Right aortic arch and agenesia of left pulmonary artery

Clinical History

56 years old patient with long standing abnormalities of the left hemithorax including volume reduction, irregular pleural interface, pleural thickening, right aortic arch and atypical shape of the left pulmonary hilum

Imaging Findings

Clinical History : This is a 56-year-old white male with coronary heart disease and a history of a myocardial infarction two years ago. He underwent PTCA of the LCA and received a coronary stent several weeks after myocardial infarction. His medical history is further remarkable for a rejection from the army when he was drafted at age of 19 years. He was first rejected because of an „insufficient physical development“. He was redrafted one year later and was again rejected, this time because of an abnormal chest X-ray that led subsequently to further investigations. The patient has no pulmonary complaints and he has never smoked. He missed once school for several weeks because of a prolonged lower respiratory infection during his childhood, but he has never since suffered from recurrent or prolonged bronchitis. The physical exam is remarkable for decreased breath sounds on the left side. There is a systolic murmur over the right anterior chest. The chest appears normal on inspection. Pulmonary function testing reveals a mild restrictive defect (TLC 78% predicted), no obstruction and a normal diffusing capacity for CO. An ECG was normal and a recent echocardiography failed to demonstrate signs of pulmonary hypertension. Imaging procedures : Chest X ray and CT were performed to evaluate the anatomy of the mediastinum and lungs in preparation of a planned coronary bypass surgery. The actual chest X-ray showed an remarkable volume reduction of the left lung with consecutive mediastinal shift. An right aortic arch is seen. The pleura of the left lung is irregular and thickened. The right lung is of normal appearance. CT images (pulmonary artery angio-CT protocol, 4x1 mm, RI 1.25 mm, Increment 1 mm, 150 ml contrast media, 3 ml/sec, delay 30 sec) shows the absence of the left pulmonary artery. The pulmonary veins are hypoplastic compared to the contralateral side but both left pulmonary veins are present. The pleural fat plane in the left hemithorax is thickened . Multiple widened intercostal arteries are seen. The pleuro-pulmonary interface shows multiple wedge-shaped pleural abnormalities which extend into thin intrapulmonary septa. Viewing of the entire image stack on CT workstation revealed multiple intercostal arteries crossing the pleura at these locations and entering the lung parenchyma.

Discussion

Conventional X-ray of the thorax showed an volume reduction of the left hemithorax. Differential diagnosis of unilateral volume reduction included 1. congenital abnormalities of the pulmonary artery such as unilateral hypoplasia, aplasia, coarctation or atypical origin (ring sling etc.) 2. Swyer-James Syndrome 3. volume loss due to chronic pneumonia (less probable: no opacification) 4. volume loss doe to pleural changes such as fibrosis or mesothelioma (less probable: no effusion, probably long standing changes) 5. The CT findings showed clearly the absence of the left pulmonary artery. Many different congenital abnormalities with and without associated cardiac abnormalities may affect the pulmonary arteries. The typical radiologic features of unilateral agenesis of the pulmonary artery include a small hemithorax, ipsilateral displacement of the mediastinum, absence of the pulmonary artery and reticular abnormalities along the pleura due to systemic collateral blood supply to the affected lung. Absence of the pulmonary artery is an result of misdevelopment of the proximal portions of the right or the left sixth arch of embryonal circulation and can, consequently, be associated with congenital heart disease, especially tetralogy of Fallot. In the present case, however, no congenital heart disease is present.

Differential Diagnosis List

Final Diagnosis

right aortic arch with agenesia of left pulmonary artery

URL:	https://eurorad.org/case/682
DOI:	10.1594/EURORAD/CASE.682
ISSN:	1563-4086