Page 2335 - Cote clinical veterinary advisor dogs and cats 4th

1156 Radiographic Interpretation, Thorax

• Vertebral heart score can be used to objec- Lung: not enough to cause effacement of the
pulmonary vessels or silhouetting.
tively assess cardiac size (p. 1187). • A lesion in dependent lung lobes may ○ Many artifacts can cause an unstructured
VetBooks.ir chested) to 3.5 (round-chested) intercostal lung and not be seen. In a nondependent ○ The unstructured interstitial pattern can
• Dog: lateral view, heart length: 2.5 (deep-
silhouette with the surrounding atelectatic
interstitial pulmonary pattern.
position, the lesion will be surrounded by
spaces.
• Dog: VD/DV view, heart width: ≤
aerated lung, allowing its detection.
the thoracic width. 2 3 of • Lung lesions create patterns categorized as be transient, seen early in a disease process
or when a disease is resolving.
• Dog: left atrial (LA) enlargement on the alveolar, bronchial, and interstitial. ○ Severe bronchial disease may lead to a
lateral view leads to a convexity at the • Distinguish further among differential concurrent structured interstitial pattern
caudodorsal aspect of the cardiac silhouette. diagnoses based on lesion location. if airway plugging occurs.
LA enlargement on the VD/DV view may • Recumbent atelectasis is common. Features: Mediastinum:
cause the mainstem bronchi to spread apart. interstitial or alveolar pattern with ipsilateral • Evaluate the position of the mediastinum.
• Cat: heart length = distance from the cranial mediastinal shift Evaluate for structures that are normally seen
aspect of the fifth rib to the caudal aspect • Benign pulmonary osseous metaplasia can and that are not normally seen.
of the seventh rib be distinguished from pulmonary nodules • Pneumomediastinum reveals mediastinal
• Cat: LA enlargement confers a kidney bean based on their small size and mineral opacity. structures that are not normally seen (e.g.,
shape to the heart on the lateral view. LA or • Alveolar pattern brachiocephalic trunk).
biatrial enlargement may create a valentine- ○ Silhouetting (border effacement): increased • Pneumomediastinum can cause pneumotho-
shaped heart on the VD/DV view. pulmonary opacity prevents the clear rax (not vice versa).
• A globoid shape to the cardiac silhouette may demarcation between abnormal lung and • LA enlargement and tracheobronchial
indicate pericardial effusion, right- and left- an abutting soft-tissue–opacity structure lymphadenopathy cause splaying of the
sided cardiac disease, dilated cardiomyopathy, (e.g., cardiac silhouette, body wall). mainstem bronchi; the former causes dorsal
or a peritoneal pericardial diaphragmatic hernia. ○ Lobar sign: increased opacity in an displacement of the trachea, and the latter
• Evaluate the cardiac silhouette, the pul- abnormal lung lobe creates a sharp demar- causes ventral displacement.
monary vessels, and lungs concurrently for cation against an abutting normal lung • If megaesophagus is seen, distinguish seg-
suspicious of left-sided heart failure. Evaluate lobe. mental from generalized dilation to narrow
the cardiac silhouette, caudal vena cava, and ○ Air bronchogram/“trees in the fog”: the differential list.
the abdomen concurrently for suspicion of increased lung opacity (fog) effaces the • Evaluate for tracheal narrowing.
right-sided heart failure. pulmonary vessels, and only the airways Pleural space:
• Hypovolemia (e.g., dehydration, hypoadre- (trees) can be distinguished. • Pleural effusion
nocorticism) may cause microcardia. • Bronchial pattern ○ VD view (rather than DV) allows better
Vessels: ○ Faint airway markings are normal. assessment of the cardiac silhouette when
• Caudal vena cava diameter varies with the ○ Thickened airways create the appearance effusion is present.
cardiorespiratory phase but should be similar of doughnuts and tram tracks when the ○ Pleural fissure lines and retraction of
to aortic diameter. airways are viewed end-on or from the the lung lobes that results in a scalloped
• A pulmonary artery and its corresponding side, respectively. appearance along the lung periphery.
vein should be similar in diameter when • Interstitial pattern • Pneumothorax
measured at the same level. The cranial ○ Structured interstitial pattern: soft-tissue– ○ Cardiac silhouette separated from the
pulmonary vessels are best evaluated on the opacity nodules that can be various sizes, sternum on the lateral view. A space exists
left lateral view. ranging from miliary (pinpoint) to nodules between the lung lobe and the body wall
• On the lateral view, the cranial pulmonary (<2 cm in diameter). Structures > 2 cm where normal bronchial markings are not
vessels should be smaller than the diameter are masses. seen.
of the proximal fourth rib. ○ Unstructured interstitial pattern: a mild ○ Pneumothorax with a contralateral medias-
• On the VD/DV view, the caudal pulmonary increase in pulmonary opacity that tinal shift indicates tension pneumothorax.
vessels normally may be up to 1.2 times the causes difficulty in seeing clear margins Emergency thoracocentesis is warranted
diameter of the ninth rib. to the pulmonary vessels. The opacity is (p. 1164).
Body wall and abdomen:
• Assess the diaphragm and other musculo-
skeletal structures for evidence of trauma,
Causes of an Alveolar Pulmonary Pattern congenital diseases, neuromuscular disease,
or neoplasia.
Cause Distribution* Prevalence
Pneumonia Ventral Common
Cardiogenic pulmonary edema Variable Common
Noncardiogenic pulmonary edema Dorsocaudal Less common Causes of a Bronchial Pulmonary Pattern
Hemorrhage Cause Prevalence
Trauma Variable Common
Coagulopathy Variable Less common Allergic airway disease Common
Thromboembolism Variable Less common Infection
Bacterial Less common
Atelectasis Variable Common Parasitic Rare
Allergy (eosinophilic) Variable Rare Chronic irritation Less common
Primary lung tumor Variable Rare Cardiogenic pulmonary edema Less common
*Disease distributions are generalizations, and the specific distribution of any disease leading to an Diffuse tumor Rare
alveolar pattern is variable.
From Thrall DE: The canine and feline lung. In Thrall DE, editor: Textbook of veterinary diagnostic From Thrall DE: The canine and feline lung. In Thrall DE, editor: Textbook of veterinary diagnostic
radiology, ed 6, St. Louis, 2013, Saunders. radiology, ed 6, St. Louis, 2013, Saunders.

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