Abdominal air pockets. X-ray showing air in the abdomen, dark masses below the heart, a condition known as pneumoperitoneum. The white bands in upper frame are the ribs, which encase the lungs (dark). The white mass in the centre is the heart. The air pockets are trapped below the diaphragm. The most common causes of pneumoperitoneum are gas escaping from a perforated bowel and suction of air through the female genital tract. Pneumoperitoneum is treated by removal of the air and repair of the underlying problem.