**4.2. Ultrasound diagnosis**

The ultrasound diagnosis is established on the axial section of 4 chambers of the heart. Unilateral pulmonary hypoplasia determines the mediastinal shift to the hemithorax where the lung is absent and the existing lung is highly hyperechogenic. Usually, unilateral pulmonary hypoplasia (especially the right one) is part of the scimitar syndrome, which is an abnormal venous return in the inferior vena cava (both pulmonary veins are absent and replaced with a collecting vein that drains into the inferior vena cava and which at 3D ultrasound resembles a scimitar). In the case of unilateral pulmonary agenesis, the ultrasound aspect is somewhat similar to the one made in case of CDH, by the mediastinal shift, but there is no abdominal viscera noticed inside the rib cage. The color Doppler can be used to highlight the absence of the pulmonary vascular system. Pay attention to differential diagnosis of CDH with pulmonary compression and CCAM, for unilateral lung agenesis advocates the mediastinal shift to the agenesis side and the enlarged hyperechogenic lung herniated in the contralateral chest through the mediastinum.

delivery. Bilateral lung agenesis is incompatible with life. In the case of the primary bilateral pulmonary hypoplasia or associated with skeletal dysplasia, the importance of a correct diagnosis is not only for the current pregnancy that will evolve to the exitus of the fetus but also for a future pregnancy because skeletal dysplasia may not occur sporadically but exhibit recessive inheritance. In unilateral pulmonary hypoplasia associated with the scimitar syndrome, neonatal ventilation may be required. Fetal MRI may be useful in distinguishing between the pulmonary agenesis and CCAM [23, 24]. At the same time, the exclusion of associated fetal abnormalities can be done by MRI, in particular: ipsilateral upper extremities, mandible, face,

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It comes from the primitive foregut early in the embryogenesis. It contains the columnar ciliary epithelium and the cartridges. They are usually located intrapulmonary but may also be mediastinal [25], or intrapericardial. They may also be located cervical or infradiaphragmatic. They can basically be located anywhere on the tracheoesophageal tract. It is extremely

The diagnosis of bronchogenic cysts can be established on the axial section of the four chambers of the heart. It appears as a unilateral, circumscribed, thin wall lesion (**Figure 13**).

They may rarely be multilocular. The bronchogenic mediastinal cyst can compress the trachea or bronchi so that the distal lung becomes dense and expansive, in this way lending the specific echographic aspect for the cystic adenomatoid malformation [26]. The differential diagnosis includes: CCAM, esophageal duplication cyst, pericardial cyst, duplication cyst and

lymphangioma. In CCAM, the tissue surrounding the cyst is hyperechogenic.

or kidneys. There is no fetal intervention available in pulmonary agenesis.

**5. Bronchogenic cysts**

**5.1. Definition and incidence**

**5.2. Ultrasound diagnosis**

**Figure 13.** Bronchogenic cyst: star—lung mass.

rare.

Bilateral pulmonary hypoplasia is caused by a skeletal dysplasia that is associated with a significant reduction in thoracic volume. Quite rarely, bilateral pulmonary hypoplasia is primary, and it is more commonly secondary to a prolonged oligohydramnios after a long lasting very premature rupture of membrane. The ultrasound diagnosis is also done on the axial section of four chambers view of the heart. The aspect is that the heart fills all the thorax, there is no lung tissue and the rib cage is extremely small. There are nomograms in the literature for thoracic circumference versus gestational age or cardiothoracic ratio.

There is an association of unilateral/bilateral pulmonary agenesis with facial, radial anomalies, genitourinary anomalies, polyhydramnios or oligohydramnios.

The differential diagnosis of unilateral agenesis is done with CDH, CCAM and BPS.