Fetal Solid Lung Masses
· Cystic adenomatoid malformation type III- The cysts are usually so small that they cannot be seen. The multiple interfaces give rise to the impression of an echogenic solid lung mass.
· 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.
· Lobar sequestration- Lobar sequestration presents as an echogenic lung mass. Cysts can be present in intralobar sequestration, which makes differentiation form type I and II cystic adenomatoid lung difficult.
· Extralobar sequestration- Less common than intralobar sequestration. Usually left sided, lying near the diaphragm where it may be confused with a diaphragmatic hernia. Extralobar sequestrations have a good prognosis, unless associated with hydrops and pleural effusions.
· Brochial attresia- US features include enlarged echogenic lung, ascites, hydrops, and abnormalities of the trachea and esophagus.
· Congenital lobar emphysema- This must be differentiated from cystic adenomatoid malformation type III. FH is less likely to occur in congenital lobar emphysema.
· Chest wall hamartoma- This may be confused with a lung mass. The sonographic features are those of a highly echogenic intrathoracic mass. The mass may be partly calcified and may have densely echogenic areas. The intrathoracic component may be identical to a calcified thoracic neuroblastoma.
· Ectopic kidney- Intrathoracic kidney is a rare anomaly, which, if present, usually occurs on the left. The reniform shape, and the absence of the kidney in its normal position, gives away the diagnosis.
· Rhabdomyomas- Rhabdomyomas may be cardiac or extracardiac. The two varieties are unrelated; the cardiac type is most probably hamartomas. Both types present as solid tumors and are exceedingly rare.
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