image of Thorax
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Non-cardiac thoracic ultrasonography complements radiography in the examination of patients with chest wall, pleural space, mediastinal and pulmonary disease. Since ultrasound waves are reflected at soft tissue-gas interfaces, indications for non-cardiac thoracic ultrasonography include evaluation of peripheral lesions that are not surrounded by air, or thoracic diseases that are associated with pleural effusion. This chapter covers indications and the value of ultrasonography compared with radiography and computed tomography, before moving on to imaging technique and normal ultrasonographic appearance. Thoracic wall lesions, rib lesions and fractures, pleural space disease, mediastinal masses, diaphragmatic rupture and herniation and lung lobe conditions are all addressed. This chapter includes six video clips.

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5.1 Transducer placement for different scan windows. A = thoracic inlet window; B = transverse intercostal window; C = long-axis intercostal window; D = substernal, transhepatic window.
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5.2 Long-axis view of the chest wall of a normal Cairn Terrier using a linear transducer. The lung surface is seen as a smooth, straight hyperechoic line (arrowed). The superficial soft tissues have a striated appearance consistent with layers of fat, muscle fibres and fascial planes. A rib (*) is seen in cross-section: it has a smooth, curved surface and creates a distal shadow.
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5.3 Ultrasonogram of an 8-year-old male neutered Golden Retriever with a thoracic wall mass. The transducer is aligned with the long axis of the 7th rib. Dorsal is to the left of the image. The proximal portion of the rib is normal with a smooth hyperechoic surface (black arrows); the distal portion of the rib is surrounded by a large hypoechoic mass (white arrowheads). The bone surface of the distal portion of the rib is interrupted and very irregular, consistent with lysis and periosteal reactions. Biopsy of the mass revealed a poorly differentiated sarcoma.
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5.4 Thoracic ultrasonogram of a 6-year-old neutered Australian Shepherd bitch. The 7th and 8th ribs are seen in cross-section. The 8th rib is much larger in diameter than the 7th, but has a smooth surface and no associated soft tissue mass. This is consistent with callus formation following rib fracture. The dog had sustained thoracic trauma several months prior to this ultrasound examination.
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5.5 Ultrasonogram of the cranial pleural cavity of a 3-year-old male neutered mixed-breed dog with pyothorax. There is a large amount of very cellular pleural fluid present. The lung lobes are partially collapsed and there are multiple fibrin tags seen along the pleural surface (arrowed).
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5.6 Long-axis view of the cranioventral thorax of a 6-year-old male neutered Borzoi with chronic idiopathic chylothorax. Note the round pockets of fluid separated by thick hyperechoic fibrin strands.
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5.7 Long-axis view of the cranial thorax of a 10-year-old female neutered Domestic Shorthaired cat. Bilateral pleural effusion is present (*). The cranial mediastinum is thickened and contains multiple enlarged, hypoechoic lymph nodes (arrowed). The cranial lung lobes are partially collapsed and very rounded. The cat was diagnosed with idiopathic chylothorax. Histopathology showed reactive hyperplasia of the lymph nodes.
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5.8 An 8-year-old neutered Labrador bitch was presented for regurgitation. Megaoesophagus and a cranial mediastinal mass were seen radiographically. On ultrasound examination of the cranial mediastinum, a large heterogenic mass with multiple cavitations was seen. Thymoma was diagnosed on cytology.
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5.9 Ultrasonogram of the cranial mediastinum of an 18-year-old female spayed Domestic Shorthaired cat presented with lethargy and icterus. Liver neoplasia was subsequently diagnosed. On thoracic radiographs a cranial mediastinal mass was observed. Ultrasonographically there are two hypoechoic, thin-walled cystic structures seen cranial to the heart with distal acoustic enhancement (arrowed) of the larger structure. Cranial mediastinal cysts, unrelated to the liver disease, were diagnosed.
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5.10 Long-axis view of the caudal mediastinum of a 16-year-old male neutered Persian cat with squamous cell carcinoma in the accessory lung lobe and metastasis into the caudal vena cava (CVC) diagnosed on necropsy. The accessory lung lobe mass is labelled. A second hypoechoic mass (arrowed) is seen in the caudal mediastinum, extending into the caudal vena cava (double-headed arrow). Pleural effusion is also present.
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5.11 Ultrasonograms of the caudoventral thorax of a cat and a dog with traumatic diaphragmatic hernia. In the cat, the liver and gallbladder (GB) have herniated into the thoracic cavity; some of the liver lobes are adjacent to the heart and surrounded by echogenic pleural effusion (haemorrhage). In the dog, the spleen and some small intestinal (SI) loops are seen adjacent to the heart. Pleural effusion is also present.
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5.12 Long-axis view of the thorax of an 18-month-old Domestic Shorthaired cat presented forlethargy and coughing. Multiple areas of focal consolidation are seen in the periphery of the lung lobes (arrowheads). Some of the consolidations create ring-down artefacts (arrowed) seen as a narrow strip of densely spaced hyperechoic lines. infection was the final diagnosis.
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5.13 Ultrasonogram of the cranial lung lobe of an 11-week-old Dogue de Bordeaux bitch presented for dyspnoea and vomiting. The lung lobe is partially consolidated but hyperechoic foci consistentwith residual air in the airways or alveolar space areseen throughout the lobe. Necrotizing pneumonia wasthe final diagnosis.
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5.14 Lung lobe atelectasis in a dog with a large volume pleural effusion. The lung lobe is collapsed to a thin triangular structure (arrowed). The hyperechoic foci in the centre represent gas-filled bronchi.
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5.15 Long-axis view of the thorax of a 3-year-old male neutered Domestic Shorthaired cat with pulmonary adenocarcinoma. The affected lung lobe is distorted and contains a hypoechoic mass (*). The tip of the lung lobe is surrounded by cellular effusion due to carcinomatosis (arrowed).
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5.16 Power Doppler ultrasonogram of a pulmonary mass in a 9-year-old male neutered Poodle. The mass is hypoechoic, well delineated towards the aerated lung tissue (hyperechoic) and is well perfused. Pulmonary carcinoma was diagnosed with fine-needle aspirates.
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5.17 A 2-year-old Weimaraner was presented for lethargy, fever and coughing. Pleural effusion and a mass lesion in the right caudal lung lobe were seen radiographically. On ultrasound examination, a fluid-filled mass with a thick hyperechoic capsule (arrowed) was seen. The lung lobe was resected and a pulmonary abscess was diagnosed.
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5.18 Metastatic pulmonary disease in an 11-year-old neutered Labrador Retriever bitch. Two hypoechoic nodules are seen on the surface of the lung (arrowed). Nodules deeper in the parenchyma are obscured by the air-filled lungs.
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5.19 Ultrasonogram of a 9-year-old male neutered Pug with torsion of the left cranial lung lobe. The rotated lung lobe is very hypoechoic, enlarged and contains multiple hyperechoic speckles, consistent with trapped gas (arrowheads). The tubular hypoechoic structure with hyperechoic walls (arrowed) represents a fluid-filled bronchus. No blood flow could be detected in this lung lobe with Doppler ultrasonography and the diagnosis of lung lobe torsion was confirmed during surgery.


