Purpose or Case Report: The case was a fetus in a 29-year-old mother (gravida 3, para 1). At 29 weeks of gestation, she was referred to our hospital due to abnormality of fetal heart sounds. On fetal MRI, the right pulmonary agenesis was suspected. A 3.5-kg baby girl was born at 41 weeks and 1 day of gestational ages by cesarean section with Apgar scores of 6 and 9 at 1 and 5 minutes respectively. Her respiratory status was stable under administration of 30% oxygen in an incubator.
Methods & Materials: To examine her pulmonary and cardiovascular system, contrast-enhanced CT was performed at 1 day old. The mediastinum was deviated to the right side, and almost occupied the entire right thoracic cavity. The significant small right lung was found at the base and posterior part of the right thoracic cavity. The right lung parenchyma was fused with the left lower lobe of the lung between the heart and esophagus. The very small pulmonary artery arose from the trunk of the pulmonary artery and reached the right hypoplastic lung parenchyma. The very small pulmonary vein which flowed to the left atrium from the right hypoplastic lung was also found. The bronchus which deviated to the right hypoplastic lung was indistinct.
Results: The pulmonary agenesis, aplasia and hypoplasia are defined as follows. 1) The pulmonary agenesis: complete absence of lung parenchyma, bronchus, and pulmonary vasculature. 2) The pulmonary aplasia: blind-ending rudimentary bronchus is present, without lung parenchyma or pulmonary vasculature. 3) The pulmonary hypoplasia: the bronchus and rudimentary lung are present; however, the airways, alveoli, and pulmonary vessels are decreased in size and number. In our case, right pulmonary agenesis was suspected on fetal MRI, but contrast-enhanced CT revealed very small right lung parenchyma found at the base of the right thoracic cavity afterbirth. Because this hypoplastic right lung had a very small pulmonary artery and vein, we considered that it was an extremely hypoplastic right lung. Moreover, this hypoplastic lung was fused with the left lower lobe of the lung. Horseshoe lung usually involves unilateral lung hypoplasia which is almost always on the right side. Therefore, we considered diagnosis of our case was not right lung agenesis but horseshoe lung with extremely hypoplastic right lung.
Conclusions: Our case suggests that horseshoe lung and pulmonary agenesis may be included in the spectrum of the same anomaly.