Lung Ultrasound (Vet BLUE): Telling Cardiogenic from Non-Cardiogenic Dyspnoea
A dyspnoeic patient arrives, and the question on everyone's mind is the same: is this the heart, or is it something else? Radiographs take time, positioning a struggling patient is risky, and auscultation alone often isn't conclusive. Lung ultrasound — known in veterinary circles as Vet BLUE — answers that question in minutes, without moving the patient far from where they're most comfortable.
What Vet BLUE actually is
Vet BLUE (Bedside Lung Ultrasound Exam) adapts human point-of-care lung ultrasound for dogs and cats. Rather than a full thoracic survey, it's a handful of standardised points scanned bilaterally along the chest wall — caudodorsal, perihilar, middle, and cranial lung regions on each side. At each point, you're not looking for detailed anatomy; you're reading a pattern.
The pattern that matters: A-lines vs B-lines
A normal, aerated lung reflects sound in a very characteristic way: horizontal, evenly spaced reverberation artefacts called A-lines. This is the "dry lung" pattern, and it's what you want to see in a patient whose dyspnoea has a non-pulmonary cause.
When the interstitium fills with fluid, a different artefact appears: B-lines — vertical, "comet-tail" lines that arise from the pleural line and sweep to the bottom of the screen, erasing the A-lines beneath them. A few scattered B-lines can be a normal finding in some regions. What matters diagnostically is a pattern of multiple, diffuse, bilaterally symmetric B-lines across most of the scanned points — this is the classic signature of an interstitial-to-alveolar syndrome, and cardiogenic pulmonary oedema is the veterinary cardiologist's leading suspect when this pattern shows up alongside a big left atrium.
The pitfall: B-lines are not a heart failure test
This is the point worth repeating: a diffuse B-line pattern tells you the lung interstitium is wet. It does not, by itself, tell you why. Pneumonia, pulmonary contusion, non-cardiogenic oedema, fibrosis, and neoplasia can all produce B-lines too. The clinical picture that points toward cardiogenic oedema specifically is the B-line pattern plus a relevant history, plus echocardiographic evidence of left heart disease — an enlarged left atrium (LA:Ao), in particular. A focal or asymmetric B-line pattern, by contrast, should make you think harder about a localised process like pneumonia or contusion rather than global cardiac failure.
Where this fits alongside what you already do
If you're already using TFAST in your emergency work-up, Vet BLUE isn't a replacement — it's the piece TFAST doesn't cover. TFAST's chest views screen for pleural and pericardial fluid and pneumothorax; Vet BLUE looks at the lung parenchyma itself. Used together with a focused echo to check LA size, you get a genuinely complete picture of a breathless patient in well under ten minutes, without radiographs and often without any sedation at all.
Building this into your skill set
Reading a lung ultrasound pattern reliably takes structured practice — knowing what counts as "a few normal B-lines" versus a genuinely diffuse pathological pattern isn't something that comes from a diagram alone. This sits naturally alongside both cardiac and emergency point-of-care skills, which is exactly the ground our Echocardiography Course and Emergency Ultrasound Course cover between them.
Want your whole team confident reading a breathless patient at 2am, not just in daylight hours? Take a look at our in-practice CPD courses — delivered on-site, on your own machine, with your own cases.
