A young adult presented with signs of peritonitis following tube thoracostomy for suspected acute hydropneumothorax. Attempted decompression of the chest by tube thoracostomy had caused gastric perforation, and on surgical exploration, he was found to have a congenital diaphragmatic hernia with herniation of the stomach, spleen and colon. All intensive care doctors and emergency room physicians dealing with the care of patients with acute respiratory failure should be taught to recognize and keep the possibility of a Bochdalek hernia in mind, especially in young adults presenting with unusual respiratory and gastrointestinal symptoms.