Z lines in a dog: these hyperechoic stripes don’t move with the lung during respiratory movements. My impression is that they are commoner in older animals and in cats more than in dogs. However, there is a tendency for them to become more prominent with increasing fibrosis or inflammation. Hence, they are not as reliably indicative of pathology as B lines. Some I lines may be seen in ‘normal’ lung, especially with a high frequency probe and towards the margins of lobes. I tend to prefer using a 10 MHz linear probe and, with this, they are much more commonly apparent than with a microconvex probe. It is important to note that these become much more apparent when high-frequency probes are used. They also move with the lung on respiration. I lines are short lines arising at the pleura which, unlike B lines, fade as they run deeper. Sonographic interstitial syndrome: the sound of lung water.Īs time has gone by other subgroups of ‘comet-tail’ artifact have been described: B lines arise at the pleura run to the bottom of the image, obscure the normal A lines and move with respiratory movements.Ī wide spectrum of pathologies may cause IS: from left-sided congestive heart failure, overhydration, trauma, pneumonitis, interstitial fibrosis, near-drowning, acute respiratory distress syndrome, lung lobe torsion, electrocution to drug reactions and disseminated neoplasia. Interstitial syndrome: multiple B lines in the lung of a dog. This much we have understood for a while. B lines arise at the pleura, run down to the limit of the image, move with the respiratory movements of the lung and overlie the normal A lines. This provides the conditions for reverberation which causes B lines which are the hallmark of the syndrome. The term ‘interstitial syndrome’ (IS) describes the sonographic appearance of lung in which there is increased extra-vascular water content (oedema) interspersed with air-filled alveoli. These all arise from short-path reverberations within confined spaces. These are the result of sound bouncing back and forth between probe head, pleura and tissue planes in the thoracic wall.Ĭomet-tail artifacts is the generic term for lines which run perpendicular to the pleura: subgroups include B lines, C lines, E-lines, I lines and Z lines. Normal transthoracic lung ultrasound reveals a pattern of repetetive artifactual ‘ A lines‘ all parallel to the pleura. In this post I want to look at the classification of lung lines and their significance. Having arrived in our tool-kit in the last 10 years, this is still an evolving field. The facility to diagnose rapidly, and with high degree of confidence, pneumonia, pulmonary oedema, contusions, pneumothorax and neoplasia is a phenomenal advance. I reckon lung ultrasound must be one of the most profound developments in veterinary medicine during my career. Lung ultrasound: contusions, interstitial syndrome, A, B, C, E, I and Z-lines explored
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