Foreign bodies in the airway of a 14-month-old patient with a history of penetration syndrome. Chest x-rays obtained on inspiration (a) and expiration (b) show greater transparency in the right lung. On expiration, air trapping in the right lung is evident and is due to the valve mechanism, which determines a mass effect of that lung and displacement of the heart and mediastinum to the left. The air-trapping area excludes the right upper lobe, which is displaced cephalad (arrow). This is indicative of the presence of a foreign body in the right intermediate bronchus, which was confirmed by fiberoptic bronchoscopy. The foreign body (a peanut) was later extracted
The standard radiography study should include anteroposterior and lateral projections. Lateral projections that show thickening of the epiglottis and the aryepiglottic folds suggest acute epiglottitis (Fig. 11.2), while increased thickness of the soft retropharyngeal and prevertebral tissue suggests inflammation at this level (a retropharyngeal abscess).
The upper airway can be evaluated precisely by CT, including tridimensional and multiplane reconstructions, especially in cases of acquired or congenital stenosis (Fig. 11.3) or extrinsic compression of the airway by vascular rings (Figs. 11.4 and 11.5). CT can characterize a cervical mass and its relationship to other structures—for example, in situations where the mass is compressing the airway. It is also the most sensitive method for detecting calcification.
CT is usually a good complement to fibroscopy in the study of a congenital stridor and subglottic hemangioma (Fig. 11.6). MRI is also useful in assessing cervical masses because of its contrast resolution, especially when a vascular component is suspected.
The Lung Parenchyma
Congenital bronchopulmonaryanomaliesare common and are composed of a heterogeneous group of anomalies that affect the pulmonary parenchyma, its vascularization, and the lower airway. More than one anomaly can coexist (hybrid forms), and their clinical presentation is variable. They have been classified in different ways by different authors—in particular, according to their anatomy and pathogeny.
A simple classification considers two types: (1) focal malformations(congenital pulmonary hyperinsufflation, bronchial atresia, simple intrapulmonary cysts, congenital pulmonary airway malformation (CPAM), pulmonary sequestration, and an irrigation system congenitally isolated from a normal lung segment); and (2) adysmorphic lung(pulmonary aplasia–hypoplasia complex, lobar agenesis–hypoplasia).
Imaging studies are fundamentalfor diagnosis, and several methods can be used.
Congenital Pulmonary Hyperinflation
Previously called congenital lobaremphysema, this condition is characterized by progressive overdistension of one (or sometimes two) pulmonary lobes without destruction of the alveolar walls. Most often the upper lobes or the right middle lobe are compromised. In the first days of life there is pulmonary fluid trapped in the compromised lobe, so on a chest x-ray this appears opaque and enlarged, with a mass effect on the heart and mediastinum. As vascular and lymphatic reabsorption progresses, the compromisedlobe is aerated. It presents a reticular pattern and later a typical pattern of a hyperinflated lobe with reduced density. The pulmonary vessels are markedly attenuated, but there is no alteration in their structure. These alterations are best demonstrated by CT, which can confirm the diagnosis, determine with certainty the compromised lobe or lobes, and differentiate between this lesion and other pathologies such as CPAM (Fig. 11.7). Most patients become symptomatic in the neonatal period.
Bronchial atresia is characterizedby proximal obliteration of a bronchial segment but with preservation of distal structures. The air enters the affected lung through the collateral canals, producing hyperinflation and air trapping. In turn, bronchial mucus secretions accumulate at the site of obstruction, producing mucosal and mucocele impaction. In most cases, only one segment is affected—usually the upper left lobe—and the condition may be associated with other anomalies. Segmental focal air trapping during exhalation can be observed on a chest x-ray, accompanied by a central tubular orrounded appearance of the mucocele. CT shows segmental pulmonary hyperinsufflation and mucosal impaction signs in much more detail (Fig. 11.8).
Isolated or Single Congenital Chest Cysts
This group includes isolated congenital cysts located in the mediastinum or the pulmonary parenchyma (bronchogenic cysts, duplication cysts, or pleuropericardial cysts). Around 85% of such cysts are located in the mediastinum, and the remaining 15% are located within the lung parenchyma. Mediastinal cysts are most often located in the subcarinal region, while pulmonary cysts are most often found in the lower lobes. The cysts contain mucus fluid and may contain air when there is communication with the airway (Figs. 11.9 and 11.10). The cysts sometimes have calcified walls and can also be associated with other anomalies such as pulmonary sequestration or congenital pulmonary hyperinflation.
