Fetal Cystic Intrathoracic Masses
· Pleural effusions- These appear anechoic and normally conform to the thoracic/diaphragmatic contours.
· Teratomas- These pericardial tumors, which may rarely be malignant, may present as pendunculated cystic masses. They may occasionally calcify, and are often associated with pericardial effusions.
· Bronchogenic cyst- This may be unilocular or multilocular, closely related to the trachea or main bronchus and may communicate with the tracheobronchial tree.
· Diaphragmatic hernia- Diaphragmatic hernia is associated with various chromosomal abnctmalities including trisomies 13, 18 and 21. The reported incidence of chromosomal anomalies in prenatal series is 20—30%. Other associated abnormalities include CHD (9—23%), neural tube defects (28%) and spinal defects. US may reveal polyhydramnios and visualization of abdominal viscera within the thorax. A unilateral pleural effusion may be present. Characteristically, a fluid filled mass is seen behind the left atrium and ventricle, mediastinal shift is variable. Real time sonography may reveal bowel peristalsis within the thorax. Solid organs such as the spleen and liver may herniate into the thorax mimicking a solid lung or intrathoracic mass. A clue to liver herniation may be the presence of the gallbladder within the thorax. An associated finding is a reduction in abdominal circumference. Congenital diaphragmatic hernias are unilateral in 97% and usually on the left.
· Pericardiac cyst- This may be unilocular or multi- cystic, usually attached to the pencardium overlying the right heart border, or rarely presents at the right costophrenic angle.
· Cystic hygroma- Occurs most commonly in association with Turner’s syndrome. Usually nuchal, but may rarely extend into the thorax.
· Cystic adenomatoid malformation- May be multicystic with evidence of space occupation, or an echogenic mass lesion. Hydrops may occur due to compromise of venous return to the heart. Usually regress during pregnancy. Polyhydramnios may occur.
· Hemangioma/lymphagioma- These are rare cystic masses that occupy the mediastinum. Remangiomas may have a solid component, depending upon the size of vessels involved.
· Intralobar sequestration- Cysts are occasionally seen within an intralobar sequestration, which may make differentiation from other cystic intrathoracic masses difficult.
· Neuroblastoma- These may be visualized as purely cystic mediastinal masses; however, a complex or solid appearance is not unknown.
· Dialted proximal blond esophageal pouch- This has been detected antenatally as a large, purely cystic posterior mediastinal mass.
· Mediastinal meningomyelocele/ menigocele- These appear cystic with variable thickness of its wall, which may be associated with vertebral defect; FH and PH may be present.
· Cystic dilatation of the bronchus- Massive cystic dilatation involving the left main bronchus has been detected antenatally by sonography.
· Enteric/ neuroenteric cysts- Usually unilocular, but multilocular posterior mediastinal cysts have been described. Diagnosis is suggested by the position of the cyst adjacent to the bowel and spine. They are often associated with vertebral abnormalities.
· Simple lung cyst- These appear as well defined cystic masses, unilocular, surrounded by normal lung.
Prominent pulmonary veins- These may resemble other cystic mediastinal lesions; however, with careful attention to detail, confusion should not arise
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