Lobar collapses

17 Lobar collapses

Background

Collapse of the five lung lobes (right upper, middle and lower, left upper and lower) produces characteristic appearances on a CXR. Interpretation requires a good knowledge of lobar anatomy and of silhouette signs (see Page 5).

Lobar collapses are important as they are a common presentation of bronchial carcinoma (see Chapter 15). Other causes of lobar collapse include any process that obstructs a main bronchus, including mucus plugging in asthmatics and postoperative patients, foreign bodies and ET tubes (these usually cause complete collapse; see Chapter 2).

General radiological features common to all collapses

• A radiological hallmark of all collapses is loss of lung volume on the affected side, which worsens in chronic collapse – if the collapse is acute there may be no loss of volume.
• The ribs may come closer together when volume is lost on one side.
• Volume loss may also result in a tented raised hemidiaphragm on the side of the collapse.
• There may be mediastinal shift toward the collapsed side.
• Look for a mass at the hilum, which would increase suspicion of a tumour as the cause. However, a tumour may be present and not seen due to the collapse and any new unexplained collapse warrants further imaging/investigation.
• The remainder of the lung on the side of the collapse may be more lucent than that on the opposite side, with a decreased vessel count.

Remember to use the silhouette sign to your advantage.

A collapsed lobe is of increased density. Remember that edges are only seen on films if two structures of different density are next to each other. In lung collapse a lobe effectively becomes water/soft tissue dense. So if an edge you would expect to see disappears this might help you determine which lobe is collapsed.

For example, in left lower lobe collapse, the left lower lobe is adjacent to the left hemidiaphragm. When this lobe collapses the contour of the left hemidiaphragm is no longer seen.

Collapsed lung is generally homogeneous in density – with no air bronchograms seen.

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Aug 20, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on Lobar collapses

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