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ECR 2013 / C-2107
Pulmonary vascular patterns in chest radiograph
This poster was previously presented in Spanish at the 2012 Congreso Nacional SERAM (Granada)
Congress: ECR 2013
Poster No.: C-2107
Type: Educational Exhibit
Keywords: Thorax, Pulmonary vessels, , Diagnostic procedure
Authors: P. Rodriguez Carnero, A. Cárdenas del Carre, A. Bustos García de Castro; Madrid/ES
DOI:10.1594/ecr2013/C-2107

Imaging findings OR Procedure details

Pulmonary vascular patterns:


On the following paragraphs we will discuss the main pulmonary vascular patterns, beginning with normality, which is crucial to learn and understand in order to be able to appropriately identify pathological findings.  Fig. 2

 

Table 1
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

1-Normal vascular pattern


Pulmonary vascularity follows a tree-shaped distribution from the hila, being the vessels wider on the central areas and narrower on the periphery. Pulmonary vessels should be seen in a range of 1-2 cm proximal to the pleura. Vessels are normally seen as tubular structures of water-density on chest radiographs.

 

Pulmonary vascularity should be studied globally, checking that its distribution follows a normal pattern and that its morphology is acceptable. It is important to take into consideration that pulmonary vascular appearance and morphology might show a great variability among normal individuals.

 

We must also remember that both hila must be symmetric, and that most of the times the right hilum is lower or lies at the same level as the left hilum.

 

Due to gravity, the vessels of the lung bases usually are larger than the ones of the upper lobes on a chest radiograph of normal patients.

 

 

Fig. 2: Normal pulmonar vascularity. A. PA Chest radiograph of a normal patient. B. Diagram of normal lung vascularity. Pulmonary vascularity follows a centrifugal and symmetric distribution from both hila. The main pulmonary artery (AP) is not identified because it is superimposed to other anatomical structures of the anterior mediastinum. Actually, we can only recognize its left lateral utmost (underlined in orange). Left hilum is higher than the right one and the vessels of the pulmonary bases are larger than the ones on the upper lobes.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Fig. 3: Normal pulmonary vasculature. Coronal Maximum intensity projection reconstruction of a contrast-enhanced thoracic CT. Notice that the vessels of the lung bases are wider than the ones of the upper lobes.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Fig. 4: Normal pulmonary vasculature. Chest radiograph, lateral projection. We can identify the proximal segment of the main pulmonary artery (orange dashed line) as well as the left (HI) and right (DH) hila (red dashed line).
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

If we pay attention we will notice that each bronchus goes along with a vessel (which generally corresponds to an artery).  Fig. 5

 

 

Fig. 5: Twins sign. PA Chest radiograph of the same patient as shown in fig.2, with no abnormalities. Notice that, in the bigger extended image, the bronchi and the vessel have the same width (twins sign).
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

2-Vascular redistribution pattern


Consists in an inversion of the normal relationship between the upper and lower vessels: the vessels of the upper lobes are wider or equal in size to the ones of the lung bases.

 

The vascular redistribution pattern is usually due to a pulmonary venous congestion, which in turn is caused by heart failure, mostly of left cavities. This situation increases pulmonary capillary venous pressures, causing pulmonary vascular stasis, which is more self-evident on the vessels of the upper lobes. This phenomenon of vascular redistribution is patent on chest radiographs when the venous pulmonary pressures are between 15 and 20 mmHg (pressures measured in the left auricle).  Fig. 6

 

 

Fig. 6: Vascular Redistribution pattern. PA chest radiograph of a patient with mitral stenosis. Diagram of the redistribution pattern. Pulmonary vessels of the upper lobes are wider than the ones of the lower lobes. Global cardiomegaly, more patent in left cavities.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Whenever we identify a vascular redistribution pattern we must run a differential diagnosis of entities which might cause pulmonary venous hypertension.  Table 2

 

 

Table 2
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

The patient shown on Fig. 7, with a treated mitral regurgitation, is another example of a pulmonary vascular redistribution pattern.

 

 

Fig. 7: Vascular redistribution pattern. PA-Chest radiograph of a patient with mitral insufficiency treated with previous surgery. Notice that the vessels of the upper lobes are similar or wider than the ones of the lower lobes. Not only post-valve exchange sternotomy is seen, but also global cardiomegaly secondary to valvulopathy. Also notice a linear calcification in the left auricle wall (arrowhead).
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Heart failure is the most frequent aetiology of vascular redistribution. However, it is important to notice that in cases of severe interstitial or even pulmonary oedema (pressures measured in the left auricle being higher than 25 mmHg), it might be difficult to identify this pattern.  Fig. 8.

