma.
 They may be Post-infectious or post-traumatic, or result from
positive pressure ventilation– related barotrauma and ingestion of
caustic material (eg, hydrocarbons).
 Postinfectious pneumatoceles are most common among infants and
young children, (70% in children under the age of 3 years) and most
frequently complicate staphylococcal pneumonia.
 Less common causative organisms include Pneumococcus, Klebsiella
pneumoniae, E. coli, and H. influenzae.
 Pneumatoceles typically appear within 1 week of onset of infection,
and most spontaneously disappear within weeks to months after the
infection has resolved.
 Rarely, persistent pneumatoceles may require percutaneous catheter
drainage or surgical management.

11.  Post-traumatic pneumatoceles result from blunt trauma, with
gas becoming entrapped within areas of pulmonary
parenchymal laceration. These are observed within hours of
the trauma, noted at initial posttraumatic chest radiography,
and spontaneously resolve within 3 weeks. These may be
solitary or multiple and generally spare the lung apices.
 At chest radiography and CT, pneumatoceles appear as well-
defined pulmonary parenchymal cystic structures, usually
with a thin wall. They may be entirely filled with gas, or an
air-fluid level may be seen.
 C/L mediastinal shift - large pneumatocele.
 Compressive atelectasis - result of mass effect, may affect
adjacent pulmonary parenchyma or the contralateral lung.
 Rupture of large pneumatoceles complicated by tension
pneumothorax.
 A coexisting pulmonary contusion is commonly observed in
the setting of posttraumatic pneumatoceles.

12. Pneumatocele in a 3-month-old girl with a history of
chronic lung disease associated with premature birth
and methicillin-resistant Staphylococcus aureus
(MRSA) pneumonia. She was born at 26 wk gestation.

14.  most common between 6 months and 3 years of age, but it may
occur earlier or later in childhood.
 Most are diagnosed within hrs to a few days after the event, rarely,
weeks to months later.
 Most aspirated foreign bodies are located within the right main-
stem bronchus :
◦ larger diameter
◦ more vertical orientation compared with the left bronchus
◦ the carina is usually shifted to the left of the midline.
 less commonly located within the trachea or larynx.
 may be life threatening, and children may present with cough,
respiratory difficulty, wheezing, hemoptysis, or recurrent
pneumonia.
 Most aspirated foreign bodies are organic (eg, food) and are not
radiopaque at chest radiography

15.  secondary radiographic signs:
◦ ipsilateral pulmonary hyperinflation due to air trapping,
◦ ipsilateral pulmonary hyperlucency
◦ pulmonary vasoconstriction, and
◦ ipsilateral postobstructive atelectasis or pneumonia.
 There are specific techniques that may help accentuate air
trapping related to foreign body aspiration.
◦ In older, cooperative children, inspiratory and expiratory phase
images may demonstrate failure of the affected lung to collapse at
expiration.
◦ In younger, less cooperative children, lateral decubitus images
may depict failure of the affected lung to collapse when in a
dependent position
 20%–35% children have normal chest radiograph.
 Chronic aspiration complicated by bronchiectasis and
abscess formation.
 Although chest CT with virtual bronchoscopy has been
described as a useful tool for depicting aspirated foreign
bodies, it is not commonly employed.

16.  Aspirated foreign
body in a 19-month-
old boy with a
persistent cough.
PA chest radiograph Right lateral decubitus
Left lateral decubitus

17.  Thought to be secondary to infectious obliterative bronchiolitis and
distal airspace destruction in infancy or childhood
 Adenovirus, respiratory syncytial virus, and Mycoplasma organisms.
 may be either unilateral (affecting one or more lobes) or bilateral .
 C/F -chronic cough, wheezing, or recurrent pneumonia, although
some individuals may be asymptomatic.
 At pulmonary function testing, an obstructive lung disease pattern
seen.
 In appropriate clinical setting, radiography and CT usually are
sufficient to diagnose the condition.
 detected as early as 9 months after the initial infectious insult.

