대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Left isomerism

Radiologic Findings

Chest PA radiograph shows the large and elevated right hilum with symmetrical hyparterial bronchi. We can’t see the normal right pulmonary arterial opacity anterior to main stem bronchi and the line representing posterior wall of the bronchus intermedius on lateral radiograph. Chest CT scans show the course and relationship of the right pulmonary artery and right central airway analogous to those of the left lung.

Brief Review

Thoracic isomerism, the condition in which the anatomy of the two lungs is symmetrical, is usually a component of situs ambiguis, in which asymmetric structure throughout the body tend to be symmetrical. Although it may be an isolated finding, it is frequently associated with a variety of cardiac, splenic, and other anomalies.

Symmetrical hyparterial bronchi ("bilateral left lung") have been described most frequently in the polysplenia syndrome, usually associated with significant cardiovascular anomalies including atrial and ventricular septal defects, anomalous pulmonary venous return, azygos or hemiazygos continuation of the inferior vena cava. Such patients may also demonstrate abdominal heterotaxia, malrotation of the bowel, horizontal liver, and absent gallbladder. Because of the strong association with serious congenital heart disease, thoracic isomerism is rare in adults.
Indirect determination of atrial situs can be inferred from the disposition of the tracheobronchial tree imaged from either the plain chest radiograph or high kilovoltage filtered films. Bilaterally long and left-appearing bronchi are consistent with left atrial isomerism. Unequivocally, bronchial anatomy is more consistently predictive of atrial situs than the radiographic appearance of visceral situs, although even bronchial anatomy may not correlate with atrial anatomy. The lateral chest radiograph is also helpful in defining the status of the bronchial branching pattern. Pulmonary arteries cast a shadow behind the bronchial shadows in left isomerism.

References

1. Landay MJ, Shaw C, Bordlee RP. Bilateral left lungs: Unusual variation of hilar anatomy. AJR 1982;138:1162-1164
2. Freedom RM et al. Congenital heart disease: textbook of angiography. Futura Publishing Company, 1997, 104-106, 1261-1263.

Keywords

Multiple organs, Congenital,