Presentation
Presented with weight loss, lethargy, and anorexia.
Patient Data
The cardiac silhouette is mildly enlarged, and the pulmonary vessels appear normal. There is a diffuse nodular interstitial pulmonary pattern throughout the lungs. The lungs are mildly hyperinflated. Within the portion of the abdomen included, there is poor serosal detail. There are small gas bubbles present in the cranial thoracic esophagus. The animal is in thin body condition.
Impression: Granulomatous pulmonary infiltrates, consistent with feline infectious peritonitis. Poor detail may be from effusion secondary to FIP, as well as thin body condition.
The tissue sample demonstrates multiple areas of inflammation characterized by histiocytes and neutrophils throughout the lung tissue, accompanied by fibrotic changes, proliferation of type 2 pneumocytes, and blood vessel inflammation. One section reveals inflammatory nodules together with histiocytic infiltration, pleural fibrosis, and increased mesothelial cells. Immunohistochemical testing for feline coronavirus showed cells with positive brown immunoreactivity.
Case Discussion
Abdominal ultrasound showed mild peritoneal effusion and lymphadenopathy. Feline infectious peritonitis was diagnosed on postmortem examination.
Differential diagnoses for the pulmonary pattern and mild pleural effusion include inflammatory granulomatous disease such as FIP or fungal pneumonia, or less likely neoplasia. The poor serosal detail is likely due to a combination of lack of fat and peritoneal effusion. Abdominal ultrasound is recommended to investigate the abdomen.
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