Diaphragmatic hernias are becoming increasingly common due to radiofrequency ablation of malignant liver tumors. Most patients eventually present with symptoms caused by bowel obstruction. A 54-year-old woman with pleuritic pain and fever had a right-sided enterothorax probably caused by hemihepatectomy several years before. The patient was diagnosed with perforated gangrenous intrathoracic appendicitis during an emergency laparotomy for suspected incarceration of her diaphragmatic hernia. She was treated with an appendectomy and suturing of her right hemidiaphragm. An acquired diaphragmatic hernia should therefore be surgically repaired as soon as it is diagnosed in order to avoid complications.