Pictorial review of the pulmonary vasculature: from arteries to veins
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Pathology of the pulmonary vasculature involves an impressive array of both congenital and acquired conditions. While some of these disorders are benign, disruption of the pulmonary vasculature is often incompatible with life, making these conditions critical to identify on imaging. Many reviews of pulmonary vascular pathology approach the pulmonary arteries, pulmonary veins and bronchial arteries as individual topics. The goal of this review is to provide an integrated overview of the high-yield features of all major disorders of the pulmonary vasculature. This approach provides a more cohesive and comprehensive conceptualisation of respiratory pathology. In this review, we present both the salient clinical and imaging features of congenital and acquired disorders of the pulmonary vasculature, to assist the radiologist in identifying pathology and forming a robust differential diagnosis tailored to the presenting patient.
• Abnormalities of the pulmonary vasculature are both congenital and acquired.
• Pathology of a single pulmonary vascular territory often affects the entire pulmonary vasculature.
• Anomalous pulmonary venous flow is named as a function of its location and severity.
• Bronchial arteries often undergo dilatation secondary to cardio-respiratory pathology.
KeywordsPulmonary artery Pulmonary veins Bronchial arteries Pulmonary medicine Diagnostic imaging
Overview of imaging of the pulmonary vasculature
Multiple imaging modalities are available to assist in the evaluation of the pulmonary vasculature including chest radiography, ultrasonography, magnetic resonance imaging (MRI) and computed tomography (CT). As a general rule, a chest radiograph is limited in its assessment potential for these conditions [1, 2]. In infants and children with suspected congenital anomalies, ultrasound may be the first line choice with MRI as a useful follow-up study to clarify anatomy and follow conditions as it does not expose the patient to ionising radiation . CT remains the “gold standard” for evaluating most vascular pathology due to its ability to clearly elucidate anatomical detail and is often the preferred imaging modality to get a detailed look at complex pulmonary vascular anatomy, at least on initial assessment.
Although pulmonary arteries and veins are commonly imaged without the assistance of electrocardiographically (ECG) gated imaging (MR or CT), in certain circumstances cardiac gating can improve the visualisation of the central pulmonary vasculature. For example, ECG-gating assists in the detailed imaging of the pulmonary vein ostia that is required in the setting of pulmonary vein mapping for pre-ablation imaging and in pre-procedure pulmonic valve replacement planning . Imaging of the pulmonary vasculature is improved using a dedicated angiographic technique in which the timing of the contrast bolus is targeted to the vessel or structure of interest. This is commonly achieved using either a test bolus to determine peak enhancement or a bolus-tracking method to determine when the level of enhancement begins to increase in a structure of interest. For imaging of pulmonary arteries, the main pulmonary artery will be the target structure and for imaging of the pulmonary veins, the left atrium will be the target structure. A contrast flow rate of at least 3 cc/s is recommended to reduce the risk of insufficient enhancement of the target structure. The volume of contrast and duration of scan time needed for imaging will depend on the type of scanner used (e.g. dual source or 16/64/256-slice multidetector CT), with faster scanners decreasing scan time and amount of contrast volume needed .
Imaging of the bronchial arteries is often difficult due to their small size and tortuous course. Techniques to improve enhancement of these vessels includes contrast administration targeted to the arterial/aortic phase of imaging to optimise enhancement and three-dimensional volumetric or multiplanar imaging reconstructions to optimise the plane of imaging .
Pulmonary artery abnormalities
Congenital disorders of the pulmonary artery
Pulmonary artery atresia
Pulmonary artery sling
Idiopathic dilatation of the pulmonary trunk
Acquired disorders of the pulmonary artery
Causes of pulmonary hypertension
Type of pulmonary hypertension
1. Pulmonary arterial hypertension
This category is broken down further into several subcategories. These categories include: idiopathic, heritable and drug/toxin induced. There is also a category for pulmonary arterial hypertension secondary to certain diseases, including congenital heart disease, connective tissue diseases, HIV infection, portal hypertension and schistosomiasis. Group 1′ includes pulmonary veno-occlusive disease (PVOD) and/or pulmonary capillary haemangiomatosis. Group 1″ is persistent pulmonary hypertension of the newborn.
