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  1. Problem. A pneumoperitoneum (an abnormal collection of air in the peritoneal cavity) is seen on an abdominal radiograph. The air can be secondary to perforation of the gastrointestinal (GI) tract (most common), from the respiratory tract, or secondary to iatrogenic causes (uncommon).

  2. Immediate questions

      1. Are signs or symptoms of pneumoperitoneum present? These findings can include abdominal distention, respiratory distress, deteriorating blood gas levels, and a decrease in blood pressure.

      1. Were signs or symptoms of necrotizing enterocolitis (NEC) present before? If so, the pneumoperitoneum is most likely to be associated with GI tract perforation.

      1. Are any signs of air leak present? If a pneumomediastinum, pulmonary interstitial emphysema, or pneumothorax is present, the peritoneal air collection is more likely to be of respiratory tract origin.

      1. Is mechanical ventilation being given? High peak inspiratory pressures (PIPs) > a mean of 34 cm H2O can be associated with a pneumoperitoneum.

      1. Did the infant recently undergo abdominal surgery or an invasive procedure such as paracentesis? Intra-abdominal air is normal in the immediate postoperative period and usually resolves without treatment. Paracentesis can perforate a hollow organ.

  3. Differential diagnosis. Pneumoperitoneum develops secondary to perforation of the GI tract, from an air leak from the chest, or postoperatively. In a neonate, unless the infant is on high ventilator settings and has air leak syndrome, the cause is GI perforation until proven otherwise. Identification of the cause directs treatment.

      1. Pneumoperitoneum associated with GI perforation

          1. Spontaneous perforation (no underlying disease process or cause is present) occurs most commonly in the stomach of a full-term neonate. In a preterm infant, the most common site is the jejunoileal area. However, isolated perforation can also occur elsewhere in the intestine of a term infant including the appendix and Meckel diverticulum. Isolated rupture at any level of the GI tract is associated with oral or intravenous indomethacin. A meta-analysis of the effect of early treatment (<96 h) with high doses of steroids for chronic lung disease showed an increased risk of spontaneous GI perforation. An embolic phenomenon secondary to an umbilical artery catheter can also contribute to perforation. Ischemic necrosis secondary to asphyxia or shock may be another cause in the perinatal period.

          1. Secondary perforations (underlying disease process is present). This group consists of GI perforations caused by an underlying disease process.

              1. NEC is the most common cause of secondary perforation. Data show varying results as to whether indomethacin for intraventricular hemorrhage prophylaxis increases spontaneous perforation and perforation with NEC.

              1. Other causes. Malrotation with volvulus (rare), meconium ileus, Hirschsprung disease, bowel atresia, omphalocele, ruptured appendix, mesenteric thrombosis, imperforate anus, strangulated hernia, malrotation with midgut volvulus, gastric and duodenal ulcer perforation, peptic ulcer disease complication, Meckel diverticulum, idiopathic gastric necrosis, and pneumatosis cystoides intestinalis.

          1. Traumatic perforations. An iatrogenic pneumoperitoneum caused by an intervention by a health-care professional.

              1. Neonatal rectal perforations. These can be caused by a rectal thermometer or rectal tubes. Because of the shape of the neonatal rectum, when a rectal thermometer is placed to a depth of 2 cm, it impinges on the anterior wall. Any attempt to push it any further may result in perforation. Use of axillary thermometers eliminates this risk totally.

              1. Nasogastric tube trauma during placement can cause perforation and pneumoperitoneum.

              1. Intubation trauma. During an intubation attempt, the endotracheal tube can be inadvertently ...

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