Thoracic Ultrasonography Making Diagnosis Easy

Thoracic ultrasonography is a non-invasive diagnostic tool for respiratory issues in dogs as well as cats. It is also known as thoracic point-of-care ultrasound (T-POCUS), which is extremely useful in emergency and critical care settings. Your pet is made to lie on its right or left side, and the ultrasound probe is placed across the ribs to check the chest. The probe is then moved along the chest wall to look for any issues. This real-time scan helps the vet detect problems in the lungs and the area around them (pleura).

Key ultrasound findings of thoracic ultrasonography

Pleural line /Bat sign

The “bat sign” in lung ultrasound is a normal anatomical landmark used to orient the image and confirm that the probe is correctly positioned on the lung. It is formed by the pleural line and the acoustic shadows created by the adjacent ribs, which together resemble a bat with outstretched wings. The pleural line observed between two rib shadows is a normal finding, a bright, horizontal, hyper-echoic line representing the interface between the chest wall and the aerated lung.

Glide sign /Lung sliding /Shimmer sign

When your pet breathes, the chest lining (parietal pleura) and the lung surface lining (visceral pleura) slide smoothly over each other. On ultrasound, this looks like a shimmering or sliding motion, called the glide sign. If the glide sign is present along with bright horizontal lines (A-lines), it means the lungs are healthy and dry.

• A-lines –These are bright, horizontal, evenly spaced lines seen on ultrasound. They show normal, air-filled lungs.
• B-lines –Also called “lung rockets” or “comet-tail artefacts,” these are vertical bright lines that extend deep across the screen and move with breathing. They appear when fluid and air are next to each other in the lungs. A few B-lines can be normal, but if there are more than three, it may indicate lung disease such as fluid build-up or other problems in the lung tissue.

Shred sign / Tissue-Like Sign

An indicator of consolidation (pneumonia), where the lung appears to be shredded, fragmented, or irregular pleural line. A shred sign indicating the presence of consolidated lung tissue.

Thoracic ultrasound helps to diagnose various thoracic conditions, such as pleural space and lung abnormalities.

Pleural space affections

• Pleural Effusion – Fluid accumulation in the pleural space (around the lungs). The patient shows difficulty in breathing, paradoxical breathing, and on ultrasound, an anechoic fluid collection is observed in the chest cavity. If pleural fluid is present, thoracic sonography-guided fluid evacuation can be done, called thoracocentesis.
• Pneumothorax –Air in the pleural space because of trauma. On thoracic ultrasound, the absence of the gliding sign/lung sliding along the pleural line and B lines confirms pneumothorax.

Lung parenchyma affections

• Pneumonia –Inflammation and consolidation within lung tissue. B-lines, i.e., comet tail artefacts, can be observed.
• Pulmonary Edema –Fluid buildup in the lungs, B lines observed at the fluid-air interface. Cardiogenic pulmonary edema occurs because of heart failure; the B lines are observed at the perihilar area of the lung lobes. Non-cardiogenic pulmonary edema occurs because of various reasons, i.e., severe forms of pneumonia, aspiration pneumonia, trauma, etc. In such conditions, multiple or coalescing B lines appear.
• Pulmonary Masses –Tumour tissue in the lung can be diagnosed on Thoracic Ultrasound. (Confirmatory diagnosis can be done on CT) Thoracic ultrasound is an advanced imaging modality; these examinations can provide the clinician with immediate actionable information at minimal risk to the patient, minimal time required to perform the thoracic ultrasound, minimal restraint of animal during ultrasound, and no radiation involved.

(Dr. Snehal Pundkar – God’s Grace Animal Clinic, Komothe, Navi Mumbai)