 

 

Fig. 8: AP chest radiograph of a patient with heart failure and pulmonary ooedema. Heart failure is the most frequent aaetiology of redistribution pattern. However, it is important to notice that in cases of severe pulmonary ooedema this pattern might not be seen because the alveolar and interstitial ooedema hides the normal contour of the vessels.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

3-Pulmonary arterial hypertension pattern


Both hila are increased in size, generally in a symmetrical manner, at the expense of the right and left pulmonary arteries and the pulmonary trunk. Most of the time this phenomenon is accompanied by a decrease in the width of peripheral pulmonary vessels.  Fig. 9 and Fig. 10.

 

 

Fig. 9: Pulmonary arterial hypertension pattern. A. PA chest radiograph of a patient with COPD and pulmonary hypertension. B. Diagram of pulmonary hypertension. Notice widening of the main pulmonary artery (black arrowheads on the x-ray and orange dot in the diagram) and increase of the pulmonary hila, more noticeable on the right lung (white arrowheads). Peripheral lung vasculature is diminished, both in distribution and size.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Fig. 10: Pulmonary arterial hypertension pattern. A. Lateral projection of a chest radiograph of the same patient as shown on figure 8. There is an increase of the vascular structures of the hila (left hilum: white arrowheads; right helium: black arrowheads). B. Contrast enhanced chest CT of the same patient. There is an increase in the width of main pulmonary arteries, right and left. Whenever the pulmonary trunk is wider than 3 cm it is considered a pathologic finding.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

A useful measurement to remember when reading a PA chest radiograph is the diameter of the interlobar artery: its diameter should not be higher than 16-17 mm. If it is higher, we may consider it dilated. This measurement is useful to identify an increase of the pulmonary arteries.  Fig. 11.

 

 

Fig. 11: Pulmonary hypertension pattern. PA chest radiograph of a patient with known COPD and aortic stenosis. Notice widening of the pulmonary hila, mostly of its vessels. There is also expansion of the main pulmonary artery (also known as pulmonary trunk, marked in orange) and amputation of peripheral vessels. The width of the interlobar right artery is considered normal when its diameter runs between 16 and 17 mm. Aortic stenosis causes cardiomegaly, mostly of left chambers.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

This pulmonary vascular pattern is related to the presence of pulmonary arterial hypertension. The pathophysiology is explained by an increase of the pulmonary blood flow resistance, which causes an increase of the pulmonary arterial pressure (over 25 mmHg resting), and hence this phenomenon will induce right heart failure and a decrease in the cardiac output.

 

These phenomena explain the increase in the size of the central pulmonary arteries, accompanied by a decrease in the width and number of peripheral arteries by means of reactive vasoconstriction and/or dysfunction of these vessels (which is believed to be due to hypoxemia and alveolar hypoxia).

 

Likewise, we can find radiological findings which might suggest right heart failure (cor pulmonale).

 

Table 3 shows the main etiologies of pulmonary arterial hypertension pattern.

 

 

Table 3
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

4- Vascular overcirculation pattern


It shows an increase in the pulmonary blood flow, which subsequently causes dilation of both central and peripheral pulmonary vessels, in a symmetric and bilateral distribution, frequently accompanied by cardiomegaly, mostly of right cavities. Fig. 12.

 

 

Fig. 12: Pulmonary overcirculation pattern. A. PA chest radiograph of a patient with atrial septal defect. B. Diagram of pulmonary overcirculation pattern. Notice an increase of the pulmonary vasculature, both in the hila and in the periphery, which is symmetric and bilateral. Pulmonary trunk size is increased (marked in orange). There is also cardiomegaly and an azygos lobe.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

There are different entities which might cause vascular overcirculation pattern, which are shown on  Table 4.

 

 

Table 4
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

The patient on Fig. 12 suffered from an atrial septal defect. He underwent surgery, improving later the radiological appearance of vascular overcirculation pattern. In the Fig. 13 we can see the chest radiographs before and after surgical treatment.

 

 

Fig. 13: Pulmonary overcirculation pattern. PA chest radiograph of the same patient as shown in Fig.12. A. Pulmonary overcirculation pattern before surgery of the atrial septal defect. B. Overcirculation improvement after treatment with an Amplatzer septal occluder device.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

5-Diminished pulmonary blood flow pattern


The lung showing diminished blood flow pattern has a markedly reduced blood flow in the pulmonary circulation. Vascularity of both lung fields appears diminished in width and in the number of vessels, both in the hila and in the periphery.  Fig. 14.

 

 

Fig. 14: Diminished Pulmonary Blood Flow pattern. A. PA chest radiograph of a patient with a previously diagnosed Swyer-James-McLedod Syndrome. B. Diagram of Diminished Pulmonary Blood Flow in left circulation, with normal right circulation. Left lung is diminished in size and volume. Notice a generalized increased radiolucency in this side, caused by a decrease in both central and peripheral circulation, as well as alveolar hyperinflation. Right lung has a normal vascular pattern. We can also appreciate post-surgical changes of Bentall procedure, performed after an ascending aortic aneurysm was diagnosed. A heart pacemaker is also shown.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

The main aetiologies of diminished pulmonary blood flow pattern are summarized on 

Table 5
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

Sometimes the pathologic pulmonary vascular patterns are localized in a single lung, or even a single lobe or segment. The patient shown on Fig. 14, who showed a diminished left pulmonary blood flow pattern, was diagnosed of a homolateral Swyer-James-McLeod syndrome, as a consequence of a bronchiolitis obliterans suffered during childhood. On Fig. 15 we can see the main findings in the CT of this patient.

