Diseases of the pulmonary arteries: imaging appearances and pearls

A wide spectrum of pathology, both congenital and acquired, can affect the pulmonary arteries. While some of these are commonly seen in everyday clinical practice, some are rare. These entities may be discovered incidentally at imaging for other reasons in an asymptomatic patient, however patients may go on to develop symptoms over the course of their lifetime. Although an enlarged pulmonary artery can be visualized on chest X-ray (CXR), for the most part, CXR is insensitive for detecting abnormalities of the pulmonary arteries. Contrast-enhanced chest CT (CECT) is a better test to evaluate the pulmonary arteries as it is readily available, quick to perform, able to provide multiplanar reformatted images, and noninvasive. CECT is not only able to assess the lumen and wall of the pulmonary artery, but also provides a detailed evaluation of the entire thorax, including the heart, mediastinal structures, and lungs, often times picking up associated findings, and is the mainstay for evaluating disorders of the pulmonary vasculature. MRI allows for detailed evaluation of the vessel wall which can be especially helpful in cases where malignancy or vasculitis are suspected, and is also able to provide useful physiologic data such as quantification of flow. It is important for the radiologist to be aware of the many conditions which affect the pulmonary arteries, as some may require urgent treatment. This article will review normal pulmonary artery anatomy and physiology, as well as the various imaging findings of pulmonary vascular pathologies.