Right Middle Lobe Collapse |

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Introduction

The right middle lobe (RML) is the odd one out- there is no left middle lobe as such. The lingula segment of the left upper lobe is the equivalent of the RML. This is worth bearing in mind as the plain film pathology appearances of these lobes can be characterised similarly.

The Right Middle Lobe Anatomy

The right middle lobe has two pulmonary segments which are situated side by side; the more lateral segment, approximates the size of its adjacent neighbor ( medial segment). The medial segment abuts the right heart border medially , while lateral segment extends to and comprises a portion of the lateral border of the right lung. http://lib.cpums.edu.cn/jiepou/tupu/atlas/www.vh.org/adult/provider/radiology/LungAnatomy/RightLung/RtLungSegAnat.html.

When viewing chest radiographs with pathology involving the right middle lobe, it is important to think about the shape and position of the RML in three dimensions. This may not be easy at first. Note the description of the lobes is very approximate. When you look at the position of the RML on the PA image above, it doesn't look very middle-like. The lateral view image gives a better appreciation of its middleness. Further information on lung anatomy here

Important Characteristics of all Lobar Collapse

1.Collapse and consolation can occur independently or together

2.Collapse can be partial or complete

3.It is often not clear to what extent the appearance is due to collapse or consolidation or both. The degrees of each are often unclear.

4.If a lobe is only partially collapsed and there is no accompanying consolidation, there may be no increase in opacity

5.In cases of pure collapse, only when the collapse is virtually complete will there be a significant increase in density of the affected lung

Plain Film Appearance

The plain film appearance of collapse of the right middle lobe is often characterised by a loss of volume, an increase in density, and a loss of clarity of the right heart border.

A partial RML collapse can be difficult to appreciate because the increase in opacity of the lobe is superimposed over the heart shadow

A collapse of the lingula segment of the left upper lobe (LUL)

If there is sufficient collapse of the RML, the horizontal fissure may be pulled down with the collapsing lobe. This will not always be evident given that the horizontal fissure is not always demonstrated.
The child has abnormal opacity in the region of the RML. There are air bronchogram lines and these bronchii appear have a sudden change in calibre and to be displaced medially.

The lateral view is often the confirming image when there is RML collapse. The RML may appear dense with collapse of the lobe and movement of the fissures.
Not unlike RUL collapse, the fissures are attached at the hilum and the RML collapse appears like a fan being closed.

If there is sufficient collapse of the RML, the horizontal fissure may be pulled down with the collapsing lobe. This will not always be evident given that the horizontal fissure is not always demonstrated.	The child has abnormal opacity in the region of the RML. There are air bronchogram lines and these bronchii appear have a sudden change in calibre and to be displaced medially.
The lateral view is often the confirming image when there is RML collapse. The RML may appear dense with collapse of the lobe and movement of the fissures.	Not unlike RUL collapse, the fissures are attached at the hilum and the RML collapse appears like a fan being closed.

an appreciation of the collapse of the RML can be gained by consideration of the normal position of the horizontal and oblique fissure


	an appreciation of the collapse of the RML can be gained by consideration of the normal position of the horizontal and oblique fissure

False RML Collapse

This looks similar to a RML collapse. There is loss of the visualisation of the right heart border and the diaphragm is still seen, although the appearance is complicated by a right sided pleural effusion with a subpulmonic component. The increased density over the thoracic vertebra suggests that this is a collapse/consolidation of the superior segment of the RLL


This looks similar to a RML collapse. There is loss of the visualisation of the right heart border and the diaphragm is still seen, although the appearance is complicated by a right sided pleural effusion with a subpulmonic component.	The increased density over the thoracic vertebra suggests that this is a collapse/consolidation of the superior segment of the RLL

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