Teaching Case

Dyspnea and one episode of blood-tinged sputum the night before. The clinical course of this patient had been complicated by slight impaired exercise tolerance since childhood. Physical examination revealed no abnormalities.

A 22-year-old female was admitted to the hospital with dyspnea and an episode of blood-tinged sputum the night before. The clinical course of this patient had been complicated by slight impaired exercise tolerance since childhood. Physical examination revealed no abnormalities. Plain radiograph, CT scan and DSA were performed. Angiographic findings were consistent with unilateral absence of the right pulmonary artery (UPAA) and underdevelopment of the right lung.

Congenital absence of a pulmonary artery is a rare anomaly. It is frequently associated with other cardiovascular anomalies, such as tetralogy of Fallot, right aortic arch, septal defects and patent ductus arteriosus. There is no predilection for the right or left side, although the condition is somewhat more common on the right. Although the side of the agenesis is not predictive for the presence of associated cardiac pathology, right-sided agenesis is less frequently associated with cardiac abnormalities. Physical examination is mostly unremarkable with exception for decreased breath sounds on the involved side. An isolated UPAA shows a characteristic pattern of chest roentgenography findings, including cardiac and mediastinal displacement, absence of the pulmonary artery shadow, smaller hemithorax, elevation of the diaphragm and paucity of the vascular markings, all on the involved side. On the opposite side, there may be hyperinflation and herniation of the lung across the midline. Ventilation-perfusion scan is an important diagnostic tool but DSA is definite in establishing the diagnosis of UPAA. The affected lung is supplied by systemic collaterals (hypertrophic bronchial arteries, intercostal and other transpleural collaterals), but pulmonary venous return is normal in most cases. The clinical course is mostly benign and when symptoms occur, they are often related to recurrent respiratory tract infections with bronchiectasis. Since symptoms are subtle and physical examination mostly normal, clinical diagnosis of UPAA of the adult is difficult. It should always be considered in the differential diagnosis of a unilateral hyperlucent lung.