Necrotizing Enterocolitis

. Necrotizing enterocolitis (NEC) is an acquired gastrointestinal disease process that is a major problem in preterm infants. The incidence is 1% to 5% of admissions to the neonatal intensive care unit. Al­though approximately 90% of infants affected are pre­term infants weighing less than 1500 g, 10% of infants affected are term infants. The mortality rate varies from 20% to 40%.

The exact cause of NEC is unknown, but it is thought to be multifactorial. Risk factors for NEC include birth as­phyxia, umbilical artery catheterization, patent ductus ar-teriosus, polycythemia, enteral feeding, and medications such as indomethacin, vitamin E, and xanthines.²² There is agreement that the process begins with diminished per-fusion of the intestinal wall, which results in ischemia and hypoxia that leads to necrosis and gangrene. Although bacterial infection plays a role in the disease, it is not thought to be the initiating event. Milk feeding has been implicated. Approximately 93% of infants in whom NEC develops have been fed enterally.²³ Human milk and com­mercial formulas serve as substrates for bacterial growth in the gut.

The ileum is most commonly affected, followed by the ascending colon, cecum, transverse colon, and recto-sigmoid. The necrosis of the intestine may be superficial, affecting only the mucosa or submucosa, or it may extend through the entire intestinal wall. Perforation can occur and lead to peritonitis.²²,²⁴ The manifestations of NEC are variable, but the usual presentation includes abdominal dis-tention, gastric aspirates, bilious stools, lethargy, apnea, and hypoperfusion. The infant often appears septic. Laboratory examination may reveal leukocytosis or leukopenia, neu-tropenia, thrombocytopenia, glucose instability, electrolyte imbalance, metabolic acidosis, hypoxia, hypercapnia, and disseminated intravascular coagulation. Blood cultures are positive for only approximately 30% of these patients. Microorganisms reported in NEC include Escherichia coli, Clostridium difficile, Clostridium perfringens, and Klebsiella, Enterobacter, Pseudomonas, and Salmonella species.²²

Clinical diagnosis is primarily radiographic. The radio-graphic hallmark of NEC is pneumatosis intestinalis or intramural air. Pneumoperitoneum is indicative of intesti­nal perforation. A large, stationary, distended loop of in-testine on repeated radiographs may indicate gangrene, and a gasless abdomen may indicate peritonitis.²²

Treatment includes cessation of feedings, stomach de­compression, broad-spectrum antibiotic coverage, and sup­portive treatment. Intestinal perforation requires surgical intervention. Intestinal resection of dead intestine with a diverting ostomy is the procedure of choice.²²