Pulmonary hypertension may primarily affect either the arterial (precapillary) or the venous (postcapillary) pulmonary circulation. Pulmonary arterial hypertension may be idiopathic or arise in association with chronic pulmonary thromboembolism; pulmonary embolism caused by tumor cells, parasitic material, or foreign material; parenchymal lung disease; liver disease; vasculitis; human immunodeficiency virus infection; or a left-to-right cardiac shunt. Its histologic characteristics include vascular changes-medial hypertrophy, intimal cellular proliferation, intraluminal thrombosis, and the development of plexiform lesions-that manifest primarily in the muscular pulmonary arteries. Features of pulmonary arterial hypertension that may be seen at computed tomography (CT) are central pulmonary artery dilatation, abrupt narrowing or tapering of peripheral pulmonary vessels, right ventricular hypertrophy, right ventricular and atrial enlargement, dilated bronchial arteries, and a mosaic pattern of attenuation due to variable lung perfusion. Pulmonary venous hypertension may result from pulmonary veno-occlusive disease, pulmonary venous compression by extrinsic lesions (eg, mediastinal fibrosis), left-sided cardiac disease, or pulmonary vein stenosis. Its histologic hallmarks include venous intimal cellular proliferation, medial hypertrophy, and thickening of the internal elastic lamina; capillary congestion and proliferation; interlobular septal thickening; lymphatic dilatation; and, sometimes, venous infarction and vascular changes characteristic of pulmonary arterial hypertension. CT scans in patients with pulmonary venous hypertension show pulmonary interstitial and alveolar edema with signs of pulmonary arterial hypertension. High-resolution CT with standard axial and angiographic acquisitions is useful for identifying underlying disorders and differentiating among the various causes of secondary pulmonary hypertension.
© RSNA, 2010.