Necrotizing Enterocolitis (NEC) Overview

Necrotizing enterocolitis (NEC) is a life-threatening condition that manifests as inflammation of the intestines. This devastating disease affects mostly premature babies, who account for up to 8 out of every 10 cases. In NEC, bacteria invade the intestinal wall. The resulting local infection and inflammation lead to the destruction of the intestinal lining, even through its entire thickness.

A breach in the integrity of the bowel wall enables bacteria to escape into the abdominal cavity. By this means, the bacteria cause a massive infection, which has the ability to progress quickly and may lead to death if not treated immediately. Hence, NEC is a medical emergency.

Patients typically present with swelling or bloating, and poor feeding tolerance. Moreover, they may experience vomiting, blood in the stool, lethargy, apnea and fever. These signs and symptoms usually develop within the first 2 weeks of life. Diagnosis is made with the help of physical examination and abdominal X-rays, which typically show the presence of air in the abdominal cavity. Treatment may vary depending on the disease extent and the overall health of the infant, but includes antibiotic therapy, intravenous feeding, and in serious cases, ventilator support and surgery.

Epidemiology

In the United States, the incidence of NEC ranges between 0.3 – 2.4 per 1000 live births. This frequency is suggested to be similar in other countries, but may be lower in countries with lower rates of premature births. The prevalence of NEC is equal in male and female infants, and the incidence is inversely proportional to the gestational age and birth weight. The highest rates of NEC are seen in infants with a birth weight less than 1 kg. Infants born with a weight between 1.5 – 2.5 kg and those who are born after 36 weeks of gestation have significantly lower chances of developing NEC.

Risk factors

There have been studies conducted to determine the susceptibility patterns of neonates. While small preterm babies continue to have the highest risk, these studies show that a different pattern operates in late preterm babies (born after the 35th week of gestation). These infants are more likely to develop NEC if they had a low Apgar score and difficulties, such as asphyxia at birth and sepsis.

These babies are at a particularly increased risk if they have congenital cardiac or gastrointestinal defects that may cause ischemia of the mesentery. Other risk factors, such as gestational diabetes and intrauterine growth retardation, increase the chances of late preterm babies developing NEC.    

Some studies have hypothesized that prenatal factors may also be involved, especially those that may lead to the damage of the intestinal mucosa and vasculature of the unborn child. One such possible risk factor is a pregnant woman who uses cocaine. Although more data is needed to fully elucidate their roles in NEC, it is believed that maternal hypertension, infections, as well as other complications that compromise placental blood flow, may all cause growth-restriction during intrauterine life. Some studies have implicated these factors as potential independent NEC predictors.

Infants who are born with patent ductus arteriosus (PDA) and treated with indomethacin to close the PDA have been shown to be at risk for developing NEC. Studies have shown that the use of ibuprofen in these infants reduces the risk of NEC development. Infants are 6.4 times and 28.6 times more likely to develop NEC if they were not fed with fortified breast milk and if they were under respiratory support, respectively, according to some studies. Furthermore, NEC research shows that more children fed on formula develop NEC than those who are breast fed.