One of the most common tasks facing veterinary clinicians is the interpretation of radiographs. Chest radiography and its assessment can be especially complicated if we are not clear about radiological patterns and basic thoracic anatomy. Here is a brief summary of what you will find by accessing the full webinar given by Carlo Anselmi, Dip. ECVDI and Maria Frau, LV and radiologist at Pride Veterinary Hospital, UK.
Radiological anatomy
Both dogs and cats have four pulmonary lobes on the right side (cranial, middle, caudal and accessory) and two on the left side (cranial and caudal). The four anatomical components of a lung lobe are: alveolus (aerated component), bronchi/bronchioles, blood vessels and interstitium.
Lung patterns
The identification of lung patterns represents the lung compartment that is most affected radiologically. The patterns we can recognise are: bronchial, interstitial, alveolar, vascular and mixed.
Bronchial pattern
Bronchial pattern represents infiltration of cells or fluid into the bronchial wall or peribronchial space. Radiographically it results in an increased number of «doughnuts» and «train tracks».
Interstitial pattern
The interstitial pattern can be divided into two categories: structured and unstructured.
- Structured interstitial pattern: refers to the presence of at least one pulmonary nodule. Differentiating a pulmonary nodule from the cross-section of a pulmonary vessel can be difficult and lead to misdiagnosis.
- Unstructured interstitial pattern: this is due to the excessive presence of fluid or cells in the lung interstitium in a uniform pattern, in which the pulmonary vessels remain visible.
Alveolar pattern
The alveolar pattern consists of the replacement of air in the alveolus by fluid or less frequently by cells, resulting in increased opacity of the lung and loss of visualisation of the pulmonary vessels. One of the radiographic findings that indicate the presence of an alveolar pattern is the detection of air bronchograms. Another indication of an alveolar pattern is the detection of the so-called lobar sign.
Correct identification of each of these allows a differential diagnosis to be established and thus better target diagnostic tests and/or treatment of the patient.
Vascular pattern
The vascular pattern refers to the evaluation of the main arteries and veins. An increase or decrease in these can indicate whether the patient has cardiac or extracardiac disease.
Mixed patterns
Actually, the vast majority of pulmonary pathologies involve more than one lung compartment, resulting in a mixed pattern. At the same time, one pulmonary pattern may mask a second. Therefore, the clinical history together with radiographic findings should always be taken into account to formulate our more specific differential diagnosis.