18.  Affected lung parenchyma appears hyperlucent, a result of
air trapping due to bronchiolar obstruction, and blood
vessels within the affected lung are decreased in number
and caliber.
 Affected lung commonly appears small, although
hyperexpansion due to collateral ventilation and air
trapping may be seen.
 Incomplete filling of ipsilateral peripheral bronchioles with
contrast material at bronchography.
 Ipsilateral bronchiectasis also is a common finding.
 The use of high-resolution CT during expiration may help
determine the extent of disease (which is seen as air
trapping) which the chest radiography fails to depict.
 Affected pulmonary parenchyma also may demonstrate a
mosaic attenuation pattern, a result of areas of preserved
normal lung.

19.  Presumed Swyer-James syndrome in a 16-year-
old girl with a history of severe viral respiratory
infection as a child and fixed obstructive airway
disease at pulmonary function testing.

20.  or congenital pulmonary overinflation,
 most commonly affects a single lobe of the lung, although multiple
lobes or specific lobar segments may be involved.
 The left upper lobe is most commonly affected, although the right
middle and upper lobes are also commonly involved.
 Causes:
◦ deficient bronchial cartilage (bronchomalacia),
◦ endobronchial lesions (eg, mucosal web),
◦ extrinsic bronchial compression (eg, an anomalous vascular structure or
mass)—all of which result in airway luminal narrowing and obstruction.
 The obstructed lung becomes hyperinflated by collateral air drift.
 15% have ass. congenital heart disease such as PDA & VSD.
 C/F- respiratory distress during early childhood, with 50%
presenting during the first 2 days of life.

21.  On chest radiographs obtained immediately
after birth: appears as a hazy masslike
opacity, a result of trapped fetal lung fluid.
 Congenital lobar emphysema of the right
upper lobe in a 1-day-old boy. Chest
radiograph at 1 day. Sagittal reformation CT
acquired 6 mths later.

22.  A few hours to several days after birth, this fluid is replaced with air, and
affected lung appears hyperlucent and hyperexpanded at both X ray and
CT.
 Atelectatic collapse of adjacent pulmonary parenchyma andC/L
mediastinal shift may be present, a result of mass effect of the
hyperinflated lung.
 Vascular structures within the affected lung appear attenuated and
displaced.
 Left-upper-lobe congenital lobar emphysema in a 2-day-old boy

23.  Pediatric endobronchial tumors are rare
 Tumors that may arise from the tracheobronchial tree- carcinoid
tumor (most common), mucoepidermoid carcinoma, and
inflammatory (myofibroblastic) pseudotumor.
 At radiography, a circumscribed central parahilar mass may or
may not be present in the setting of carcinoid tumor.
 80% endobronchial carcinoid tumors are central in location.
Endobronchial tumors rarely are peripheral (manifesting as SPN).
 Secondary signs: ipsilateral air trapping, mucus plugging (seen
as branching V- and Y-shaped areas of opacification), and
postobstructive atelectasis or pneumonia.
 At CT, bronchial and endobronchial carcinoid tumors usually are
parahilar and well defined with homogeneous
hyperenhancement, and eccentric calcifications may be present.
 Masses arising from the airway may have a substantial
extrabronchial component.

24.  Carcinoid tumor in a
16-year-old boy.
Axial CECT image
shows a
hyperenhancing
mass (arrows)
arising from the
central right
bronchial tree (*). A
branching Y-shaped
area of the right
lung with peripheral
areas of low
attenuation
(arrowheads) is also
seen, a result of
mucus impaction
within the airway.

25.  Mucoepidermoid carcinoma arising from
the left main-stem bronchus in a 15-year-
old girl. (a) Axial CECT image shows a
hyperenhancing mass (arrow) within the left
main-stem bronchus. (b) Volume-rendered
CT image shows air trapping within the left
lung and an endobronchial filling defect
(arrow). (c) Reconstructed endobronchial CT
image shows the mass (*) within the left
main-stem bronchus.

26.  result from both congenital and
acquired extrinsic bronchial
compression of various causes, and a
variety of mediastinal masses may
exert substantial mass effect on the
airway with resultant air trapping.
 Pericardial lipoblastoma :
 PA chest radiograph (a) and axial CT
image (b) show a hyperexpanded,
hyperlucent, hypovascular left lung.
 Axial CT image shows the mass (*)
extrinsically compressing the left
main-stem bronchus (arrow).