Congenital Pulmonary Airway Malformation
Previously called a pulmonary cystic adenomatoid malformation, CPAM is a rare anomaly in development of the lower respiratory tract and branching of the tracheobronchial tree, with hamartomatous formations of distal pulmonary tissue. Histologically, it is characterized by adenomatous proliferation of bronchial-type structures and formation of macro- and microcysts coated with columnar or cuboidal epithelium, with no cartilage or bronchial glands. The different types of CPAM arise from interruption of development at different levels of the tracheobronchial tree and at different stages of pulmonary development. These malformations have been classified into five subtypes according to their clinical, radiological, and histological aspects. The most common (representing 70% of cases) is type I CPAM, which is composed of several cysts of variable size, with at least one being dominant (>2 cm) (Fig. 11.11). Type II is composed of smaller uniform cysts ≤2 cm in diameter and represents 15–20% of cases. Around 10% of cases are type III, which is composed of microcysts, all <0.5 cm in diameter, generally with one lobe completely compromised. Type IV is very rare and consists of one or more very large cysts that are not coated by epithelium and that compromise a pulmonary lobe. Finally, type 0 is an extremely rare and lethal form of CPAM in which lung development fails completely. All types have arterial irrigation and normal venous drainage, and the radiological aspect depends on the type of lesion, the age of the patient, and the presence or absence of complications such as infection.
The clinical picture variesaccording to the patient’s age, the size of the lesion, and whether there are associated anomalies or complications. Patients may present respiratory distress during the neonatal period or remain asymptomatic for variable periods of time. This condition may also appear as recurrent pneumonia; sometimes it appears as an incidental finding or may be detected in routine prenatal ultrasound examinations.
Types I and II can grow progressively with time, communicate with the airway, and fill with air. According to the type of CPAM, a chest x-ray shows areas of greater or lesser lung transparency, with a mass effect on other chest structures, which can be confused with congenital pulmonary hyperinflation or a diaphragmatic hernia.
Chest CT is fundamental in diagnosis because it not only enables characterization of lesions and shows their location and extension, but also allows them to be differentiated from other diseases. Differential diagnosis for CPAM should include pleuropulmonary blastoma, particularly for type IV.
Pulmonary sequestration is a congenital anomaly characterized by an aberrant pulmonary tissue mass that does not have a normal connection with the tracheobronchial tree or pulmonary arteries. It is usually irrigated by an arterial anomaly that originates directly from the aorta with venous drainage through the azygos system, pulmonary veins, or inferior vena cava. It normally appears as pneumonia, although (depending on its size) it can also appear as a chest mass that causes respiratory distress in newborns.
Pulmonary sequestration is most often found in the basal segments of the lower lobes, particularly in the medial zone of thelower left lobe. It has traditionally been divided into two types: intralobar and extralobar. In the former, sequestration is contained within the adjacent lobe, with which it shares its pleural covering and venous drainage, normally through the pulmonary veins. Extralobar sequestration is most often located between the lower lobe and the diaphragm, and has its own pleural covering. Around 90% of cases are located on theleft side, and the venous drainage is commonly via the azygos system.
The clinical picture is diverse. Mostcases of intralobar sequestration involve a history of recurrent focal pneumonia, but some of them appear as an incidental finding, particularly in newborns and infants. Extralobar sequestration is most often diagnosed during the first 6 months of life with clinical manifestations such as dyspnea, cyanosis, and difficulty feeding. It can be associated with other anomalies such as pulmonary hypoplasia, a horseshoe lung, CPAM, a bronchogenic cyst, a diaphragmatic hernia, or cardiovascular anomalies such as an arterial trunk and total anomalous pulmonary venous drainage.
The radiological aspect of intralobar sequestration depends on the degree of aeration and on the presence or absence of associated infection. Nonaerated opacity is a common finding on a chest x-ray (Fig. 11.12). Mixed opacity is evident after recurrent or chronic infections, with air and sometime fluid levels in their cavities. Newborns with extralobar sequestration typically show persistently dense images in theposterolateral aspect of the thorax, normally on the left side.