Postoperative chylothorax following surgical transection of a left ligamentum arteriosum in a cat with a persistent right aortic arch

A 6‐month‐old intact female domestic shorthair cat was presented for surgical correction of a vascular ring anomaly. The main clinical sign on presentation was persistent regurgitation after ingestion of solid food. Computed tomography of the thorax confirmed the diagnosis of a persistent right aortic arch (PRAA) with a left ligamentum arteriosum. The left ligamentum arteriosum was identified, ligated and transected via a left fifth intercostal thoracotomy to relieve the oesophageal constriction associated with the persistent right aortic arch. Within 24 h postoperatively, the patient developed dyspnoea and tachypnoea. A pleural effusion was noted on drainage of the left thoracic drain, which had been placed intraoperatively. The pleural effusion analysis was consistent with a chylothorax. A right‐sided thoracostomy tube was placed in addition to the left, and a continuous drainage system was utilised. The chylous effusion resolved on Day 6 postoperatively. This case report highlights the occurrence and management of iatrogenic chylothorax following surgical correction of a PRAA with a left ligamentum arteriosum in a cat.