 

 

Fig. 15: Diminished Pulmonary Blood Flow pattern. Patient with Swyer-James-MacLeod syndrome on the left lung. A. PA Chest radiograph of the same patient as shown in figure 15. B. Maximum-Intensity-Projection reconstruction of a contrast-enhanced chest CT (lung window) of the same patient. Notice diminished blood flow on the left lung and an aneurysm of the ascending aorta. C. Contrast-enhanced CT of the same patient. Normal right pulmonary artery (D). Aneurysm of the ascending aorta. D: Contrast-enhanced CT of the same patient. Diminished width of the left pulmonary artery.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

6- Vascular “vicarious” pattern


This entity consists of the identification of bronchial arterial circulation on a conventional chest radiograph, which should not be seen in normal individuals.

 

Whenever the bronchial arteries are seen in the lung fields, they usually resemble an anarchic and disrupted net, which is certainly different to the normal tree-shaped distribution of pulmonary vessels. Fig. 16.

 

 

Fig. 16: Vicarious pattern. A and B. Detail of a PA radiograph of a patient with pulmonary trunk agenesis. There is near-complete absence of the right pulmonary helium and the presence of a reticular pulmonary vasculature, which resembles a disrupted net, ie. bronchial circulation. C and D. Details of a PA radiograph of another patient with normal pulmonary vasculature. Notice a tree-shaped distribution of the pulmonary vessels and a normal appearance of the right hilum.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

The aetiologies of the “vicarious” pattern are all the entities which diminish the blood flow to the lung through the pulmonary arteries, which subsequently causes dilation of the bronchial arteries, acting as collateral branches. Table 6.

 

 

Table 6
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

An interesting case is the patient shown in Fig. 17 and Fig. 18, who was diagnosed of an agenesis of the right pulmonary artery. It caused dilation and hypertrophy not only of the homolateral bronchial circulation, but of other systemic arteries as well, all responsible of lung perfusion.

 

 

Fig. 17: Vicarious pattern. Patient with right pulmonary arterial and venous agenesis and pulmonary sequestration in the lower right lobe. A. PA chest radiograph. The right lung is reduced in volume. Please notice that its vasculature does not follow a tree-shaped and centrifuged distribution, as seen on the contralateral lung. B. detail of the previous radiograph. Left pulmonary vasculature demonstrates a disrupted net, due to bronchial circulation. C Coronal Maximum Intensity Projection of a contrast-enhanced thoracic CT (lung window). Notice that the left pulmonary vasculature does not follow a tree shaped distribution, as seen on the contralateral lung. D. Coronal Maximum Intensity Projection of a contrast-enhanced thoracic CT (mediastinal window). We can see the right bronchial artery and a branch of the thoracic-abdominal aorta (arrowheads), the latter responsible of the irrigation of the pulmonary sequestration.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Fig. 18: Vicarious pattern. Contrast enhanced CT of the same patient as show in fig.17. Right pulmonary artery agenesis (black arrowhead). Notice as well an enlarged right bronchial artery (white arrowheads).
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

It is important to remember and consider that different pulmonary vascular patterns may be seen on the chest radiograph of a single patient, as different entities might coexist. We can see two examples in the cases shown in Fig. 19 and  Fig. 20.

 

 

Fig. 19: Mixed pattern of venous redistribution pattern and pulmonary arterial hypertension pattern. PA chest radiograph of a patient with pulmonary hypertension and mitral regurgitation treated with mitral valve replacement. Notice a pulmonary arterial hypertension pattern, which consists in enlargement of the central pulmonary vasculature, increased pulmonary trunk and mild amputation of peripheral vessels.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

Fig. 20: Mixed pattern of pulmonary hypertension and overcirculation. A and B. PA chest radiograph of a patient with patent ductus arteriosus, aortic stenosis and pulmonary hypertension. There is an increase in the width of the pulmonary vessels of central predominance (white arrowheads), due to pulmonary hypertension pattern. Nevertheless, there are some peripheral vessels which are enlarged as well, mostly visible on the lateral view (black arrowhead), due to patent ductus arteriosus and, hence, overcirculation. C and D. PA chest radiograph of the same patient as shown in A and B, after surgical treatment of the patent ductus arteriosus. Overcirculation has improved, as seen on the peripheral vessels, which are now normal in size. However, pulmonary central vessels are still enlarged, but less than described in previous radiographs.
References: Radiodiagnóstico, Hospital Clínico San Carlos - Madrid/ES

 

 

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