Right middle lobe consolidation refers to consolidation in part (incomplete) or all (complete) of the right middle lobe.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inflammatory), tissue, or other material.
The list of causes of consolidation is broad and includes:
- pulmonary oedema
- adult respiratory distress syndrome (ARDS)
- interstitial pneumonias
Consolidation is usually obvious on CT, however features can be difficult on chest radiography. Features of right middle lobe (RML) consolidation on CXR include:
- opacification of the RML abutting the horizontal fissure
- indistinct right heart border
- loss of the medial aspect of the right hemidiaphragm
- air bronchograms
- there may also be evidence of some right middle lobe collapse
It must be remembered that the homogeneity of the consolidation will be influenced by any underlying lung disease.
Occasionally with complete lobar consolidation, there may be increased in volume of the affected lobe, rather than the more frequent collapse. When the fissures are outwardly convex, the appearance is referred to as the bulging fissure sign.
A mnemonic to remember the general features of consolidation is A2BC3