**7.4. Prenatal management**

**7.2. Ultrasound diagnosis**

180 Congenital Anomalies - From the Embryo to the Neonate

**7.3. Prognosis**

**Figure 15.** Bilateral hydrothorax: arrow—hydrothorax.

Effusions can be unilateral or bilateral (**Figure 15**).

The diagnosis of fetal hydrothorax is established on the axial image of the four chambers of the heart, as an anechoic area around the pulmonary tissue which limits the mediastinum.

The hydrothorax aspect is that of a peripheral anechoic space in the thorax, compressing the lung tissue. In the case of large bilateral effusions, the aspect is that of the lungs balloting in the rib cage. At the same time, mediastinal shift and the eversion of the diaphragm occur with the displacement of the heart to the contralateral side and they can cause the disruption of the hemodynamic function and the installation of nonimmune hydrops. If the pleural effusion is part of the nonimmune hydrops, then it is also possible to see the edema of the thoracic subcutaneous tissue. It is important to note that FHT associates with the polyhidramnios in over 50% of cases, either due to a mediastinal shift that causes the compression of the esophagus or

because of an alteration in the production of amniotic fluid by the compressed lungs.

The differential diagnosis is important because it should be determined whether FHT is primary or secondary. Primary hydrothorax is usually a chylothorax and it is unilateral and is a diagnostic of exclusion. However, the fetus with trisomy 21, Noonan syndrome, and Turner syndrome, may present either unilaterally or bilaterally hydrothorax [31]. For secondary hydrothorax, evidence of specific echographic elements for CDH, CCAM, BPS determines the diagnosis. In the case of the fetuses with hydrops, the presence of fetal anemia should be excluded.

The most important element of prognosis is whether fetal hydrothorax is associated with non-immune fetal hydrops, because in this situation the fetal mortality is increased. Other negative prognostic factors are FHT associated with cardiac abnormalities or with central nervous system anomalies. The only positive prognostic factor is the presence of FHT without another associated anomaly or other fluid effusion with another location. Isolated small FHT at the fetus without any other abnormalities, without hydrops or abnormal karyotype, has a favorable prognosis, because the fetus usually tolerates well small effusions [31, 32]. What is important to remember is that 10–25% of the cases of chylothorax can regress spontaneously It is mandatory to determine the karyotype in FHT due to the increased risk of association with chromosomal anomalies. Even if the fetus tolerates small isolated effusions, a serial echographic surveillance is required because small hydrothorax can progress rapidly to large effusions that may have negative hemodynamic consequences. Therefore, ultrasound monitoring is recommended every 1 or 2 weeks, due to the risk of polyhidramnios and preterm delivery. Birth in a tertiary center is recommended.

If FHT was diagnosed before 24 weeks, the therapeutic interruption of the pregnancy is an option. If the fetus with FHT has more than 32 weeks, then the serial ultrasound at one or 2 weeks distance is recommended, but we can also consider thoraco-amniotic shunt. If the fetus has less than 32 weeks we have three options: thoracocentesis, thoracoamniotic shunt, thoracomaternal cutaneous drainage. The initial step is the thoracocentesis and diagnosis for cell count, culture, or the viral culture. In general, thoracocentesis other than for diagnosis is ineffective because after it is done a re-accumulation of the pleural fluid occurs. The rapidity with which the effusion accumulates after the initial puncture is an indicator of the pleural effusion severity. For this reason, pleural cavity decompression is done through thoracoamniotic shunt. Large FHT is drained through thoracoamniotic shunt especially if hydrops is present. Shunting is especially effective if the fetus has less than 32 weeks of gestation [34]. The failure rate for thoracoamniotic shunt is of 26% [34, 35]. Shunt complications are: blockage, migration, fetal death. If a thoracoamniotic shunt is mounted the incidence of survival increases from 10 to 60%.
