Traumatic diaphragmatic hernia in a clinically normal dog.

A 3.5-year-old border collie was presented for routine ovariohysterectomy. A preoperative physical examination revealed no abnormalities, but, under anesthesia, the patient became dyspneic and cyanotic. Plain radiography indicated the presence of a diaphragmatic hernia. The herniated structures were returned to the abdomen and the diaphragmatic defect was surgically repaired.