Migration of an accessory spleen secondary to chronic diaphragmatic hernia in a cat

A 4‐year‐8‐month‐old, neutered, male, domestic shorthair cat was presented with paradoxical breathing, tachypnoea and abdominal distension. Ultrasound suggested possible pyothorax and yielded only a small sample. Computed tomography confirmed a diaphragmatic hernia with herniation of an accessory spleen and omentum into the thorax. Surgical correction was performed, including removal of the herniated tissue, which cultured Escherichia coli and Prevotella species. The cat initially recovered well. Fourteen weeks later, mild respiratory effort recurred, requiring thoracocentesis. At 16 weeks, the cat presented with marked respiratory distress. Radiographs revealed a ventral thoracic opacity, suspected to represent pyothorax relapse, whereas the diaphragmatic silhouette was intact. Due to recurrent thoracic complications and poor long‐term prognosis, compassionate euthanasia was elected.