Consolidation:
Functionally the pulmonary airways can be divided into two groups. The proximal airways function purely as a conducting network: the airways distal to the terminal bronchioles are also conducting structures, but more importantly, are the site of gaseous exchange. These terminal airways are termed acini, an acinus comprising respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli arising from a terminal bronchiole. Consolidation implies replacement of air in one or more acini by fluid or solid material, but does not imply a particular pathology or aetiology. The smallest unit of consolidated lung is a single acinus, which casts a shadow approximately 7 mm in diameter. Communications between the terminal airways allow fluid to spread between adjacent acini, so that larger confluent areas of consolidation are generally visible and are frequently not confined to a single segment.
The commonest cause of consolidation is acute inflammatory exudate associated with pneumonia. Other causes include cardiogenic pulmonary edema, non-cardiogenic pulmonary edema, haemorrhage and aspiration. Neoplasms such as alveolar cell carcinoma and lymphoma can produce consolidation and alveolar proteinosis is a rare cause. In an individual patient, consolidation may be due to more than one basic aetiology. For example, a patient with major head trauma may be particularly susceptible to infection, aspiration and non-cardiogenic pulmonary edema.
When consolidation is associated with a patent conducting airway, an air bronchogram is often visible. This sign is produced by the radiographic contrast between the column of air in the airway and the surrounding opaque acini. If consolidation is secondary to bronchial obstruction, however, the air in the conducting airway is resorbed and replaced by fluid, and the affected area is of uniform density.
The volume of purely consolidated lung is similar to that of the normal lung since air is replaced by fluid or solid. However, collapse and consolidation are often associated with one another. When consolidation is due to fluid, its distribution is influenced by gravity, so that in acute pneumonitis, consolidation is often denser and more clearly demarcated inferiorly by a pleural surface, and is less dense and more indistinct superiorly.
Lobar consolidation:
Consolidation of a complete lobe produces a homogenous opacity possibly containing an air bronchogram, delineated by the chest wall, mediastinum or diaphragm and the appropriate interlobar fissure or fissures. Parts of the diaphragm and mediastinum adjacent to the non-aerated lung are obscured.
Right upper lobe consolidation:
This is confined by the horizontal fissure inferiorly and the upper half of the oblique fissure posteriorly and may obscure the right upper mediastinum.
Right middle lobe consolidation:
This is limited by the horizontal fissure above and the lower half of the oblique fissure posterioly, and may obscure the right heart border.
Lower lobe consolidation:
This is limited by the oblique fissure anteriorly and may obscure the diaphragm.
Left upper lobe and lingula consolidation:
These are limited by the oblique fissure posteriorly. Lingula consolidation may obscure the left heart border, and consolidation of the upper lobe may obscure the aortic knuckle.
Functionally the pulmonary airways can be divided into two groups. The proximal airways function purely as a conducting network: the airways distal to the terminal bronchioles are also conducting structures, but more importantly, are the site of gaseous exchange. These terminal airways are termed acini, an acinus comprising respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli arising from a terminal bronchiole. Consolidation implies replacement of air in one or more acini by fluid or solid material, but does not imply a particular pathology or aetiology. The smallest unit of consolidated lung is a single acinus, which casts a shadow approximately 7 mm in diameter. Communications between the terminal airways allow fluid to spread between adjacent acini, so that larger confluent areas of consolidation are generally visible and are frequently not confined to a single segment.
The commonest cause of consolidation is acute inflammatory exudate associated with pneumonia. Other causes include cardiogenic pulmonary edema, non-cardiogenic pulmonary edema, haemorrhage and aspiration. Neoplasms such as alveolar cell carcinoma and lymphoma can produce consolidation and alveolar proteinosis is a rare cause. In an individual patient, consolidation may be due to more than one basic aetiology. For example, a patient with major head trauma may be particularly susceptible to infection, aspiration and non-cardiogenic pulmonary edema.
When consolidation is associated with a patent conducting airway, an air bronchogram is often visible. This sign is produced by the radiographic contrast between the column of air in the airway and the surrounding opaque acini. If consolidation is secondary to bronchial obstruction, however, the air in the conducting airway is resorbed and replaced by fluid, and the affected area is of uniform density.
The volume of purely consolidated lung is similar to that of the normal lung since air is replaced by fluid or solid. However, collapse and consolidation are often associated with one another. When consolidation is due to fluid, its distribution is influenced by gravity, so that in acute pneumonitis, consolidation is often denser and more clearly demarcated inferiorly by a pleural surface, and is less dense and more indistinct superiorly.
Lobar consolidation:
Consolidation of a complete lobe produces a homogenous opacity possibly containing an air bronchogram, delineated by the chest wall, mediastinum or diaphragm and the appropriate interlobar fissure or fissures. Parts of the diaphragm and mediastinum adjacent to the non-aerated lung are obscured.
Right upper lobe consolidation:
This is confined by the horizontal fissure inferiorly and the upper half of the oblique fissure posteriorly and may obscure the right upper mediastinum.
Right middle lobe consolidation:
This is limited by the horizontal fissure above and the lower half of the oblique fissure posterioly, and may obscure the right heart border.
Lower lobe consolidation:
This is limited by the oblique fissure anteriorly and may obscure the diaphragm.
Left upper lobe and lingula consolidation:
These are limited by the oblique fissure posteriorly. Lingula consolidation may obscure the left heart border, and consolidation of the upper lobe may obscure the aortic knuckle.
No comments:
Post a Comment