4 year old male neutered Labrador Retriever. Heat stroke and pneumonia diagnosed 1 week ago.

Allison Zwingenberger

University of California, Davis

Publication Date: 2011-10-14

Patient

History

4 year old male neutered Labrador Retriever. Heat stroke and pneumonia diagnosed 1 week ago.

Respiratory distress and pyothorax with pneumothorax diagnosed yesterday.

Findings

Radiographs: This is an after-hours study consisting of multiple thoracic projections before and after chest tube placement. On the initial studies today, there is a moderate amount of gas within the pleural cavities bilaterally. There is lung lobe retraction away from the body wall. there is thickened pleura. There are persistent alveolar infiltrates with air bronchogram formation within the right middle lung lobe. In addition there are unusual rounded gas opacities in this lung lobe. Bilateral chest tubes were then placed. Later projections document almost complete resolution of the bilateral pneumothorax. The chest tubes terminated within the cranioventral thorax. There are persistent alveolar infiltrates with air bronchogram formation within the right middle lung lobe. The unusual gas opacities also persist within this lung lobe as well. The cardiovascular structures are within normal limits.

CT: Minimal pleural air is identified surrounding the chest tubes bilaterally. There is increase in soft tissue opacity and consolidation in the ventral portion of the right middle lung lobe, with multifocal regions of gas trapping, the largest measuring 1 cm in diameter. There are mild increased infiltrates and soft tissue opacity in the ventral aspect of the left cranial lung lobe, adjacent to the chest tube. Thickened irregular pleura with a semicircular region of soft tissue is present on the dorsal aspect of the left caudal lung lobe.

DDx

• Bilateral moderate pneumothorax with successful resolution via chest tube placement.
• Persistent alveolar infiltrates within the right middle lung lobe as well with unusual gas opacities which are consistent with abscessation either secondary to aspiration pneumonia or infarction due to the heat stroke.

Diagnosis

CT: Right middle lung lobe pneumonia with abscessation, which is likely the source of the patient’s pneumothorax. An underlying foreign body is not identified, but cannot be ruled out. Additional abnormalities on the left side, suggestive of pneumonia and pleuritis, but underlying atelectasis may be component, especially ventrally.

Pathology Lung: Examined are two similarly affected sections of lung in which the normal architecture is effaced and a central irregular cavitation is lined with amorphous pale eosinophilic debris (necrosis) surrounded by variably defined layers of densely cellular mixed inflammatory infiltrate, and variably mild to moderate fibroconnective tissue. The inflammatory infiltrate is composed of abundant numbers of variably degenerate neutrophils, histiocytes, lymphocytes, plasma cells, and occasional multinucleated giant cells. The surrounding fibroconnective tissue is composed of occasional, variably sized collagen bundles and fibroblasts with plump oval to pyriform nuclei and eccentric cytoplasmic tails are scattered throughout the examined sections. Subjacent to the cavitation, are multiple confluent regions of necrosis admixed with a densely cellular inflammatory infiltrate similar to that previously described. A mild basophilic (mucoid) exudate is present within several bronchioles and bronchi and is occasional mixed with a mild mixed inflammatory cells.

Pathology comment: The lesions are consistent with the clinical diagnosis of a ruptured abscess. Interestingly, this abscess had a well-defined draining tract suggestive of a foreign body reaction, such as that seen with a migrating grass awn, however no phytogenous material was identified in the lesion.