Causes and Symptoms of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common cause of gastrointestinal emergencies in newborns. It is manifested by ischemia and inflammation of the intestinal mucosa.

The condition affects as many as 3 in every 1000 live births, with a predominance in infants born prematurely.

The risk is also increased in infants with a birth weight below 1000 g, those born with low Apgar scores, and/ or cardiac or gastrointestinal anomalies.

Moreover, infants born to mothers who used drugs, particularly cocaine, or mothers who had an infection, hypertension or other complications that comprised placental blood flow, may also be at an increased risk.

Any part of the small intestine or colon may be affected in NEC; however, the terminal ileum and the proximal part of the ascending colon are the most commonly involved bowel segments.

Through destruction of the bowel wall, bacteria gain entry into the abdominal cavity and cause a massive and rapidly progressing infection that is life-threatening.

NEC has been and continues to be one of the more challenging conditions that pediatric surgeons encounter. However, early identification of the disease, with immediate and aggressive treatment, significantly improves the clinical outcome.   

Etiology

The etiology of the condition remains largely uncertain. However, several studies have been conducted and are underway to understand the pathogenesis and pathology of NEC.

It is believed to be multifactorial in origin. Factors such as microbial dysbiosis (imbalance in the intestinal microbiota) and immaturity of the intestines have been considered in the pathogenesis.

An underdeveloped intestinal immune environment in conjunction with a breach in the epithelial barrier or mucosal lining of the bowel can result in inflammation and ensuing sepsis.

Intestinal immaturity, aside from weak immune defenses, also presents with an underdeveloped vascular network that cannot provide adequate perfusion for the tissue.

It has been postulated that compromising the flow of blood and/ or oxygen to the intestines further weakens their integrity. This allows for bacteria, which would otherwise be kept in check, to cause local infection, inflammation and ultimately perforation of the intestinal wall, that leads to severe consequences.

Studies show that the microbial environment of an infant’s intestines is shaped by factors such as natural birth versus Cesarean delivery, antibiotic exposure, and formula feedings.

Despite the many theories that exist and attempts to explain them, a consistent finding is that infants who do develop NEC are more often premature and formula-fed.

Clinical Presentation

An infant with NEC, who is being fed on formula and not breast milk, will typically present within the first two weeks of life with swelling or bloating, along with poor feeding tolerance.

The distended abdomen may be blue or red in color. Parents may note vomiting that is green, blood in the stool and a fever.

The baby will appear sluggish or tired, lethargic, with low energy levels, and may experience breathing problems and a low respiratory rate, or even apnea, as well as a slowed heart rate.

If the condition is not recognized early enough, these infants may go into shock with a precipitous decrease in blood pressure.