27.  Several vascular structures also may cause substantial bronchial
narrowing and manifest with either air trapping or atelectasis, such as
major aortopulmonary collateral arteries, dilated or anomalous
pulmonary arteries (including pulmonary slings), and repaired
interrupted aortic arch .
 Tetralogy of Fallot, pulmonary atresia, and major aortopulmonary
collateral arteries in a 1-month-old boy. (a) AP chest radiograph shows a
hyperlucent, hyperexpanded, hypovascular right lower lobe. (b) Coronal
reformatted contrast-enhanced CT image shows multiple large
aortopulmonary collateral arteries, which surround and compress the
right main-stem bronchus (arrow).

28.  Accidental bronchial
endotracheal-tube intubation is
a common cause of unilateral
hyperlucent hemithorax.
 Hyperaeration of the i/l lung,
and the c/l lung may appear
collapsed, a result of generalized
hypoaeration and occlusion of its
main-stem bronchial orifice.
 Complications: ipsilateral
barotrauma from positive
pressure ventilation (eg,
pneumothorax) and hypoxia.

29.  focal congenital obstruction of the
airway,
 typically occurs at the segmental level
and most commonly affects the
apicoposterior segment of the left upper
lobe,
 C/F - asymptomatic, and the condition
is incidentally discovered at imaging.
 At radiography and CT, hyperinflation
and hyperlucency of the affected lung
due to air trapping, with a relative
paucity of pulmonary blood vessels.
 a branching, nonenhancing parahilar
masslike (or tubular) abnormality is
commonly observed, a result of mucus
impacted within more peripheral dilated
airways.

31.  complete, unilateral absence of lung parenchyma and
associated blood vessels and airways.
 results from an insult during the 4th wk of gestation.
 Failure of the lung to develop- left > right
 patients with an absent right lung have a worse prognosis.
 associated with pulmonary sling (passage of the left
pulmonary artery between the trachea and esophagus) and
complete tracheal rings.
 C/F – asymptomatic in childhood and the condition may
manifest in adulthood.

32.  opaque hemithorax.
 At both radiography
and CT, resultant I/L
mediastinal shift and
marked C/L
pulmonary
hyperexpansion and
hyperlucency are
seen.

33.  CT : I/L lung parenchyma,
blood vessels, and airways are
absent.
 Volume-rendered images of
the airway may depict
narrowing due to tracheal
kinking from mediastinal shift,
extrinsic impression from a
pulmonary sling, and complete
tracheal rings.
 CECT image shows
hyperinflation of the right lung
and absence of the left lung
and left pulmonary artery.
White * = main pulmonary
artery, black * = right
pulmonary artery.

34.  Right pulmonary agenesis in a 3-day-old girl.
 (a) Axial CECT image shows absence of the right lung. The left lung is
hyperinflated, and the left pulmonary artery (*) courses between the
trachea and esophagus, findings indicative of pulmonary sling. The
trachea is narrowed by the anomalous left pulmonary artery.
 (b) Volume-rendered CT image (posterior view) of the airway and left
lung shows kinking of the trachea (arrow), a result of mediastinal shift.
Complete tracheal rings (arrowheads) also are seen.

35.  associated with decreased numbers and sizes of alveoli,
airways, and blood vessels, and it results from
incomplete lung development.
 It may be either primary or secondary to intrauterine
processes that affect lung growth, such as congenital
diaphragmatic hernia, and it may be complicated by
recurrent infection and atelectasis.
 At chest radiography and CT, the affected lung appears
small and may be hyperlucent due to oligemia.
 The contralateral lung may appear hyperlucent, a result
of compensatory hyperexpansion.
 The ipsilateral pulmonary artery usually appears
diminutive, and ipsilateral mediastinal shift is present.

36.  Right pulmonary hypoplasia in a 1-week-old
boy. (a) AP chest radiograph shows a
hyperexpanded, hyperlucent left lung and
dextroposition of the heart. (b) Axial contrast-
enhanced CT image shows a small right
pulmonary artery (arrowhead). The left
pulmonary artery (arrow) is normal in caliber.

