Educational Aims
The reader will come to appreciate:
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Congenital lung and lower airway abnormalities are rare but if not diagnosed can have significant consequences.
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These lesions frequently have associated abnormalities, which will complicate their management.
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Bronchoscopy has an important role both in the diagnosis, and intra- and post-operative management.
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Interventional bronchoscopy has a role to play especially in congenital airway abnormalities.
Abstract
Congenital lung and lower airway abnormalities are rare, but they are an important differential diagnosis in children with respiratory diseases, especially if the disease is recurrent or does not resolve. The factors determining the time of presentation of congenital airway pathologies include the severity of narrowing, association with other lesions and the presence or absence of congenital heart disease (CHD). Bronchoscopy is required in these cases to assess the airway early after birth or when intubation and ventilation are difficult or not possible. Many of these conditions have associated abnormalities that must be diagnosed early, as this determines surgical interventions. It may be necessary to combine imaging and bronchoscopy findings in these children to determine the correct diagnosis as well as in operative management. Endoscopic interventional procedures may be needed in many of these conditions, ranging from intubation to balloon dilatations and aortopexy. This review will describe the bronchoscopic findings in children with congenital lung and lower airway abnormalities, illustrate how bronchoscopy can be used for diagnosis and highlight the role of interventional bronchoscopy in the management of these conditions.
Introduction
Congenital lung and lower airway abnormalities are rare but are an important differential diagnosis in children with respiratory diseases especially if the disease is recurrent or not resolving.
Some lesions cause severe symptoms shortly after birth while others may not present for years.
The latter lesions are often not diagnosed in childhood and present in adults as episodes of recurrent pneumonia or malignancies . In the developing world there is limited access to antenatal ultrasounds and congenital lesions will only be diagnosed much later or once they have become complicated or infected .
The aim of this review is to describe the bronchoscopic findings in children with congenital lung and lower airway abnormalities, how bronchoscopy can be used for diagnosis and the role of interventional bronchoscopy in the management of these conditions.
Presentation of congenital lesions
The lesions which typically present in the neonatal period are congenital cystic adenomatoid malformations (CCAMs) and diaphragmatic hernias because they are space occupying . The factors determining the time of presentation of congenital airway pathologies include the severity of narrowing, association with other lesions and the presence or absence of congenital heart disease (CHD). In cases of difficult and shallow intubations in neonates, congenital airway abnormalities should be considered.
Congenital lesions in infants and older children will present with recurrent pneumonia or non-resolving pneumonia that is localized to the same region . Congenital abnormalities have been reported in up to 45% of cases with persistent wheeze and not responding to asthma treatment in bronchoscopy studies . Vascular compression of the airways was observed in 13%-26% of children who underwent bronchoscopy for persistent wheezing, stridor and apnoea .
If the chest X-ray was never normal it makes the diagnosis of a congenital lesion more likely. Solid lesions may cause more airway compression compared to cystic lesions which can cause mediastinal shift. Chest X-ray findings, such as lack of visibility, narrowing, abrupt discontinuity, displacement of bowing, abnormal branching and focal unilateral overinflation may indicate airway pathology.
Bronchography enables the assessment of both the trachea and the more distal bronchi. Performed in real time with the infant spontaneously breathing, the airways are assessed throughout the respiratory cycle . Bronchography can be performed by injecting isotonic non-ionic contrast down the working channel of a flexible bronchoscope .
Echocardiography needs to be performed before airway surgery and cardiac lesions may have to be corrected at the same time.
Contrast swallow studies are helpful in identifying different types of vascular compression. There are 4 characteristic patterns: Anterior tracheal and posterior oesophageal indentations indicating double aortic arch (DAA); normal tracheal and posterior oesophageal indentation indicating aberrant subclavian artery; posterior tracheal and anterior oesophageal indentation indicating left pulmonary artery (LPA) sling and anterior tracheal compression indicating innominate arterial compression .
