Horseshoe lung associated with rare bilateral variant of scimitar syndrome: demonstration by 64-slice MDCT angiography

Adult congenital horseshoe lung with bilateral pulmonary sequestration: A case report

Horseshoe lung (HL) is an infrequent congenital lung anomaly. Its main feature is that the lower lungs on both sides extend behind the pericardium and fuse across the midline, usually accompanied by pulmonary dysplasia. It is reported that 80% of HL is relevant to the abnormal return of some pulmonary veins from the right lung to the inferior vena cava or right atrium (scimitar syndrome). Most patients are within 5 years old, most commonly within 1 year old, but HL may also have no apparent clinical symptoms or mild symptoms. This case is a 36-years-old adult female who developed left chest pain more than a month ago and continued to worsen for 10 days. The patient also had repeated pulmonary infection with cough and expectoration.

Posterior Lung Herniation in Pulmonary Agenesis and Aplasia: Chest Radiograph and Cross-Sectional Imaging Correlation

Objective

To describe the anatomic locations and imaging features of posterior lung herniation in unilateral pulmonary agenesis and aplasia, focusing on radiograph-CT/MRI correlation.

Materials and Methods

A total of 10 patients (seven with pulmonary agenesis and three with pulmonary aplasia, male: female = 1:9, mean age 7.3 years, age range from 1 month to 20 years) were included. Chest radiographs (n = 9), CT (n = 9), and MRI (n = 1) were reviewed to assess the type of lung underdevelopment, presence of anterior and posterior lung herniation, bronchus origin, supplying artery, and draining vein of the herniated lung.

Results

Pulmonary agenesis/aplasia more commonly affected the left lung (n = 7) than the right lung (n = 3). Anterior lung herniation was observed in nine of the 10 patients. Posterior lung herniation was observed in seven patients with left pulmonary agenesis/aplasia. Two patients showed posterior lung herniation crossing the midline but not beyond the aorta, and five patients showed the posteriorly herniated right lower lobe crossing the midline to extend into the left hemithorax farther beyond the descending thoracic aorta through the space between the esophagus and the aorta. This anatomical configuration resulted in a characteristic radiographic finding of a radiolucent area with a convex lateral border and a vertical medial border in the left lower lung zone, revealing a tongue-like projection on CT and MRI.

Conclusion

Posterior lung herniation occurs in unilateral left lung agenesis/aplasia. Approximately 70% of the cases of posterior lung herniation reveal a unique radiolucent tongue-like projection in the left lower lung zone on imaging studies, which is caused by the extension of the posteriorly herniated right lung farther beyond the descending aorta.

Horseshoe lung associated with scimitar syndrome

Horseshoe lung is a rare congenital anomaly and mostly accompanied by scimitar syndrome. Most aspects of this complex anomaly can be demonstrated via multidetector CT (MDCT). We present two baby girls who had horseshoe lung associated with right lung hypoplasia and scimitar vein. The chest roentgenograms showed displacement of the heart and mediastinum to the right with smaller right lung. Echocardiography revealed dextroposition, secundum atrial septal defect and bilateral slight peripheral pulmonary stenosis in the first case and dextroposition, severe pulmonary hypertension, secundum atrial septal defect and tricuspid regurgitation in the other one. On thoracic MDCT, the right lung and pulmonary artery were hypoplastic with cardiomediastinal shift to the right. There was an abnormal right pulmonary vein draining into the inferior vena cava on the lower zone of the right lung (scimitar vein). The posterobasal portions of the both lungs were fused through a midline isthmus behind the heart.

Scimitar syndrome: the curved Turkish sabre

Scimitar syndrome is a rare association of congenital cardiopulmonary anomalies characterized by an anomalous pulmonary vein (scimitar vein) that drains into the inferior vena cava, a hypogenetic right lung, and dextroposition of the heart. It has been reported in 3% to 6% of patients with partial anomalous pulmonary venous connection. Patients are either diagnosed early with severe symptoms (infantile type) or late with minimal symptoms (childhood/adult type). In this chapter we reviewed the history, pathophysiology, presentation, diagnosis, and treatment methods of Scimitar syndrome in the current era.

Horseshoe lung associated with left-lung hypoplasia, left pulmonary artery sling and bilateral agenesis of upper lobe bronchi

Horseshoe lung, a rare congenital anomaly, is almost always associated with unilateral (usually right-sided) lung hypoplasia, and, in most cases, in conjunction with the scimitar syndrome. We present an 8-month-old boy with horseshoe lung associated with left-lung hypoplasia, left pulmonary artery sling and bilateral agenesis of the upper lobe bronchi, diagnosed by multidetector CT (MDCT) imaging. The study also revealed an anomalous origin of the left vertebral artery as the last branch of the aortic arch, distal to the left subclavian artery, and an anomalous origin of the left common carotid artery from the brachiocephalic trunk. A hemivertebral anomaly of the seventh cervical vertebra was incidentally detected. MDCT with high-quality multiplanar and three-dimensional reconstructions is a noninvasive and rapid technique for detecting the complex combination of vascular, tracheobronchial and parenchymal anomalies, and any potential bone anomalies, in one imaging study.