The abnormal hilum

Published on 23/05/2015 by admin

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Last modified 22/04/2025

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CHAPTER 6 The abnormal hilum

6.1 Unilateral hilar enlargement 122

6.2 Bilateral hilar enlargement 126

6.1 Unilateral hilar enlargement

This patient has a bulky right hilum. The contour of the right pulmonary artery is not seen separate to it.

The accompanying CT image shows a lobulated mass lesion at the hilum, and consolidation in the lung posterior to the mass, extending backwards to the chest wall. At bronchoscopy this was shown to be due to a bronchogenic tumour.

Hilar enlargement is difficult! Suspect unilateral hilar enlargement if:

1. One hilum is bigger than the other (obviously – they should be the same size!).

2. One hilum is denser than the other.

3. There is a loss of the normal concave shape – the hila are usually concave in shape. This concavity may disappear and be the first sign of hilar enlargement.

If you suspect unilateral hilar enlargement then:

1. Check the technical quality of the film. A rotated film will make one hilum appear larger than another.

2. Look at the lateral film. An enlarged hilum may look abnormally dense on the lateral and sometimes this is easier to spot than on the PA.

3. Look at the old films. You will be less worried if the X-ray looked the same 15 years ago!

Now you need to decide whether the enlargement is due to enlarged vascular shadows or enlargement of the hilar lymph nodes or whether it is due to a central bronchial carcinoma superimposed over the hilar shadow. These are the likely possibilities.

1. Look at the edge of the hilum. Vascular margins are usually smooth in nature. Lymphadenopathy gives a smooth lobular appearance. Spiculated, irregular or indistinct margins suggest malignancy.

2. Look for the presence of calcium which will appear as a very dense white. Its presence suggests lymphadenopathy.

3. Look at the rest of the X-ray. If you suspect hilar enlargement then look carefully at the periphery for lung lesions (tumour, TB), lung infiltration (carcinomatous lymphangitis) or bone lesions (metastases).

4. Look at the rest of the mediastinum. Malignant hilar enlargement may be associated with superior mediastinal lymphadenopathy.

Hilar enlargement always warrants further investigation.

6.2 Bilateral hilar enlargement

In this patient both hilar regions are enlarged. The pulmonary arteries leading away from the hila are normal in size. This indicates that there is lymph node enlargement at both hila. This patient was a 30-year-old man with a skin rash, erythema nodosum, and his diagnosis was sarcoidosis.

As with unilateral hilar enlargement, bilateral hilar enlargement can be due to enlargement of pulmonary arteries, veins or lymph nodes. The features that suggest hilar enlargement are described on page 123. In bilateral enlargement they are present on both sides! The commonest causes of bilateral hilar enlargement are pulmonary hypertension and sarcoidosis. You should start off by looking for features of either of these. If you suspect pulmonary hypertension then:

1. Look at the periphery of the X-ray. Pulmonary hypertension is associated with peripheral pruning which means that the blood vessels appear cut off before they reach the outer ⅓ of the lung. The edge of the lung fields are, therefore, often darker than usual and the central area often whiter.

2. Look at the shape of the hila and lower lobe pulmonary arteries. The lower lobe pulmonary arteries will also be big in pulmonary hypertension but of normal size if hilar enlargement is due to lymphadenopathy. The hila are, therefore, convex in shape in pulmonary hypertension.

3. Look for a cause of pulmonary hypertension. Look for signs of lung disease such as COPD and look carefully at the shape of the heart for chamber enlargement, for signs of left to right shunts or mitral stenosis.

If you suspect sarcoidosis then enlargement of the hilum may be the only finding. However, other features are often present and you should look for:

1. Small nodules. These are between 1.5 and 3 mm in diameter, are mostly found in the perihilar and mid zones, are non-uniform in character, moderately well defined and usually bilateral.

2. Large nodules. These are about 1 cm in diameter, have an ill-defined edge and sometimes coalesce to give larger opacities which may contain air bronchograms.

3. Lines. The X-ray may demonstrate a network of fine lines emanating from the hilar region.

4. Honeycombing. Features of fibrosis may be apparent. Look for these particularly in the upper zones where they are especially common.

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