+++
Airway and Lung Parenchyma
+++
Congenital Abnormalities
of the Trachea
++
Tracheomalacia leads to tracheal collapse due to localized or
generalized weakness of the tracheal wall, and respiratory obstruction (see Chapters 371 and 510). The differential diagnosis
includes extrinsic compression of the trachea; intrinsic tracheal
wall disease, such as complete cartilage rings; and luminal problems,
such as tracheal web. Congenital tracheomalacia may be associated with
bronchomalacia, and other abnormalities such as tracheoesophageal
fistula or laryngeal cleft. There is usually early onset expiratory
stridor. The child may become profoundly cyanosed during crying.
Diagnosis is by bronchoscopy, bronchography using small volumes
of water-soluble contrast, or magnetic resonance imaging (MRI).
First treatment is of the underlying cause if feasible. Mild tracheomalacia
needs no active treatment, but the family should be taught cardiopulmonary resuscitation.
Proposed surgical treatments include aortopexy, tracheopexy, and
stenting, but as yet the evidence of benefit is limited.6 Short
malacic segments may be amenable to excision. If surgery is not
thought feasible, or is refused by the family, then ventilatory support
should be considered. Continuous positive airway pressure (CPAP)
while the child is asleep may be sufficient, but if ventilatory
support is required during wakefulness as well, then tracheostomy
must be considered. This is very effective for short-segment tracheomalacia,
but is problematic when the distal trachea is involved. Tracheal
atresia is rare; isolated atresia may be amenable to surgical reconstruction,
but most are fatal. Minor tracheal hypoplasia and other airway abnormalities,
including complete cartilage rings, may be seen in Down syndrome.7
++
Stenosis usually occurs as because of a web in the subglottic
area or just above the carina, although diffuse involvement has
also been recorded. An abnormally long and funnel-shaped trachea
may also occur with complete cartilage rings, which may be associated with
pulmonary artery sling.8,9 This diagnosis may be
confirmed by bronchoscopy, endobronchial ultrasound, MRI, or low
contrast volume bronchography. If the tracheal lumen is small this
may be incompatible with survival. In milder cases, there may be
respiratory distress in the delivery room unrelieved by intubation
or even tracheostomy. Milder cases may require no treatment, and
often tracheal growth keeps pace with the child. Surgery may become
necessary as the child grows, if exercise tolerance is severely
limited. Options include resection or reconstruction of the stenotic
segment, or even tracheal transplant for really severe and complex
cases. The multiplicity of surgical techniques reflects the relatively
poor outcome in the severely symptomatic.
+++
Congenital Abnormalities
of the Bronchial Tree
++
Congenital bronchial stricture occurs predominantly in a main
stem or middle-lobe bronchus and can lead to acute and/or
chronic pulmonary infection. Inflammatory scarring of the congenitally
stenosed bronchus leads to distal suppuration, atelectasis, and
bronchiectasis. Atresia is usually asymptomatic and detected incidentally on
x-ray. The airway may be blocked by a simple membrane, or there
may be a discontinuity. Atresia often results in cystic degeneration
of the lobe distal to the obstruction before birth, as fetal lung
liquid continues to be secreted and cannot drain. Absent bronchus
and bronchogenic cyst may be more common than was once thought (see
below).
+++
Abnormal Bronchial
Origin and Bronchial Branching
++
Bronchi can arise from the gastrointestinal tract. The right
upper lobe bronchus can arise from the trachea (“pig bronchus”).
This is usually of no clinical significance, but may be a cause
of recurrent right upper lobe collapse in an intubated patient if
the endotracheal tube (ETT) is low. The right lower lobe bronchus
may also arise from the left bronchial tree, a so-called “bridging
bronchus.” Whole lung segments may also cross over.
