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Horseshoe lung (HL) is a rare congenital pulmonary deformity in which the caudal and basal segments of the left and right lungs are joined together behind the pericardium at the height of cardiac apex. The feature of horseshoe lung was first described by Spencer in 1962. Horseshoe lung is often associated with other malformations such as scimitar syndrome, unilateral lung hypoplasia, congenital cystic adenomatoid malformation (CCAM) and esophagobronchial fistula.
We report a case of a fetus with HL without other intracardiac and extracardiac malformation, suspected prenatally on ultrasound image and confirmed with fetal MRI.
A 32-year-old woman, with no family history of congenital defects, were recommended to our department at 24 weeks and 5 days gestation, because of an abnormal aortic morphology. A fetal echocardiographic evaluation in our department showed the aortic arch and thoracic aortic enlarged with abnormal direction. There was no evidence of intracardiac and great vessel anatomic abnormalities, bone dysplasia, or other extracardiac deformities.
Fetal MRI was therefore performed to assess the cause of aortic translocation, and showed the basement of the lungs fused in front of the spine and thoracic aorta. The fused lungs across the mediastinum confirmed the diagnosis of fetal horseshoe lung. Meanwhile the fetal MRI also demonstrated that without pulmonary hypoplasia, esophageal atresia or great vessel deformities.
The definite diagnosis of horseshoe lung rely on imaging technology. CT is the best postnatal imaging modality for assessment of HL anatomy, evaluation of the lung anomalies development. The pulmonary artery and vein can be clearly identified by contrast-enhanced CT. Prenatal MRI and sonography can confirm the diagnosis of HL, clearly demonstrate the communication between the lungs. When the fetal echocardiology demonstrate the displacement of the heart and the abnormal position of the great vessels, we should take further fetal MRI to confirm the presence of horseshoe lung. The prenatal diagnosis should make definite diagnosis about HL, also should make sure whether there is intracardiac deformities.