Findings: The CT scan demonstrates a right upper lobe vascular structure whose insertion is difficult to distinguish. On angiography, an anomalous connection of the right upper lobe pulmonary vein is noted with the superior vena cava. No evidence of a pulmonary embolus was identified.
Diagnosis: Partial anomalous pulmonary venous connection.
Discussion: Partial anomalous pulmonary venous connection (PAPVC) is present when one or more, but not all, of the pulmonary veins connect to a systemic vein, the right atrium, or the coronary sinus. The veins of the right lung have two to ten times the number of anomalous connections as those from the left lung. When an anomalous vein exists, it usually connects to the nearest adjacent systemic vein. The left lung veins connect to the left innominate vein, the coronary sinus, the hemiazygous vein, or to an anomalous vertical vein that drains into the innominate vein. In the right lung, the right superior pulmonary vein may connect to the right superior vena cava or azygous vein. The right inferior vein may connect with either the inferior or superior vena cava, or hepatic vein, or the azygous vein. The right pulmonary veins may also connect directly to the right atrium. Less common variations include absence of the coronary sinus with pulmonary veins from either side connecting to multiple systemic sites or to the left atrium. Rarely, an anomalous pulmonary vein will connect to the portal vein. Many variations exist in the number, size, and connections of the four pulmonary veins. If an atrial septal defect is present, about 10% of patients will have a pulmonary venous abnormality. The chest radiograph is usually normal because the pulmonary-to-systemic flow ratio is generally less than two to one.
When an entire lung is drained by an anomalous connection, the main pulmonary arteries are slightly enlarged. One type of anomalous pulmonary vein is easily identified on the chest film. The"scimitar sign" consists of a linear opacity, usually but not always at the base of the right lung, which widens as it courses inferiorly and ends in the inferior vena cava.
The hypogenetic lung syndrome is a rare congenital anomaly that consists of anomalous pulmonary venous drainage to the inferior vena cava, hypoplastic or aplastic pulmonary artery segments, and hypoplastic or absent bronchi. The hypoplasia of the right lung secondarily may rotate the heart toward the right hemithorax and cause a mild dextrocardia.
Pulmonary venous anomalies may be identified with cross-sectional imaging and obviate the need for further studies. Because of the relatively high prevalence of PAPVC, a number of cases will be discovered incidentally during CT scans for other reasons. CT will demonstrate the course and termination of the anomalous vein, the bronchial distribution, abnormal lobation, and mediastinal shift and confirm the distinction from other venous structures, such as a left superior vena cava, pulmonary varices, and pulmonary arteriovenous fistulas. Since the majority of patients with PAPVC are asymptomatic, further evaluation after positive identification with CT is usually unwarranted. Complications of PAPVC result from pulmonary infection, atrial septal defect or dilation of the right atrial septal defect, or dilation of the right atrium and ventricle. Other imaging modalities may be required in these circumstances.
Pulmonary angiography remains the standard examination for locating all the pulmonary veins. Selective injection into the right and left pulmonary arteries will visualize all pulmonary veins during a prolonged filming sequence. Alternative methods of locating pulmonary veins at catheterization include exploring the right atrium and adjacent systemic veins and documenting the anomaly by the entrance of the catheter into the vein or by a small hand injection of contrast material.
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