Causes of Fetal Hydrothorax
Fetal pleural effusions may be primary and occur in isolation or as part of FH. Primary effusions are usually chylous and may be unilateral or bilateral.
· Immune hydrops- Usually associated with Rh (D) sensitization. Fetal ascites might appear before pleural effusion and skin edema
· Non-immune hydrops- The overall mortality ranges from 50 to 98%. PH is a frequent accompaniment.
· Chylothorax- Chylothorax has been seen in association with diffuse congenital lymphangiomatosis, pulmonary lymphagiectasis, congenital lymphedema, diffuse hemangiomas and chylopericardium.
· Diaphragmatic hernia- Diaphragmatic hernias are the most frequently encountered intrathoracic masses diagnosed in utero. The bowel, liver, spleen or kidney may be seen within. A left sided hernia usually contains the stomach.
· Cystic adenomatoid lung- Lesion usually unilateral but typically involves one lobe or segment. Classified into type I cysts 3—7 cm, type II cysts <1.5 cm and type III cysts so small that they are not discernible on US. Pleural effusion occurs as part of hydrops.
· Pena-Shokier syndrome- Prenatal US may reveal PH, FH, skeletal dysplasias, restricted limb movement, fixed flexion deformity of limbs, absent stomach bubble and kyphosis of the thoracic spine.
· Down's syndrome- The syndrome is associated with IUGR, CNS anomalies, cardiac defects, bowel atresias, craniofacial anomalies and limb abnormalities. Ultrasound abnormality is currently only detected routinely in approximately 20—30% of cases.
· Turner's syndrome- Prenatal sonographic findings include cystic hygroma, FH, small for gestational age, hiatus hernia and esophageal duplication.
· Noonan's syndrome- Associated with limb, rib and vertebral anomalies and lymphatic abnormalities, including pulmonary lymphangiectasis and nuchal cystic hygroma.
· Cardiac failure- May be related to structural defect, fetal cardiac arrythmias or cardiomyopathy. Cardiac failure may occur in conjunction with FH.
· Fetal hypoalbumniemia- Usually causes bilateral pleural transudates. The low albumin level may be a part of generalized hypoproteinemia secondary to congenital nephrosis (inherited or as a result of CMV infection or renal vein thrombosis).
· Cystic hygroma- Fetal pleural effusions have been observed with cystic hygromas, with no associated chromosomal anomalies.
· Pulmonary hypoplasia- This may occur as a primary anomaly but is usually secondary to pressure on the developing lung. Several causes have been implicated.
· Transitory bilateral isolated benign effusions- There are several reports of spontaneous resolution of pleural effusions, particularly those diagnosed in the second or early third trimester.
· Intrauterine viral infections- Usually associated with parvovirus infection.
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