EXPRESS: Video-assisted thoracic surgery of a caudal mediastinal paraoesophageal abscess in a cat with recurrent pyothorax

Case summary A 6-year-old spayed female domestic shorthair cat was presented with acute respiratory distress and lethargy. Three months prior, the cat had been medically managed for a bacterial pyothorax. Initial stabilisation included oxygen supplementation, and a point-of-care ultrasound revealed bilateral pleural effusion. A thoracostomy tube was placed and pleural fluid was aseptically collected. Cytological evaluation of the pleural fluid was consistent with a septic neutrophilic exudate, with Fusobacterium russii , Bacteriodes pyogenes and Porphyromonas gingivalis isolated on anaerobic bacterial culture. Computed tomography scan of the thorax revealed a caudal mediastinal paraoesophageal mass, with no gross mucosal abnormalities or foreign material apparent on oesophagoscopy. Lack of response to medical management promoted video-assisted thoracic surgery (VATS), with partial conversion to a thoracoscopic-assisted approach to improve visualisation. Histopathology of the mass was consistent with an abscess, and Fusobacterium russii and Bacteriodes pyogenes were isolated. No primary cause for the caudal mediastinal paraoesophageal abscess (CMPA) was identified. The cat was discharged with metronidazole following thoracostomy tube removal four days postoperatively. There was no recurrence of clinical signs and pleural effusion on point-of-care ultrasound at three months follow-up. Relevance and novel information CMPAs are rarely described in cats. This case outlines the clinical features, diagnostic investigations, treatment and outcome of a cat with a CMPA. The case reinforces the importance of repeat diagnostic imaging in cats with recurrent pyothorax and highlights the feasibility and challenges of VATS for CMPA removal, which has not been previously described in cats.