Bronchoscopy findings of congenital lung/lower airway lesions ( Table 1 )
The airway is frequently involved in congenital lung abnormalities, either as the primary pathology or secondary due to external compression of the lumen.
| BRONCHOSCOPY FINDINGS | |||
|---|---|---|---|
| Diagnostic | Interventional | ||
| AIRWAY AGENESIS/STENOSIS | Tracheal agenesis |
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| Bronchial agenesis |
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| Bronchial atresia |
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| Hypoplastic right lung |
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| Tracheal stenosis |
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| AIRWAY BRANCHING ABNORMALITIESH | Tracheal bronchus (TB) |
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| Bridging bronchus (BB) |
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| Heterotaxy syndromes | |||
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| Scimitar syndrome |
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| AIRWAY FISTULA | Laryngotracheoesophageal cleft |
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| Congenital tracheo-oesophageal fistula (TOF) |
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| Congenital broncho-oesophageal fistula (BOF) |
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| EXTERNAL AIRWAY COMPRESSION | Bronchogenic cyst (BC) |
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| Foregut duplication cysts |
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| Vascular Compression | |||
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| OTHERS | Interrupted aortic arch (IAA) |
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| Right sided aortic arch (RAA) |
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| Absent pulmonary valve |
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| Horseshoe lung |
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| Mediastinal mass causing airway compression |
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| Tracheobronchomalacia (TBM) |
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| Congenital lobar emphysema (CLE) |
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Bronchoscopy has an important role in the diagnosis of airway pathology, intra- and postoperative management, and long-term follow-up . To evaluate both upper and lower airways, rigid and flexible bronchoscopy should be combined in more complex cases. For example, the role of bronchoscopy in both anterior and posterior aortopexy has increased. Bronchoscopy is used to guide the improvement of airway size and stitches are inserted under bronchoscopic vision .
In cases of difficult intubation and ventilation, bronchoscopy is essential to exclude or confirm congenital airway pathology.
Airway agenesis/stenosis
Tracheal agenesis
Tracheal agenesis (TA) is a rare and lethal anomaly in which the trachea is partially or completely absent with inability to maintain airflow between the larynx and the bronchi. Affected children cannot be intubated and the oesophagus will be inadvertently intubated, allowing ventilation via a tracheo-oesophageal fistula (TOF) .
Three types have been identified: Type 1, the proximal trachea is absent, and a short distal trachea is present, connected to the oesophagus via a TOF; Type 2, most of the trachea is absent with a short carina dividing into right and left bronchi and usually, but not always a TOF, and Type 3, the right and left bronchi arise separately from the oesophagus .
Bronchoscopy findings: An absent or very short trachea, tracheobronchial stenosis and TOF. Interventional bronchoscopy involves endoscopic intubation at birth with an endotracheal tube (ETT) inserted into the oesophagus. In children with prenatal diagnosis, the ex-utero intrapartum treatment (EXIT) procedure can be done with either rigid or flexible bronchoscopic intubation.
Bronchial agenesis ( Fig. 1 )
Bronchial agenesis/aplasia/hypoplasia comprises a spectrum of congenital pulmonary malformations with either absent or rudimentary development of a segmental or lobar bronchus and associated pulmonary parenchyma .
Bronchial agenesis is the complete absence of a bronchus, associated lung parenchyma and pulmonary artery (PA), more often on the left side, resulting in cardiomediastinal shift to that side with overinflation of the contralateral lung. Unilateral pulmonary agenesis is associated with other anomalies, including CHD, pulmonary sling, other PA anomalies, anomalous origin of aortic arch great vessels, oesophageal atresia, tracheal stenosis, and lung and vertebral anomalies .
Bronchoscopy findings: Diagnostic bronchoscopy may indicate only one main bronchus and no carina; vascular compression and airway stenosis may be present, while in aplasia, a blind ending bronchus is visible, and the remaining bronchial tree is rotated. Interventional bronchoscopy should be performed with an ETT if airway stenosis is present.
Bronchial atresia
Bronchial atresia is due to focal interruption of a lobar, segmental, or subsegmental bronchus with associated peripheral mucus impaction (mucocele) and hyperinflation of the obstructed part of the lung .
Computed tomography (CT) can be used to diagnose atresia if a mucus plug (mucocele) is found distal to the atresia with a local decreased attenuation of the hyperlucent region.
The apicoposterior segmental bronchus of the left upper lobe (LUL) is most often involved, followed by segmental bronchi of the right upper, middle, and lower lobes .