37.  there is unilateral absence of a central pulmonary artery.
 abnormal development of the sixth aortic arch in utero,
and the affected side typically is opposite the aortic arch.
 More peripheral ipsilateral pulmonary arteries are supplied
by systemic collateral arteries including the patent ductus
arteriosus (PDA), aortopulmonary and bronchial arteries,
subclavian artery, internal mammary artery, and intercostal
arteries.
 Ass. with other cardiovascular anomalies, such as TOF.
 PDA and pulmonary arterial hypertension are associated
with decreased survival during infancy.

38.  At chest radiography and CT:
 ipsilateral lung usually appears small, a finding
likely due to hypoplasia, and the contralateral lung
appears hyperlucent and hyperexpanded.
 I/L shift of the mediastinum and anterior junction
line often is present.
 Other findings:
◦ i/l absent or diminutive appearance of pulmonary hilum,
◦ i/l narrowed intercostal spaces,
◦ occasionally, rib notching.
 Other CT findings:
◦ nonvisualization of the i/l central pulmonary artery,
reconstitution of more peripheral pulmonary arteries from
collateral vessels, and linear areas of opacification
perpendicular to the pleura, a finding thought to represent
transpleural collateral blood vessels.

39.  Proximal interruption of the left pulmonary artery
 PA chest radiograph shows mild hyperexpansion and associated hyperlucency of
the right lung. The mediastinum is shifted to the left, and the aortic arch is right
sided.
 (b) CECT volume-rendered image shows absence of the mediastinal portion of
the left pulmonary artery, with a relative paucity of more peripheral left
pulmonary arterial structures (*). These structures are reconstituted from
collateral vessels, including a PDA (arrow).

40.  also known as hypogenetic lung syndrome or pulmonary
venolobar syndrome
 is a form of partial anomalous pulmonary venous
connection that involves all or a portion of the right lung.
 The anomalous pulmonary vein (the scimitar vein) may
drain into a variety of structures, including the
infradiaphragmatic inferior vena cava (IVC), suprahepatic
IVC, hepatic veins, portal vein, azygos vein, coronary
sinus, and right atrium.
 The ipsilateral lung typically is hypoplastic, and the
affected hemithorax almost always is on the right side.
 The clinical significance- relates in part to the degree of
left-to-right shunting of blood and associated congenital
heart disease.

41.  At chest radiography and CT, the ipsilateral lung
typically appears small, and the contralateral lung
usually is hyperinflated and hyperlucent.
 At radiography, the scimitar vein may appear as a
curvilinear tubular opacity along the border of the
right side of the heart.
 The mediastinum and heart are shifted toward the
affected side (typically the right side), and the
ipsilateral pulmonary hilum may appear small, a
finding due to pulmonary artery hypoplasia or
aplasia.
 Systemic arterialization of the right lung (without
sequestration) also may be present, with the
anomalous artery arising from the abdominal aorta
or a visceral artery.

42.  Scimitar syndrome. (a) AP chest radiograph shows mild
hyperinflation of the left lung with slightly increased vascularity,
a small right lung, and rightward mediastinal shift.
 (b) Axial CECT image in another child with scimitar syndrome
shows mild hyperinflation of the left lung. The right lung and
pulmonary artery (arrowhead) are small, and an anomalous
pulmonary vein (arrow) is seen within the right posterior
hemithorax.

43.  Unilateral congenital pulmonary
lymphangiectasia has also been reported to
be a cause of a unilateral hyperlucent
hyperexpanded lung in neonates.
 A massive central pulmonary embolus may
cause considerable unilateral pulmonary
oligemia, and it also may manifest with a
unilateral hyperlucent hemithorax at
radiography.

44.  In unilateral pulmonary venous atresia, the affected lung typically
appears small and hyperattenuating, a result of pulmonary venous
congestion, and the unaffected lung generally appears relatively
hyperlucent and may be hyperinflated.
 Congenital left pulmonary venous atresia in a 2-day-old boy. Coronal
reformatted CT image shows unilateral pulmonary edema in the left
lung, with interlobular septal thickening (Kerley lines) and relative
hyperlucency of the right lung.

