Normal body condition with a body condition score (BCS) of 4/9. Deeply inspiratory view; cranial diaphragmatic crus level with T13. Mild rotation of the lateral radiograph, left and right costo-chondral junctions not at the same level. Bony structures are normal. The diaphragm is intact. The liver is of homogenous soft tissue opacity.

The caudo-ventral liver margin extends beyond the costal arch (due to the deep inspiration) but is pointed.

The stomach contains food material and gas.

The trachea runs parallel to the spine. The carina is elevated. Mild splitting of the main stem bronchi on the lateral view.

On the dorsoventral (DV) radiograph the main stem bronchi are laterally displaced ; the left main stem bronchus and its continuation into the left lobar bronchus is not visible.
The caudal vena cava (CVC) runs from caudoventral to craniodorsal .

Severe enlargement of the cardiac silhouette is present.
On the lateral view the cardiac silhouette occupies 4,5 intercostal spaces with increased sternal contact; the cardiac silhouette occupies 95% of the thoracic height. The caudal border is straight and there is loss of the caudal waist. Severe tenting/enlargement of the left atrium is present.

On the DV view the cardiac silhouette occupies 90% of the thoracic width. The cardiac silhouette appears almost round . A large bulge is present between 1 to 4 o’clock (point of maximum bulging is at 3 o’clock =region of the left auricle) followed by a slight flattening of the cardiac contour. The caudal aspect of the cardiac silhouette appears rounded. Caudal to the bifurcation the cardiac silhouette shows a centrally increased opacity, with a clear convex border superimposed onto the remaining cardiac silhouette.

The pulmonary vessels are difficult to see. On the lateral radiograph the pulmonary arteries and veins are larger than the proximal third of the third rib and are thus enlarged. On the DV view the caudal lobar vessels are larger than the 9th rib at the intersection of vessels and rib. The veins are slightly larger than the arteries.

The lung shows a generalized increased opacity, esp. in the caudodorsal lung field. Airbronchograms view are visible on the DV.

• Severe, generalized cardiomegaly with a more pronounced left sided enlargement
• Dilated pulmonary vasculature with the veins slightly larger than the arteries
• Alveolar lung infiltrate caudal lung lobes

The course of the CVC and the elongated cardiac silhouette are due to an enlargement of the left ventricle. Loss of caudal waist, double opacity and bulge between 1-4 o’clock are compatible with an enlargement of left atrium and displacment of the left auricle. That there is only mild splitting of the main stem bronchi on the lateral radiograph is most likely due to the mild rotation of the radiograph obscuring the splitting. The lack of visibility of the left main stem bronchus and its continuation into the left lobar bronchus points toward a displacement and compression due to the enlarged left atrium.

The overall round appearance of the cardiac silhouette on the DV radiograph is most likely related to the deep chested conformation with an upright position of the heart. The round caudal aspect can in addition be due to the enlarged left atrium forming the visible caudal contour.
One common cause for enlargement of the left atrium and auricle in an aged dog is degenerative mitral valve disease. Enlargement of the left ventricle can occur secondary to volume overload, as the increased blood volume in the left atrium enters the ventricle during diastole. The impression of an additional right sided cardiomegaly can be artificial due to displacement of the right side of the heart by the severely enlarged left side or can be due to a concurrent tricuspid valve insufficience (degenerative or congenital (latter being less likely)).

The differential diagnosis is dilated cardiomyopathy which can lead to enlargement of all 4 chambers. However, there is flattening of the cardiac contour at the level of the left ventricle (straightening between 4-5 o’clock on the DV view). The enlargement of the left atrium is more severe than that of the left ventricle. Atrial enlargement occurs secondary to eccentric ventricular enlargement (dilatation) in DCM, thus a more severe enlargement of the left ventricle would be expected.

Another differential diagnosis includes congenital mitral valve dysplasia. The advanced age does not exclude a mild form of congenital disease and the changes could represent a late phase of the disease process. The enlargement of the right side of the cardiac silhouette may be due to similar reasons as discussed for degenerative mitral valve disease.

Dilatation of the pulmonary veins in combination with an alveolar lung pattern is compatible with cardiogenic pulmonary oedema due to left heart backward failure as a result of decompensation.

Severe mitral valve insufficiency due to degenerative mitral valve disease with severe enlargement of the left atrium and left ventricle.

Mild tricuspid insufficiency without significant atrial or ventricular enlargement.