**6.1. Definition and incidence**

Congenital high airway obstruction syndrome (CHAOS) occurs due to laryngeal atresia, tracheal atresia, or laryngeal cyst [27]. There are three types of laryngeal atresia: type I-agenesis of glottis, Type II agenesis of larynx, type III-agenesis of both [28]. The laryngeal atresia is difficult to differentiate using ultrasound from tracheal atresia and both are diagnosed based on intrathoracic signs. The exact incidence of this syndrome is unknown, but it is an extremely rare abnormality. The cause of tracheal/laryngeal atresia is not clear, but it appears to be a vascularization deficit during the embryogenic period [29, 30].

**6.4. Prenatal management**

**Figure 14.** CHAOS: dilatation of tracheobronchial tree.

through this procedure [29].

**7. Fetal hydrothorax**

**7.1. Definition and incidence**

Karyotyping is not indicated because the risk of chromosomal abnormalities is low. The ultrasound should also focus on the exclusion of structural heart or kidney abnormalities. Delivery should take place in a tertiary center. The only option that exists to save a fetus with CHAOS is the EXIT procedure (ex utero intrapartum treatment). So far, only 9 cases have survived

Thoracic Anomalies

179

http://dx.doi.org/10.5772/intechopen.71959

Fetal hydrothorax (FHT) represents the accumulation of fluid in the pleural cavity, between the parietal and the visceral pleura. It can be unilateral or bilateral. It can be isolated or in the

The incidence is not specified given the variability of the causes, but in the antenatal period, the secondary causes of hydrothorax are more common [31]. The causes that can lead to the occurrence of fetal hydrothorax are multiple: congenital infection (parvovirus, TORCH), isoimmunization, congestive heart failure, Down syndrome, Turner syndrome. Primary FHT is called chylothorax. Secondary FHT usually appears secondary to chromosomal, cardiac, gastrointestinal and infectious abnormalities. FHT generally precedes the installation of fetal hydrops. The appearance of primary FHT is due to a structural defect in the lymphatic system: the obstruction of bronchomediastinal trunks to the venous system, congenital absence of the thoracic duct, congenital hypoplasia of the pulmonary lymphatic vessel [31, 32]. It is a diagnostic of exclusion. In general, primary FHT occurs as a result of the obstruction of secondary lymphatic drainage to a heterogeneous group of developmental defects of the lymphatic system. Unilateral FHT may happen due to a unilateral pathological process such as: congenital diaphragmatic hernia, cystic adenomatoid malformation, pulmonary hypoplasia.

context of a generalized hydrops, or associated with other fetal abnormalities.

### **6.2. Ultrasound diagnosis**

The ultrasound diagnosis is done on the four-chamber axial section. It is noted that both lungs are hyperechogenic, large in size, flattening the diaphragm due to the large volume of the lungs, the heart appears smaller due to the compression exerted by the lungs, the axis of the heart is zero, the dilatation of the tracheobronchial tree can be seen by the accumulation of liquid at its level (**Figure 14**).

On the coronal section, the dilated trachea and bifurcation of this, as well as the diaphragmatic flattening, can be better emphasized. The differential diagnosis of CHAOS does not have what entity to do, because it is a unique anomaly. At most, bilateral CCAM can be considered in the differential diagnosis, but bilateral CCAM is very rare and it does not present a severely increased volume of both lungs.

#### **6.3. Prognosis**

This anomaly is fatal. It may be part of the Fraser syndrome [29, 30], which includes: laryngeal atresia, renal agenesis, oligoamnios, microphthalmia, syndactyly, polydactyly. The prognosis is even more severe because the recessive autosomal is transmitted. The risk of chromosomal anomalies is low.

**Figure 14.** CHAOS: dilatation of tracheobronchial tree.

### **6.4. Prenatal management**

**5.3. Prognosis**

**5.4. Prenatal management**

178 Congenital Anomalies - From the Embryo to the Neonate

**(CHAOS—laryngeal atresia)**

**6.1. Definition and incidence**

**6.2. Ultrasound diagnosis**

liquid at its level (**Figure 14**).

**6.3. Prognosis**

anomalies is low.

severely increased volume of both lungs.

One of the few negative prognostic factors is the size of the mass.

birth is recommended to take place in a tertiary center.

**6. Congenital high airway obstruction syndrome** 

vascularization deficit during the embryogenic period [29, 30].

The presence of bronchogenic cysts does not cause the death of the fetus in utero [25, 26]. It is not recommended to perform karyotyping because the risk of associated chromosomal abnormalities is extremely low. There is, however, the risk of an emergency intubation at birth, so

Congenital high airway obstruction syndrome (CHAOS) occurs due to laryngeal atresia, tracheal atresia, or laryngeal cyst [27]. There are three types of laryngeal atresia: type I-agenesis of glottis, Type II agenesis of larynx, type III-agenesis of both [28]. The laryngeal atresia is difficult to differentiate using ultrasound from tracheal atresia and both are diagnosed based on intrathoracic signs. The exact incidence of this syndrome is unknown, but it is an extremely rare abnormality. The cause of tracheal/laryngeal atresia is not clear, but it appears to be a

The ultrasound diagnosis is done on the four-chamber axial section. It is noted that both lungs are hyperechogenic, large in size, flattening the diaphragm due to the large volume of the lungs, the heart appears smaller due to the compression exerted by the lungs, the axis of the heart is zero, the dilatation of the tracheobronchial tree can be seen by the accumulation of

On the coronal section, the dilated trachea and bifurcation of this, as well as the diaphragmatic flattening, can be better emphasized. The differential diagnosis of CHAOS does not have what entity to do, because it is a unique anomaly. At most, bilateral CCAM can be considered in the differential diagnosis, but bilateral CCAM is very rare and it does not present a

This anomaly is fatal. It may be part of the Fraser syndrome [29, 30], which includes: laryngeal atresia, renal agenesis, oligoamnios, microphthalmia, syndactyly, polydactyly. The prognosis is even more severe because the recessive autosomal is transmitted. The risk of chromosomal Karyotyping is not indicated because the risk of chromosomal abnormalities is low. The ultrasound should also focus on the exclusion of structural heart or kidney abnormalities. Delivery should take place in a tertiary center. The only option that exists to save a fetus with CHAOS is the EXIT procedure (ex utero intrapartum treatment). So far, only 9 cases have survived through this procedure [29].