46.  Gas located within the anterior
pleural space on a supine chest
radiograph may have - “large
hyperlucent hemithorax sign”
and most common in neonates.
 The ipsilateral hemithorax may
also appear slightly enlarged.
 This finding should not be
dismissed as a result of artifact
 It may be confirmed with either
a lateral or decubitus
radiograph.

47.  Dependent, layering fluid within
the pleural space may cause the
contralateral hemithorax to
appear hyperlucent, a false
finding.
 The presence of a c/l layering
pleural effusion may be
confirmed by obtaining a lateral
decubitus radiograph (with the
more radiopaque hemithorax
positioned down), which will
depict layering pleural fluid
along the dependent lateral
chest wall,
 or at ultrasonography.
a 9-day-old girl who underwent surgical
repair of TOF and open median sternotomy.
AP chest radiograph shows an apparent
hyperlucent right lung, due to a layering
left pleural effusion. A left apical cap is
seen, as well as fluid tracking along the left
lateral chest wall .

48.  may be either congenital or acquired.
 Congenital diaphragmatic hernias are most commonly left-sided and
posterior in location (so-called Bochdalek hernias). Intraabdominal
structures, including the stomach and small and large intestines, as
well as solid organs, may pass through these diaphragmatic defects
and reside (either partially or completely) within the thorax.
 When gas-filled stomach or bowel loops are present within the
chest, the affected hemithorax may appear hyperlucent.
 Gastrothorax is a rare complication of upper abdominal trauma and
may also manifest as a unilateral hyperlucent hemithorax that
mimics an ipsilateral tension pneumothorax.

49.  Congenital left
diaphragmatic hernia in
a 1-day-old girl.
 Chest radiograph shows
the left mid and lower
hemithorax, which
appear hyperlucent due
to herniation of gas-
filled loops of bowel and
stomach into the left
thoracic cavity
(arrowheads).
 A ng tube is seen within
the intrathoracic
stomach, and the left
lung is hypoplastic (*).

51.  associated with a variety of congenital chest
wall anomalies including
◦ unilateral partial or complete absence of muscles
such as the pectoralis major, pectoralis minor,
latissimus dorsi, serratus anterior, and intercostal
muscles;
◦ ipsilateral rib anomalies such as hypoplasia or
absence of ribs;
◦ mammary tissue hypoplasia or aplasia.
 Scoliosis and upper extremity anomalies such
as syndactyly also may be present.

52.  At chest radiography,
the affected hemithorax
often appears
hyperlucent, an
appearance that mimics
that of radical
mastectomy in adults.
 Both chest radiography
and CT depict absent or
hypoplastic ipsilateral
ribs and scoliosis when
present.

53.  At CT, ipsilateral partial or complete absence of
chest wall musculature is seen.
 Ipsilateral mammary tissue may appear hypoplastic
(compared with the contralateral breast) or
completely absent.

54.  Thoracic spine scoliosis is a rare cause of
unilateral hyperlucent hemithorax .
 Hyperlucency is due to substantial axial
rotation of the spinal curvature, which leads
to asymmetric absorption of the x-ray beam
by the chest wall.

55.  Patient rotation - most common cause.
 The area of hyperlucency is always on the side
toward which the patient rotates (independent of
AP or PA technique) and results from asymmetric
absorption of the x-ray beam by the chest wall .
 Evaluation of the appearance of the ribs,
clavicles, spinous processes, sternal ossification
centers, and sternal wires (when present) on
frontal chest radiographs may help determine the
extent of patient rotation.
 Lateral decentering (positioning the x-ray tube
lateral to the patient’s midline) also may cause a
unilateral hyperlucent hemithorax to be seen.

56.  Hyperlucent right hemithorax resulting from patient rotation in a 2-
week-old boy who underwent cardiac surgery. (a) AP chest radiograph
shows a hyperlucent right hemithorax. The asymmetric appearance of
the ribs and clavicles indicates that the patient is rotated to the right.
Midline sternotomy wires are also displaced to the right. (b) Follow-up
AP radiograph obtained 6 hours later, with the patient in a more
appropriate position, shows no abnormal hyperlucent right
hemithorax.