SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
inspiration and expiration, evaluating movement of the visceral pleural lung surface
relative to the parietal pleural surface of the thoracic wall and diaphragm. If movement
of the lung across the parietal pleural surfaces is rough or erratic, a dry pleuritis is
probably present. Absence of any movement between these surfaces during
respiration is also an indication of a dry pleuritis or adhesions between parietal and
visceral pleural surfaces, but is occasionally seen in normal horses taking very shallow
breaths.
Pulmonary Abnormalities
Compression atelectasis
Compression atelectasis occurs whenever the lung parenchyma is collapsed by fluid,
air, or viscera (in horses with diaphragmatic hernia) occupying space normally
containing lung. The compressed lung is collapsed and smaller airways are no longer
aerated, leaving this portion of lung hypoechoic (echogenicity of soft tissue). The
atelectic lung is retracted towards the hilus. Linear air echoes may be imaged in larger
airways and appear crowded together as they converge towards the root of the lung.
Normal lung is also lighter than fluid and floats on top of and within pleural fluid.
Consolidation
The earliest sign of consolidation may be dimpling or an irregularity of the visceral
pleural surface of the lung, a nonspecific change caused by nonuniform aeration of the
lung periphery. B lines or lung rockets, previously known at comet tail artifacts, radiate
from these nonaerated areas.
In horses with pneumonia, sonolucent areas
representing pulmonary parenchymal consolidation appear, surrounded by normally
aerated lung. These areas of pulmonary parenchymal consolidation usually have an
irregular margin with hyperechoic artifacts deep to the lesion which mimic acoustic
enhancement. Small consolidated areas may be imaged only during exhalation
because the lesion moves underneath the adjacent rib, or inhaled air entering the
surrounding airways and alveoli intervenes, reflecting the ultrasound beam and
preventing their visualization.
The ultrasonographic diagnosis of pulmonary
parenchymal consolidation is based upon the detection of sonolucent pulmonary
parenchyma and visualization of one or more of the lung's anatomical features:
sonographic air bronchograms, sonographic fluid bronchograms, pulmonary vessels, or
scattered echogenic foci due to residual air in consolidated lung parenchyma.
Sonographic air bronchograms are imaged as distinctive hyperechoic linear air echoes
in sonolucent lung. These hyperechoic linear echoes correspond to the traditional air
bronchograms detected on thoracic radiographs. These strongly echogenic branching
lines of the air-filled bronchi converge towards the root of the lung, becoming larger as
they merge.
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