Caval foramen hernia in a cat

CASE SUMMARY: A 3-year-old neutered female domestic shorthair cat presented for a 2-week history of hyporexia, lethargy and weight loss. Aspartate aminotransferase, alanine aminotransferase and cholesterol were mildly elevated. Thoracic radiographs identified a lobulated soft tissue opacity in the caudal thorax to the right of midline, with the border effacing the caudal vena cava and broad-based towards the diaphragm. The broad base was suggestive of diaphragmatic hernia, with the other radiographic features and location suggestive of caval foramen hernia. Ultrasound confirmed diaphragmatic hernia with liver herniation. CT showed the herniation of multiple liver lobes and the gallbladder through a defect at the caval foramen. Herniorrhaphy was performed via ventral midline coeliotomy. Following this procedure, the cat’s clinical signs resolved and its weight has been regained. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first report of successful caval foramen herniorrhaphy in a cat. Caval foramen hernia is a type of congenital diaphragmatic hernia. The authors suggest that its embryopathology involves defective septum transversum development. The case was detected during the standard diagnostic investigation of non-specific clinical signs. Its radiographic findings may easily be mistaken for a pulmonary mass. Although not seen in our case, caval foramen hernia is commonly associated with caudal vena cava obstruction, which can potentially result in Budd–Chiari-like syndrome.