Congenital anomalies of the fetal chest typically consist of lung lesions that are echogenic on ultrasound. These lesions comprise congenital pulmonary airway malformations (CPAM), bronchopulmonary sequestrations (BPS), bronchial atresia, bronchogenic cysts, congenital lobar emphysema, and congenital high airway obstruction syndrome (CHAOS). CPAM and BPS account for a majority of these anomalies. Although rare, the apparent incidence of these echogenic lung lesions has increased recently, with CPAMs now occurring at a rate of 0.94 per 10,000 live births. This increase is likely a product of the improved resolution of ultrasound equipment, and the increasing uptake of routine fetal anomaly scanning in the second trimester.
In utero, fetal echogenic lung lesions can result in mediastinal shift, fluid collections and hydrops. Following birth, they can cause substantial neonatal respiratory compromise. Determining the type of lesion prenatally can be challenging, even with complementary imaging such as MRI scanning, and the final histopathological diagnosis ñ where available ñ is often different to that suspected prior to birth. Of greater importance to prospective parents, however, is the likelihood of a favourable outcome, and the need for fetal intervention and/or intensive neonatal care. A range of sonographic predictors has been proposed for this purpose, but the best studied index is the CPAM-volume ratio ñ the ratio of the volume of the lesion (calculated as a prolate ellipse) to the fetal head circumference, to normalise for gestation.
This presentation will review the performance of the CVR in the prediction of a range of fetal and neonatal concerns, including in a series from the author's own institution. It will also compare this index with other predictors, none of which has shown sufficient utility to replace the CVR at this stage. It will conclude with suggestions regarding future research in this field.