2. Pulmonary hypertension secondary to left heart disease
This category may be caused due to left-heart disease of the valves, systolic dysfunction or diastolic dysfunction. The Nice classification added congenital/acquired left heart inflow/outflow tract obstruction along with congenital cardiomyopathies to this category.
3. Pulmonary hypertension with lung disease/hypoxaemia
This category may be caused by COPD, interstitial lung diseases, pulmonary diseases with a mixed restrictive and obstructive pattern, sleep-disordered breathing, alveolar hypoventilation disorders, chronic exposure to high altitude and developmental lung diseases.
4. Chronic thromboembolic pulmonary hypertension
This category arises in patients who have had chronic thromboembolic disease resulting in reorganisation of the pulmonary vasculature.
5. Pulmonary hypertension with unclear multifactorial mechanism
This is a broad category that includes pulmonary hypertension secondary to haematological disorders (including chronic haemolytic anaemia), systemic disorders (like sarcoidosis and lymphangioleiomyomatosis), metabolic disorders (like glycogen storage diseases or thyroid disorders) and other causes (including chronic renal failure and segmental pulmonary hypertension).
Pulmonary artery aneurysm/pseudoaneurysm
Pulmonary artery narrowing/obstruction
Pulmonary vein abnormalities
Congenital variations in number
Anomalous pulmonary venous return
Pulmonary vein varix
Pulmonary vein congenital atresia/stenosis
Failure of the pulmonary vein to properly develop may result in atresia or stenosis. Patients will classically present with recurrent pneumonia and/or haemoptysis in the first few years of life, and there is an association with other congenital cardiac anomalies . CT imaging may show ipsilateral mediastinal deviation towards the atretic pulmonary vein, a small ipsilateral hemithorax and a small ipsilateral pulmonary artery .
Pulmonary vein stenosis/obstruction
Pulmonary vein collateral pathways
Pulmonary venous hypertension
Pulmonary venous hypertension (defined as a pressure of 15 mmHg or higher) occurs most often in the background of left ventricular failure or other cardiac causes. A rare idiopathic cause of pulmonary venous hypertension is known as pulmonary veno-occlusive disease, which develops secondary to the occlusion or constriction of the pulmonary veins and venules, with the majority of patients affected presenting under the age of 50 years old [2, 38]. Patients with pulmonary venous hypertension show evidence of fluid overload on imaging, including pulmonary oedema and pleural effusions, mosaic attenuation of the pulmonary parenchyma and enlargement of the central pulmonary arteries .
Pulmonary vein calcifications
Pulmonary vein calcifications are typically associated with mitral valve disease and chronic renal failure; however, they may also be seen in patients with atrial fibrillation [2, 39]. In addition to pulmonary vein calcifications, imaging often shows a dilated left atrium, which may also be calcified, described as a “mould-like” pattern .
Other pulmonary vascular abnormalities
Pulmonary arteriovenous malformations
Bronchial artery abnormalities
Dilated bronchial arteries (> 2 mm) are often a sign of serious pathology and should prompt immediate investigation for an underlying cause (Fig. 20) . Several causes of bronchial artery dilation have been discussed in the previous sections, including congenital disorders of the heart and pulmonary artery, pulmonary artery obstruction and inflammatory conditions of the lungs . Of note, patients with idiopathic pulmonary hypertension do not typically have dilatation of the bronchial vasculature, providing a helpful tool in differential diagnosis .
In this pictorial review, we have presented a broad overview of pathology involving the pulmonary arteries, pulmonary veins and the bronchial arteries. Knowledge of these conditions, as well as normal anatomy of the pulmonary vasculature, is the cornerstone for building a differential diagnosis tailored to a patient’s clinical presentation and imaging features. This is especially important as many of these conditions have significant morbidity and mortality, underscoring the importance of the material presented.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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