Page 333 - WSAVA2018
P. 333

WSV18-0146
DIAGNOSTIC IMAGING
IMPROVE YOUR INTERPRETATION OF RADIOGRAPHIC PULMONARY PATTERNS IN THE CAT
L. Gaschen1
1Louisiana State University, Veterinary Clinical Sciences, Baton Rouge, USA
IMPROVE YOUR INTERPRETATION OF RADIOGRAPHIC PULMONARY PATTERNS IN THE CATLorrie Gaschen, PhD, DVM, Dr.med.vet,, DECVDI
Louisiana State University School of Veterinary Medicine, Baton Rouge, LA
Introduction
After performing a systematic review of the entire thorax, careful scrutiny of the lung can be one of the most challenging parts of analyzing a thoracic radiograph. Using a practical approach to determine if the lung is abnormal or not then making a decision on whether
the air space, the airway is important. Also important to realize is that most all diseases cross the borders of all parts of the lung.
Are patterns important?
The principles of the pulmonary pattern are important, but a lot of stress can be associated with trying to determine the correct pattern so that one can make the correct diagnosis. A better approach is to determine
if the main opacity of the lung is in the air space or
the airway. Most diseases are in one or the other. In between is the interstitium and the interstitium is often involved anyway. Pure interstitial disease is really only sure when structured nodules are present. Unstructured interstitial disease is often very difficult to diagnose as
a sole abnormality. Determining if disease is in the air space or airway is the best way to set a course of action. By creating a best course of action based on which compartment is most affected and then re-assessing
the radiograph at an appropriate time point following treatment is good medical practice.
The normal lung
The normal feline lung is rather lucent with few linear markings, mostly visible centrally. The periphery of the lung is almost devoid of vascular markings. Thinner
body condition makes the lung look hyperlucent and bronchial and vascular markings may be more visible in the periphery. The opposite is true for obesity where the lung has a hazy interstitial appearance due to the opacity of superimposed fat. Both situations make the lung challenging to assess and emphasis on the clinical signs is important for interpretation.
Your Singapore, the Tropical Garden City
Air space disease
The alveoli are filled with air and this allows the vessels and bronchial structures to be sharply marginated and therefore well visible. These structures are extremely small in the periphery of the feline lung and this is the reason the periphery is so lucent. When an increased opacity is identified, the first duty is to determine if it
is effacing the border of any of soft tissue structure.
The margins of the heart, pulmonary vessels, caudal vena cava and diaphragm should be scrutinized first.
If any one or more of those margins are blurred, the pulmonary opacity is likely in the air space: it replaces air with soft tissue and the air no longer outlines soft tissue structures, making them less visible.
Air space disease may be lobar. If the right middle lobe is homogeneously soft tissue opaque and is the only lobe affected, then atelectasis due to lower airway disease
is the likely cause. Aspiration pneumonia is rare in cats and would only be diagnosed if there is a clinical history of vomiting or regurgitation. If the clinical history fits with best with increased respiratory rate and wheezing, then atelectasis is the diagnosis.
Other radiographic features of air space disease are
air bronchograms, consolidated lobes with lobar sign, and patchy opacities that silhouette borders of vessels, heart and diaphragmatic contours. Lobar consolidation is when the entire lobe is homogenously soft tissue opaque and not reduced in volume, with our without air bronchograms. It is usually due to pneumonia, neoplasia or contusion. Atelectasis is collapse of the lobe due
to pleural space disease or bronchial obstruction. The lobe is opaque and there is a decreased volume, and mediastinal shift of the heart to the affected lobe
Common disease categories causing air space disease are pneumonia, edema, hemorrhage, atelectasis, infection, allergic inflammatory disease, and some neoplasia.
Multifocal, ill defined, patchy soft tissue opacities that obscure the airspace and vessels in their surrounding are often due to infection or edema. Fungal pneumonia and cardiogenic edema are the most common of
these, but neoplasia and contusions also have this appearance. Histoplasmosis can also have a patchy ill-defined mixed or airspace pattern as can cardiogenic edema. Other causes of infectious pneumonia are mycobacterial, cryptococcal, blastomycosis, aspirgillosis, toxoplasmosis, paragonimus and aleurostrongylus.1
Lipid pneumonia is less common but consistently seen in cats. Radiographic abnormalities in aleurostrongylus infection are dependent on severity and duration of infection. Early changes of bronchial thickening and small, poorly defined nodules progress to a generalized alveolar pattern in severe cases. After partial resolution of the alveolar pattern, an unstructured, patchy interstitial
          331
            































































   331   332   333   334   335