Necrotizing enterocolitis (NEC), the most common infantile gastrointestinal emergency, is one of the most challenging conditions encountered by pediatric surgeons. It occurs in up to 3 in every 1000 live births, and manifests as intestinal ischemia and inflammation.
While the exact cause is unknown, there is a strong predominance among premature babies and those who are formula-fed. Infants at risk include those below 1000 g weight at birth, those with low Apgar scores, and those with cardiac or gastrointestinal abnormalities. Maternal risk factors include the use of cocaine, infections, and hypertension during gestation.
The integrity of the bowel wall in NEC is compromised, which leads to bacteria entering the abdomen causing a massively and rapidly extending infection. Infants with NEC typically present within the first two weeks after birth with abdominal swelling or bloating, and discoloration of the abdominal wall, along with poor feeding tolerance.
These infants may experience vomiting that is green in color, and may have bloody stools and fever. Furthermore, they may appear sluggish and tired with a lack of energy. They often experience problems with breathing, including apnea. Cases that are not recognized in time may develop fatal shock.
Diagnosis is based on the presence of the classical signs and symptoms of NEC, along with the confirmatory findings of abdominal radiography, which is the mainstay of the clinical workup. Ultrasound may also be used for diagnostic purposes. Abdominal X-rays confirm NEC by revealing the presence of gas in the bowel wall and/ or cavity secondary to perforation.
The abdominal radiographs show asymmetrical dilated bowel loops and intramural gas, also known as pneumatosis intestinalis, in many cases. Portal venous gas may also be seen. Bowel wall edema with prominence of the haustrations, leading to thumbprinting, is another feature. If there is perforation of the bowel wall (pneumoperitoneum), bowel wall air is seen on both sides of the intestinal wall. This is called the Rigler sign. There is also a ‘football sign’ that occurs when the falciform ligament being outlined by air in the peritoneal cavity. However, this finding of free gas in the bowel is visible in only half to 75% of patients with perforation.
Ultrasound may show thickening of the bowel wall and changes to the vasculature. The vasculature is hypervascular in the early stage of NEC, but it soon becomes hypovascular in the later stage. Furthermore, intramural gas is visualized as hyperechoic. In the presence of bowel perforation, free fluid containing echogenic material is present.
Owing to the quickly progressive and life-threatening nature of NEC, prompt identification and aggressive treatment are crucial to ensuring a favorable clinical outcome. The condition is managed with both medical and surgical therapy. Candidates for medical therapy are usually in stages 1 or II of the condition, corresponding to mild and/or moderate NEC. In comparison, stage III patients are in shock and/or have bowel perforation. Stage III patients are treated surgically.
Cessation of oral feeding in combination with broad-spectrum antibiotics and gastric aspiration, as well as other supportive measures, is the crux of medical management. Patients with bowel perforation usually require resection of all necrotic bowel tissue with the subsequent creation of a proximal enterostomy. Following treatment, complications such as malabsorption and intestinal scarring may arise.