Necrotizing enterocolitis : imaging and risk assessment

Despite decades of research on necrotizing enterocolitis (NEC), no major finding has improved the mortality and morbidity of the disease or changed the clinical management. The exact pathogenesis remains unclear, but several factors such as immature intestinal immunity, impaired bowel microcirculation, enteral nutrition and abnormal microbiota may play important roles. In the post-surfactant era, the NEC patient population has changed, with an increasing proportion of extremely preterm infants. Plain abdominal radiography is still considered the gold standard imaging technique for NEC. Unfortunately, abdominal radiography has low sensitivity and specificity, making the decision to intervene surgically very challenging. Recent studies have shown the increasing role of abdominal ultrasound and near-infrared spectroscopy in the diagnosis and monitoring of NEC. The overall aim of this project was to describe the preterm infants at risk of NEC and how those who develop severe NEC and need surgical treatment could be identified early, using new imaging techniques and monitoring. The aim of Paper I was to describe the difference in the clinical and radiological presentation of NEC in extremely preterm infants compared with more mature ones. Extremely preterm infants show less typical signs of NEC, such as bloody stool or pneumatosis intestinalis, compared with more mature neonates. The aim of Paper II was to assess if splanchnic oxygenation, as measured by near infrared spectroscopy (NIRS), in the first week of life is associated with the risk of developing necrotizing enterocolitis. Extremely preterm infants underwent NIRS monitoring during enteral nutrition. Low mean splanchnic oxygenation, below 30%, was associated with an increased risk of developing necrotizing enterocolitis during enteral nutrition in the first days of life. The aim of Paper III was to determine whether a correlation exists between the sonographic findings and the clinical outcomes, defined as surgery or death in infants with NEC. Infants with a confirmed diagnosis of NEC, who underwent an abdominal ultrasound, were included in the study. The sonographic sign of complex fluid collections appeared to be strongly correlated with the need for surgery in infants with severe NEC. The aim of Paper IV was to assess if hyponatremia, or worsening of already present hyponatremia, at the onset of necrotizing enterocolitis is associated with intestinal inflammation and ischaemia requiring surgery or death. In this cohort study, neonates with a confirmed diagnosis of NEC were included. Hyponatremia and a sudden decrease in plasma sodium concentration at the onset of NEC can be useful markers for severe intestinal inflammation/ischemia where an imminent need for surgery can be expected