+++
Disorders of
Bronchial Laterality
++
The two most useful determinants of right lung morphology are
the presence of three not, two lobes, and a very short main bronchus
prior to the takeoff of the upper lobe. Mirror-image arrangement
must be distinguished from congenitally small (hypoplastic) right
lung with right sided heart (dextroposition). Mirror-image arrangement
and other forms of heterotaxy10 may be a feature
of primary ciliary dyskinesia, whereas a congenital small lung needs
to have its vascular supply delineated (below). The word isomerism is
so entrenched that it is probably not feasible to replace it with
the term bilateral right lung), which might be
simpler to understand. Nearly 80% of children with right
isomerism, i.e., bilateral right lung, have asplenia and are thus
at risk of overwhelming pneumococcal sepsis. Ivemark syndrome consists
of right isomerism, asplenia, a midline liver, malrotation of the
gut, and a variety of cardiac abnormalities.11 Left
isomerism, i.e. bilateral left lung, is associated with polysplenia
in around 80% of patients. These patients may also have
a midline liver, malrotation of the gut, partially anomalous pulmonary
venous drainage, and cardiac septal defects.12
+++
Disorders of
the Bronchial Walls
++
All or part of the bronchial wall caliber may be too large or
too small. These may present with recurrent infections, steroid
unresponsive wheeze, or stridor. Congenital tracheobronchomegaly
(Mounier-Kuhn syndrome) is characterized by tracheomalacia and greatly
dilated major airways. True congenital bronchiectasis is much rarer
than previously thought.
++
The bronchial lumen may be narrowed by complete cartilage rings.
There may be an associated pulmonary artery sling. A short segment may
require no treatment. If ventilation is critically compromised,
surgical excision or a Z-plasty may be indicated. Congenital bronchomalacia
may be isolated, often with a good prognosis, or associated with
other congenital abnormalities.
+++
Pulmonary Agenesis,
Aplasia (Absent Lung), and Hypoplasia (Small Lung)
++
Bilateral absent lungs is a rare malformation that may occur
in anencephaly. Unilateral absent lung is slightly more common.
Lobar agenesis and aplasia are rarer than complete absence of one lung
and usually affect the right upper and middle lobes together. Pulmonary
hypoplasia (CSL) consists of incompletely developed lung parenchyma connected
to bronchi that may also be underdeveloped dependent upon when the
presumed casual insult took effect in embryogenesis. There are a
large number of causes of CSLs (eTables 507.2, 507.3, and 507.4). Children with complex
malformations, for example unilateral CSL with abnormal vasculature,
may be asymptomatic for long periods despite a formidable list of
abnormalities. Any aortopulmonary collaterals should be occluded.
Long survival, even with an absent lung, is quite possible.
++
++
++
+++
Congenital Cystic
Lesions
++
Numerous pathologic conditions present with cystic changes in
the lung, with acquired lesions outnumbering those that are developmental
in origin. It has been recognized pathologically that bronchial
atresia is a common accompaniment of congenital thoracic malformations
(CTMs). Presentation of these lesions has been discussed above.
This section discusses the pathology. It is usually only after surgical
excision that sensible pathologic diagnoses can be made.
+++
Foregut (Bronchogenic)
Cysts (Clinically, Cystic Ctm)
++
Foregut cysts are epithelial lined sacs in the thorax.
Bronchogenic cysts, distinguished by the presence of cartilage in
the wall are the most common cysts reported in infancy, although many
do not present until adulthood. About 50% are situated
in the mediastinum close to the carina, and less frequently adjacent
to the oesophagus and alongside the tracheobronchial tree. More
rarely, they are found within the lung parenchyma and exceptionally
they are extrathoracic. Foregut cysts are usually single, unilocular,
and more common on the right. They may have a systemic blood supply.
Fistulous connections between cysts and the bronchial tree have
been reported. Malignant transformation is exceptionally rare but
is reported in gastroenteric cysts.
+++
Cystic Adenomatoid Malformation
++
Cystic adenomatoid malformations (CCAMs) encompass a spectrum
of variably sized cysts with differing histology. The reported incidence is
between 1:25000 and 1:35000, although antenatal ultrasound is causing
us to increase estimations of prevalence. Type 0 CCAMs, also termed acinar
dysplasia, are rare, incompatible with life, and typically associated
with other abnormalities. Type 1 is the most common type of CCAM, and
has the best prognosis; cysts are over 2 cm in diameter by definition.
The cystic spaces are lined by pseudostratified ciliated columnar
epithelium and mucus cell hyperplasia is seen in 35% to
50% of cases. Type 2 CCAMs are the second most frequent
type. They generally cause respiratory distress in the first month
of life and may be associated with renal agenesis, cardiovascular
defects, diaphragmatic hernia, and syryngomyelia. Macroscopically,
the lesions are multiple small cysts. Microscopically the cystic airspaces
relate to a relative overgrowth of dilated bronchiolar structures
that are separated by alveolar tissue, which appears comparatively underdeveloped.
