2005 Radiology Exam - Thorax Case 1

Objective of the Case
To identify and logically deduce the cause of the increased soft tissue opacity within the lung.

Information Provided to Candidate
1. Signalment: 5 yr MC DSH
2. History: 1 week history of cough and respiratory distress
3. Opposite lateral and ventrodorsal views of the thorax are available.
4. State the radiographic findings.
5. What is your assessment of these findings?
6. Are further imaging studies needed? If so, what are they and why? If no, why not?

See images below. Click to enlarge.

Findings Expected from Candidate
There are at least two soft tissue nodules overlying the plane of the trachea. There is increased soft tissue opacity within the right caudal thorax and a slight mediastinal shift of the heart toward the right. This soft tissue opacity is causing a silhouette sign with the right caudal border of the heart as well as the diaphragm. There is a decrease in the volume of the entire right hemithorax. There is also loss of visualization of the caudal vena cava.

Conclusion Expected from the Candidate
The increased soft tissue opacity within the right caudal thorax is likely a collapsed right caudal lung and accessory lung lobe given the silhouette signs detected as well as the mediastinal shift and loss of volume of the right hemithorax. The nodules within the trachea are likely either due to neoplasia or a granulomatous disease. A likely cause for the atelectasis of the right caudal and accessory lung lobe is due to bronchial obstruction particularly given the presence of the tracheal nodules. The final diagnosis in this case was lymphoma. Additional imaging procedures that could help to further evaluate the changes include ultrasound or CT of the thorax.

Summary of Overall Candidate Performance
The candidates that were most successful on this case were methodical in their evaluation and were careful to evaluate the entire radiograph. Unsuccessful candidates failed to identify the tracheal nodules as well as the mediastinal shift and thus did not consider atelectasis as a cause for the lung opacity. Also, candidates that were unsuccessful thought that the opacity in the caudal thorax was fat opacity on the lateral views and failed to recognize that the opacity was a combination of the soft tissue and air filled lung summated together on the lateral images. The opacity is quite clearly soft tissue opacity on the VD view.