The mucus plug develops due to the accumulation of mucus in the patent distal bronchus and the hypodense region due to hyperinflation of the excluded lung parenchyma by collateral ventilation through the pores of Kohn, bronchoalveolar channels of Lambert and interbronchiolar channels .
Bronchoscopy findings: A blind ending bronchus on bronchoscopy is pathognomonic but is not always found. Bronchoscopy may be needed to exclude other possible pathologies with intraluminal obstruction by benign or malignant processes and infections.
Hypoplastic lung ( Fig. 2 )
Hypoplastic lung occurs due to fewer branching generations of the airways, with decreased number of acini and alveolar size . Right sided hypoplasia is much more common than left sided lesions.
Bronchoscopy findings: Hypoplastic right lung has a normal carina but absent right upper and right middle lobes (RMLs).
Tracheal stenosis ( Figs. 3–5 )
Congenital tracheal stenosis (CTS) is an abnormality characterized by the presence of complete tracheal rings along the stenotic segment, creating a fixed narrow tracheal lumen. Short-segment stenosis typically results in an hourglass shape (this type can also be caused by a tracheal web), while long-segment stenosis may result in a so-called “stovepipe trachea” or, if less severe, in a so-called funnel- or carrot-shape (“rat-tail trachea”).
Symptoms are associated with the severity more than with the length of the stenosis. CTS is associated with several other lesions including tracheal bronchus (TB), other airway/lung anomalies as well as pulmonary sling, CHD and H-type TOF. Long-segment tracheal stenosis is strongly associated with type 2 pulmonary sling, occurring in 2 out of 3 cases .
Lung abnormalities, including hypoplastic or even absent lung (usually right sided), bronchogenic cyst, pulmonary sequestration, scimitar syndrome, and gastrointestinal anomalies may also be present .
CT or magnetic resonance imaging (MRI) are essential to study associated vascular malformations.
Slide tracheoplasty is the surgical technique of choice for long-segment tracheal stenosis.
Bronchoscopy findings: The gold standard for the diagnosis and assessment of severity of CTS is rigid and flexible airway endoscopy. In severe cases, even an ultrathin flexible bronchoscope cannot be passed through the stenosis. Bronchoscopy can be used to determine the presence of solid rings, and the length and diameter of the stenosis. .
Associated vascular compression needs to be identified, especially type 2 LPA sling which causes compression of the distal trachea close to the carina with compression of both the anterior and posterior wall. The LPA runs from around the anterior and upper wall of the left main bronchus (LMB) and continues to the LUL bronchus forming a drop like narrowing with the narrowest part at the medial wall. Airway abnormalities associated with the type 2 pulmonary sling include: separate right upper lobe (RUL) bronchus or diverticulum at the normal carinal level resembling a TB, long-segment airway stenosis, low horizontal pseudo-carina, and bridging right bronchus arising from the left bronchus .
In type 1 pulmonary sling, the airway is usually not stenotic, but the right main bronchus may be compressed by the sling or be malacic, resulting in air trapping in the right lung. A TB may be present, and the carina is at the normal level .
Additional associated pathologies include CHD causing vascular compression of the airways, mainly the LMB, and TOF and laryngeal cleft.
Intraoperative bronchoscopy may be required to determine the beginning and end point of tracheal stenosis and rule out alternative sources of vascular compression.
Postoperative bronchoscopy is needed to evaluate the airway reconstruction and determine granulation tissue formation. Balloon dilation with or without laser treatment is regularly needed to manage restenosis and granulation tissue formation .
Airway branching anomalies
Tracheal bronchus ( Fig. 6 )
Tracheal bronchus is defined as an abnormal bronchus originating from the lateral wall of the trachea and has been found in 0.9–1.9% of bronchoscopies . There is a 13-fold increase in the incidence of a TB in children with CHD. Trisomy 21 is frequently associated with a TB . A TB is almost always found on the right side but occasionally also on the left or even bilateral, especially in the context of right isomerism . Ruchonnet-Metrailler et al. have reported that in 61.5% of patients with TB other associated anomalies were present, which included syndromic abnormalities (21%), CHD (19.2%) and tracheal stenosis (14%) .