Type 3 CCAMs are uncommon and occur almost exclusively in males. They
typically involve and expand a whole lobe, the others being compressed.
Macroscopically, lesions appear solid and not cystic. Microscopically,
there is an excess of bronchiolar structures separated by air spaces
that resemble late fetal lung. Type 4 CCAMs are also very rare and comprise
peripheral thin-walled cysts that are often multiloculated. The
cystic spaces are typically lined by alveolar type I or type II
cells with the intervening stroma being thin and comprising loose
mesenchymal tissue. There is overlap with type 1 pleuropulmonary
blastomas.
+++
Treatment of
Congenital Cystic Lesions
++
If a cystic lesion is causing significant symptoms, usually during
the newborn period, despite medical therapy, then the baby needs surgery.
For all but the smallest, sickest infants, lobectomy (usually thoracoscopic)
is a safe and well-tolerated procedure, with few if any significant
sequelae. Pneumonectomy carries a significant mortality in infancy,
and long-term morbidity, in particular scoliosis, which may worsen
during the pubertal growth spurt.
++
If a previously asymptomatic cystic lesion has become infected,
the lesion should be excised. Other unequivocal indications for
treatment, usually surgery or coil embolization of a feeding vessel,
are respiratory distress and failure to thrive, usually in the newborn
period; high output heart failure due to aortopulmonary collateral
flow; pneumothorax nonresponsive to conventional therapy; infection
of the malformation, or chronic distal infection due to airway compression, and
uncontrolled hemorrhage from the malformation (hemothorax or hemoptysis).2 The
management of the small, asymptomatic congenital thoracic malformation (CTM)
is controversial. Some operate on all but the tiniest malformations,
and others only operate on symptomatic babies. Proponents of neither
view can adduce convincing evidence for their position. If the lesion
is cystic, then it is likely (but unproven) that infection is likely
sooner or later, and prophylactic excision would be recommended
by many.13 It is said that all lesions should be excised
to prevent malignant transformation, but there is little evidence
in favor of this view (see below). Whether an asymptomatic malformation
should be resected to prevent the development of complications,
or to facilitate normal lung growth, is not clear. If the risk of
these lesions becoming infected is unknown, we know even less about
the risk of malignant transformation. Primary pulmonary malignancy
in childhood is very rare, but there are reports of coexistence
of CTM and a variety of primary pulmonary malignancies. Removal
of a CTM cannot prevent the development of malignant disease elsewhere
in the lung,14 implying that the malformation is merely
a marker of generalized increased malignant potential. There is
insufficient evidence on which to base recommendations as to how
to prevent malignancy.
+++
Pretreatment
Investigations in Congenital Cystic Lung Disease
++
If surgery is contemplated, it is essential to delineate the
anatomy of the congenital thoracic malformation (CTM), including
the blood supply. Contrast high-resolution chest computed tomography (HRCT)
gives the best images of parenchymal abnormalities, and is currently
probably the investigation of choice in suspected CTM.
+++
Pulmonary Sequestration
++
The classic definition is tissue that is isolated from normal
functioning lung and is nourished by systemic arteries, although
the separation may be purely vascular. The intrapulmonary variant
is contained within otherwise normal lung parenchyma. The less common
extralobar sequestration is accessory to the lung. Sequestrations
may also connect to the oesophagus or stomach, as well as contain
pancreatic tissue and also may show histologic features of cystic
adenomatoid malformation (CCAM). The etiology is not understood.
Intralobar sequestrations are usually found in the posterior basal
segment of the left lower lobe and extralobar sequestrations beneath
the left lower lobe. About 15% of extralobar sequestrations
are abdominal. The intralobar sequestration is encircled by visceral
pleura and has no pleural separation from the rest of the lobe. The
remainder of the affected lobe and lung is normal, unless secondary
changes such as infection have supervened. More than half the cases
of intralobar sequestration are diagnosed after adolescence, and
symptoms in neonates and infants are uncommon. Extralobar sequestration
is generally detected in infancy because of associated malformations
and affects males four times more frequently than females. Although
much rarer, intralobar sequestrations may also be associated with
other malformations. Treatment of sequestration is surgical excision.
