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There is a large fat opacity obliterating the entire left hemi thorax. This space occupying lesion displaces the heart to the right of the midline. On the lateral view, the heart is well seen and considered mildly enlarged as highlighted by the fat opacity between the heart and the sternum. However, it is poorly defined on the VD projection and displaced over the area of the right middle lung lobe. Several irregular, somewhat linear, areas of soft tissue opacity, representative of severely atelectatic left lung lobes are noted to the right of the midline on the VD projection. This results in an inhomogeneous opacity of the caudal lung lobes on the lateral view. The dorsal aspect of the diaphragm on the lateral view and the left diaphragmatic crus are poorly seen.
Findings are representative of a diaphragmatic herniation of a large volume of mesenteric fat. The amount of fat is such that displaces the heart to the right of the midline and causes severe atelectasis and displacement of the left lung lobes to the right hemithorax.
Surgery to address the diaphragmatic herniation is indicated. A thoracic non-cardiac ultrasound or a CT of the thorax to confirm the finding can be performed but are not considered critical.
This case was considered one of the most challenging cases of the section. Successful candidates were able to recognize the mass effect caused by the herniated tissue on the heart and correctly determine that the herniated tissue was of a fat density. Successful candidates were also quick in associating the lack of visualization of the diaphragm with the possibility of a herniation. Unsuccessful candidates fell into three categories: 1) those who recognized the fatty characteristics of the tissue but choose to ignore the significance of the roentgen sign and concluded fluid was present, 2) those who could not discern the mass effect caused by the herniated fat onto the heart and 3) those who concluded that the the lack of visualization of normal lung parenchyma was the result of pleural effusion.
©2013 American College of Veterinary Radiology