Recurrent pyothorax in the cat: mediastinal abscess on CT
Adult domestic shorthair cat with pyothorax that recurs despite chest drainage and appropriate antibiotics. Contrast-enhanced thoracic CT, transverse image:
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The caudal mediastinal lesion (blue arrow) has fluid attenuation and a strongly enhancing wall; the red arrow marks the displaced oesophagus. What is the most likely interpretation?
chevron_right Show answer and explanation
A. Fluid-filled oesophageal diverticulum
A diverticulum communicates with the oesophageal lumen and usually contains food or gas; it lacks a thick, strongly enhancing wall and does not explain the pyothorax.
B. Incidental benign mediastinal cyst
Mediastinal cysts have a thin wall without marked enhancement, are usually incidental and lie in the cranial mediastinum. They do not sustain a pyothorax.
C. Paraoesophageal mediastinal abscess
Correct. A fluid-filled lesion with peripheral ring enhancement is typical of an abscess. It is a persistent focus that explains the recurrence and usually needs surgical management (thoracoscopy or thoracotomy).
D. Mediastinal lymphoma with central necrosis
Feline mediastinal lymphoma is usually a solid cranial mediastinal mass with more homogeneous enhancement. It does not fit a recurrent pyothorax.
lightbulb Key takeaway
If pyothorax recurs despite proper drainage and antibiotics, use CT to look for a persistent focus: abscess, foreign body or affected lung lobe. A fluid lesion with ring enhancement is typical of an abscess and usually needs surgery to resolve the problem.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.