The vascular supply should be carefully delineated by preoperative
investigations, and embolization of aortopulmonary collaterals may
be considered.
+++
Congenital Large Hyperlucent
Lobe (Congenital Lobar Emphysema)
++
Congenital large hyperlucent lobe (CLHL) is a rare condition
that affects the left upper (42%), right middle (35%),
right upper (21%), and lower lobes (2%). The affected
lobe overdistends and displaces adjacent lobes and subsequently the
mediastinum, and may herniate into the contralateral hemithorax.
The condition may be diagnosed antenatally; present as respiratory
distress, often with consequent failure to thrive in infancy; or
be a chance finding on a chest radiograph (CXR) taken later in life.
Clinical features of infantile lobar emphysema are suggestive of
a tension pneumothorax. Usually, a CXR will demonstrate a hyperlucent
lobe with features of compression and collapse of the adjacent lung,
ipsilateral depression of the diaphragm, and mediastinal shift. Bronchoscopy
may reveal causes of intrinsic obstruction and permit the removal
of a foreign body or inspissated secretions, or even provide temporary
relief of symptoms to facilitate surgery.15 The
differential diagnoses is any intrinsic or extrinsic airway cause of
failure of airspace emptying and any cause of loss of lung volume on
the contralateral side including absent lung and lobar or lung collapse
due to bronchial obstruction. Children who are thriving and asymptomatic
require no treatment, otherwise treatment is lobectomy.
+++
Abnormal Connections
between the Bronchial Tree and Other Structures
+++
Tracheoesophageal
Fistula (TOF) and Esophageal Atresia
++
The genetics, associated disorders, diagnosis, and treatment
of tracheoesphageal fistula is discussed in Chapter 392.
+++
Other Abnormal
Connections
++
Rare direct communications between the bronchial tree and congenital
thoracic malformation (CTM), the biliary tract, and the stomach
have been described.
+++
Congenital Abnormalities
of the Pulmonary Arterial Tree
++
Systemic arterial abnormalities can be separated into those of
the bronchial circulation; other pathologic collaterals; and airway compression
by abnormal great vessels, for example a double aortic arch. The
pulmonary capillary bed may be bypassed by direct arteriovenous
communication, or absent, resulting in minimal pulmonary arteriovenous
connections.
+++
Disorders of
Pulmonary Artery Arrangement
++
In general, pulmonary arterial and venous arrangement mirrors
bronchial arrangement. Exceptions include congenital origin of the
left pulmonary artery from the right (pulmonary artery sling), where
the left pulmonary artery traverses the mediastinum compressing
the trachea. There may also be a crossover arterial segment, with
the right upper lobe supplied from the left pulmonary artery, or
complete cartilage rings. Isolated crossover pulmonary artery branches
in the absence of bronchial crossover are occasionally seen (see Chapter 484).
+++
Absent or Small
Pulmonary Artery
++
Absent or small pulmonary artery may be isolated or associated
with other cardiovascular anomalies. Symptoms may not arise until adult life,
and include pulmonary infection or hemorrhage. Congenitally small
unilateral pulmonary artery is usually associated with an ipsilateral
congenital small lung (CSL). Pulmonary arterial stenosis may affect
lobar and segmental vessels as well as the main pulmonary arteries.
Isolated unilateral absence of a pulmonary artery may be asymptomatic,
or there may be infection or bleeding from bronchopulmonary anastomoses.
Anomalous systemic arteries supplying the lung may be associated
with any congenital thoracic malformation (CTM), or even be an isolated
finding.17 They are also found if the pulmonary
artery is absent and may also be part of complex arteriovenous malformations.
One or both pulmonary arteries may take origin from the aorta.18 Bilateral
origin from the aorta is part of the spectrum of common arterial
trunk, and usually will present to the pediatric or fetal cardiologist.
Unilateral origin of a pulmonary artery from the aorta may be an
isolated abnormality, sometimes presenting with persistent tachypnea.
+++
Relevant Congenital
Abnormalities of the Systemic Arterial Tree
++
Vascular ring causes compression of the tracheo-esophageal complex. Presentation
is usually with stridor, or ‘steroid resistant asthma’,
but occasionally dysphagia dominates. (See Chapter 484.)