Normal lung.

Long-axis view of the thorax of a Beagle without clinical signs of respiratory disease. Note how the hyperechoic lung surface slides against the chest wall during inspiration and expiration in this panting dog.

Pleural fluid.

Long-axis view of the cranial thorax of a cat with a large volume of pleural fluid (transudate). The heart is visible on the right side of the image. The hyperechoic line running horizontally across the image represents the normal slender cranial mediastinum. Both cranial lung lobes are collapsed and are seen as bands of non-aerated tissue on each side of the mediastinum.

Pulmonary mass (1).

Clip showing a peripheral pulmonary adenocarcinoma in a cat. The heart is visible on the right side of the image. The mass is very superficial, just inside the chest wall on the left of the image. As the cat breathes in, small hyperechoic speckles are observed within the mass, consistent with gas in the airways. This finding confirms that the mass is pulmonary in origin.

Pulmonary mass (2).

This clip shows the lung surface of a 10-year-old male neutered Rottweiler with metastatic osteosarcoma. Note the small hypoechoic nodule moving with respiration just below the lung surface.

Lung lobe torsion.

Ultrasound examination of the thoracic cavity of a 6-year-old Borzoi bitch with torsion of the left cranial lung lobe. Pleural fluid surrounds the lobe, which is enlarged and hypoechoic with scattered hyperechoic patches representing gas.

Fine-needle aspiration of a pulmonary mass.

In this clip the heart lies on the left of the image, with an irregularly rounded hypoechoic mass on the right. The needle is seen as a hyperechoic linear structure entering the mass from the top right of the image. Precise needle placement requires experience and an immobilized patient (preferably under general anaesthesia).

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