Right Lower Lobe Consolidation

Introduction

Right Lower lobe (RLL) is a relatively common site for consolidation and can be missed if a lateral view is not included in the series.

The Meaning of the Term Consolidation

One of the unfortunate aspects of the term consolidation is that its meaning can be different depending on who is using the term. When a clinician uses the term consolidation he/she is usually referring to a consolidation associated with acute pneumonia. Thus, the term consolidation and pneumonia have very similar meanings and are almost used interchangeably.

Strictly speaking, the term consolidation does not imply any particular aetiology or pathology. Acute pneumonia is the commonest cause but not the only cause of consolidation. ( other causes include chronic pneumonia, pulmonary oedema and neoplasm). Thus when a radiologist has reported a chest X-ray examination and notes the presence of consolidation he/she is simply stating that some of the long airspace has been replaced by a fluid.

Notes on Consolidation

• Refers to fluid in the airspaces of the lung

• Consolidation may be complete or incomplete

• The distribution of the consolidation can vary widely. A consolidation could be described as “patchy”, “homogenous”, or generalised”.

• A consolidation may be described as focal or by the lobe or segment of lobe affected

Loss of Visualisation of the Right Hemidiaphragm

It is widely considered axiomatic that the loss of visualisation the right hemidiaphtragm is a sign of RLL disease. Felson (<a class="external" href="http://www.amazon.com/Chest-Roentgenology-Benjamin-Felson/dp/0721635911/ref=sr_1_2?ie=UTF8&s=books&qid=1252240078&sr=1-2" rel="nofollow" target="_blank">Chest Roentgenology, W.B. Saunders, 1973, p38</a>) has challenged this contention on the grounds that the right hemidiaphragm is widely variable in its shape and could be obliterated by middle lobe disease in some patients.

The Right Lower Lobe Anatomy

adapted from <a class="external" href="http://books.google.com.au/books?id=Bif0zpmEWtAC" rel="nofollow" target="_blank">By Fred W. Wright Radiology of the Chest and Related Conditions: Together with an Extensive Illustrative Collection of Radiographs CRC Press, 2002</a>	The right lower lobe is comprised of five pulmonary segments. It is a large lobe and will provide varying patterns of consolidation depending on which segments are involved.
adapted from <a class="external" href="http://books.google.com.au/books?id=Bif0zpmEWtAC" rel="nofollow" target="_blank">By Fred W. Wright Radiology of the Chest and Related Conditions: Together with an Extensive Illustrative Collection of Radiographs CRC Press, 2002</a>	Note that consolidation of the apical segment will not result in loss of the diaphragmatic outline. Further information on lung anatomy here

Plain Film Appearances of Lung Consolidation

Radiological appearances common to all lobes are:

1.Abnormal lung opacity

2.Increase in the size and number of lung markings

3.Loss of clarity of the diaphragm on the AP and/or lateral views

4.Loss of clarity of the heart border on the AP and/or lateral views

5.Air bronchogram lines

6.Loss of the normal darkening inferiorly of the thoracic vertebral bodies on the lateral view

7.Opacification of the lung behind the heart shadow or below the diaphragms

Plain Film Appearances of RLL Lung Consolidation

•Appears as an area of increased opacity within the RLL •Some loss of the hemi-diaphragm is commonly seen	•Loss of right hemi-diaphragm •Dense opacity in RLL •Some loss of right heart border
•Increased opacity within the RLL •Commonly seen with loss of the right hemi-diaphragm	•Triangular opacity •Loss of right hemi-diaphragm

Case 1

	This 10 year old boy presented to the Emergency Department with a history of fever for 2 weeks. There is increased lung density adjacent to the right heart border (arrowed). Compare the lung density adjacent to the left heart border with that adjacent to the right heart border- they should be a similar density. There is no appreciable loss of clarity of the right heart border (so called silhouette sign) suggesting a RML collapse. There is some loss of definition (silhouette sign) of the medial aspect of the right hemidiaphragm suggesting that the opacity is within the right lower lobe. There is also blunting of the right costophrenic angle.
	The lateral image demonstrates increased density behind the heart shadow (arrowed). This is likely to be airspace opacity (consolidation) within the right lower lobe. One of the useful clues when looking for consolidation on a lateral view is that there should be an even darkening of the vertebral bodies as you look from top to bottom. This image demonstrates vertebral bodies that marginally decrease in density just above the right hemidiaphragm. How do you know if the density is on the right or the left? Just looking at this image it's not easy to tell. If you look carefully, the left hemidiaphragm is preserved and the right is not visualised posteriorly (subtle silhouette sign). More importantly, we know from the consolidation seen on the PA image that the diseased lung is on the right. Always keep a mental picture in you mind of the positions of the fissures- this density is clearly within the RLL. To put this appearance in clinical terms, the patient has RLL pneumonia or pneumonitis which is likely to be treated with antibiotics.

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