Noncardiac thoracic anomalies

The use of ultrasound in obstetrics has had a significant impact on the field of prenatal diagnosis. Ultrasound imaging has increased our knowledge of normal fetal anatomy and physiology, and has created the ability to diagnose multiple fetal anomalies prenatally, such as congenital diaphragmatic hernia (CDH), congenital cystic adenomatoid malformation (CCAM), bronchopulmonary sequestration (BPS), and fetal hydrothorax (FHT). These thoracic anomalies occur as a result of different embryologic abnormalities; however, through similar pathophysiologic mechanisms, they may potentially have a devastating impact on normal fetal development and perinatal outcome. Each of these anomalies may create a mass effect within the fetal thorax that has the potential to alter normal pulmonary development and produce hemodynamic compromise. A large mass within the fetal thorax may compress the surrounding lung resulting in pulmonary hypoplasia. The contralateral lung may also be affected if the mass is large enough to produce a significant mediastinal shift. Additionally, compression of the fetal heart and great vessels may result in hemodynamic compromise, including the development of fetal hydrops. Polyhydramnios may occur if compression of the mediastinum interferes with normal swallowing or if gastric obstruction occurs following herniation of the stomach in fetuses with CDH. The prenatal diagnosis of these anomalies has led to the recognition of what Harrison et al(61) describe as the "hidden mortality" of these lesions, referring to those pregnancies that result in fetal demise without a prenatal diagnosis or neonatal demise before transfer or evaluation at a tertiary care center. Many of these anomalies had previously remained undiagnosed, resulting in an underestimation of the true incidence of these anomalies and their clinical significance. Prenatal evaluation has allowed for a greater understanding of the natural history of these lesions, and the recognition of prognostic indicators that havevalue in predicting the outcome of these pregnancies. Additionally current imaging techniques may allow for better evaluation of the fetal lungs and the prenatal diagnosis of pulmonary hypoplasia.(18, 19, 77, 96) These patients may now be counseled more accurately concerning the potential outcome of their pregnancy and management options. For a select group of fetuses, these options now include in utero intervention such as thoracocentesis, shunting, and open fetal surgery and tracheal occlusion. This article reviews these noncardiac thoracic anomalies, including the sonographic findings, natural history, and prognosis associated with these lesions, and the optimal antenatal and neonatal management of these pregnancies.