Congenital Abnormalities of the Thorax

Chapter 2 Congenital Abnormalities of the Thorax



Several congenital abnormalities of the thorax have been described, but most are rare. Classification of these anomalies is difficult because the embryologic basis often is not clearly understood. A classification based on thoracic anatomic structures uses the categories of trachea, bronchi, lung, and pulmonary vasculature. Congenital abnormalities involving the mediastinum are discussed in Chapter 15, and airway anomalies are discussed in Chapter 13.


The diagnosis usually can be established noninvasively by means of standard radiographs, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI). A comprehensive listing of congenital abnormalities of the chest is provided in Box 2-1. In this chapter, congenital abnormalities in adults are emphasized. Those more commonly identified in infancy are discussed in Pediatric Radiology: The Requisites.




TRACHEA


The most common anomalies of the trachea include congenital stenosis, tracheomalacia, congenital tracheobronchomegaly, aberrant tracheal bronchus, and tracheoesophageal fistula.








BRONCHI






LUNGS



Pulmonary Agenesis and Hypoplasia


Pulmonary agenesis is a condition with total absence of the lung parenchyma and the vessels and bronchi distal to the carina. Patients with pulmonary aplasia have a rudimentary bronchus, which ends in a blind pouch without lung tissue or pulmonary vasculature. A decrease in the number or size of airways, vessels, and alveoli characterizes pulmonary hypoplasia. The lesion may be primary, or it may result from several pathogenetic mechanisms that may occur during gestation. These conditions include decreased pulmonary vascular perfusion, oligohydramnios, or compression of the lung by a space-occupying mass within the pleural cavity (e.g., congenital diaphragmatic hernia).


Agenesis, aplasia, and hypoplasia more frequently involve the right lung. In agenesis, the radiograph shows complete absence of an aerated lung in one hemithorax, with pronounced reduction in the volume of that hemithorax and associated shift of the mediastinum to the affected side (Fig. 2-9). There is usually pronounced compensatory overinflation of the contralateral normal lung. Pulmonary hypoplasia has similar findings because of volume reduction; however, there is a small lung on the affected side. In some cases, it may be difficult on standard radiographs to distinguish severe pulmonary hypoplasia from aplasia or agenesis. In such instances, CT may help to identify the absence or presence of the ipsilateral pulmonary artery and bronchus or the presence of a rudimentary bronchus in pulmonary aplasia. CT also can demonstrate rudimentary pulmonary tissue in the base of the hemithorax in patients with severe pulmonary hypoplasia and show a patent bronchus and accompanying pulmonary artery (Fig. 2-10).




Pulmonary hypoplasia must be differentiated from other conditions that can produce a small lung with markedly reduced volume of the hemithorax, including total atelectasis of the lung, severe bronchiectasis with collapse, and advanced fibrothorax due to chronic pleural disease. CT is likely to be diagnostic in these cases.


Feb 28, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Congenital Abnormalities of the Thorax
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