USA Surgery Today

Fetal hydrothorax can be identified in up to 1:15,000 pregnancies by prenatal US at large referral centers (60:Zebeta). Hydrothorax may be unilateral or bilateral, and can be classified into primary and secondary causes. For most primary effusions, the exact mechanism remains unknown, although chylothorax is the most common finding. Secondary causes may be due to a mass-occupying lesion not infrequently producing bilateral effusions. Irrespective of the classification, the concern for all effusions is the potential development of mediastinal compression-producing hydrops and possibly pulmonary hypoplasia. Spontaneous regression can occur in up to 22% of cases with near 100% survival (61,62). The overall mortality for the untreated fetal effusion is 35% to 53%.

Clearly, the most ominous finding is that of hydrops with up to 76% mortality. Serial prenatal US has shown that unilateral effusions identified in the second trimester and not associated with polyhydramnios or hydrops have the best overall prognosis. The management of fetal hydrothorax depends on the size of the effusion, the presence of any identifiable underlying cause, and the presence of hydrops. Small effusions can be followed sonographically and adequately addressed postnatally. Large effusions or those that increase over time may warrant in utero decompression in order to avoid hydrops and potential pulmonary hypoplasia. The response to fetal thoracentesis is short lived because of the rapid reaccumulation of fluid, although it may be a useful temporizing tool late in gestation. Thoracoamniotic shunts are effective, but have failure rates of up to 26% due to problems with occlusion and dislodgement from the fetal hemithorax (59:Zebeta). Most fetuses with a prenatally identified hydrothorax can be optimally managed by planned delivery at a tertiary care center that can offer comprehensive neonatal care for respiratory distress including ECMO support.