Abstract
A 15‐month‐old female mixed breed dog was referred with a 3‐day history of progressive dyspnoea and change in bark. Thoracic radiography showed pneumothorax, pneumomediastinum and atelectatic caudal lung lobes. Despite repeated thoracentesis and thoracostomy tube drainage, dyspnoea and cyanosis relapsed leading to the diagnosis of tension pneumothorax. An emergency exploratory thoracotomy showed a perforation on the ventral aspect of the right caudal lung lobe associated with a grass awn. Partial lobectomy was performed, followed by routine thoracotomy closure. The dog had an uneventful recovery and, on re‐examination 2 and 6 months later, was normal.