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Antenatal ultrasound diagnoses many congenital lung malformations, but we now have to decide what to do for a baby affected by an abnormality that may previously have escaped detection. Initial reports described a poor outcome for fetuses with lung masses detected in the second trimester. It is now clear that many lung lesions disappear or regress considerably by term, and the outcome for such fetuses is in general very good. Postnatal regression of lung malformations has also been described. The dilemma in the postnatal period is whether to opt for observation or surgery.

The nomenclature of congenital lung disease may be confusing. For example, sequestration and cystic adenomatoid malformation (CCAM), sometimes assumed to be separate identities, but histologic features of both may be found within the same lesion. There is inconsistent use of nomenclature before and after birth. It is necessary to think in new ways about congenital lung disease. The following principles should be followed1:

  1. 1. What is actually seen should be described, without embryologic or pathologic speculation, which may later be proved wrong. The same clinical appearance (eg, a multicystic mass) may have one of several different histologic appearances when excised. A simple “catch-all” term, congenital thoracic malformation (CTM), is useful for clinical discussions, prior to any pathologic examination.

    2. The description should be in everyday language, avoiding ambiguity. For example, hypoplastic lung could mean a lung that is small but otherwise normal, or small and structurally abnormal; congenital small lung (CSL) is clearer, and avoids assumptions about structure. Congenital lobar “emphysema” is another source of confusion as in adults it implies lung destruction. What is actually seen is a congenital large hyperlucent lobe (CLHL). Throughout this chapter, established terms will be given in brackets after the proposed new term. A summary comparison of old and new nomenclature is given in Table 507-1, and relevant investigations summarized in Table 507-2.

    3. The respiratory system should be described systematically. The lung is formed from 6 “trees”: bronchial, systemic and pulmonary arterial, systemic and pulmonary venous, and lymphatic. There are no known abnormalities of bronchial venous drainage, so in practice, only five trees need to be considered.

    4. Important associated organs (in particular, the heart, great vessels, chest wall, and abdominal contents) should be considered in a systematic manner. Congenital multisystem diseases may affect the lung.

Table 507-1. Comparison of Present and Past Terms Used to Describe Clinical Appearances of Congenital Lung Malformations

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