Necrotizing enterocolitis
LIFE-THREATENING DISORDERNeonatal necrotizing enterocolitis (NEC) is a clinical condition characterized by an initial mucosal intestinal injury that may progress to transmural bowel necrosis. Although NEC is common, its cause is unknown. NEC is the leading surgical emergency in neonates in North America.
Infectious complications associated with bowel necrosis include bacterial peritonitis, systemic sepsis, and intra-abdominal abscess formation.
Causes
NEC usually occurs in premature neonates (less than 34 weeks’ gestation) and those of low birth weight (less than 5 lb [2.3 kg]). NEC is occurring in more neonates, possibly because of the higher incidence and survival of premature and low-birth-weight neonates.
Clinical TipMore than 90% of NEC cases occur after initiation of feedings.
Possible risk factors
The exact cause of NEC is unknown. Suggested predisposing factors include premature birth and small size for gestational age; blood exchange transfusions; feeding of concentrated formulas; infectious causes; respiratory failure; hypothermia; sepsis; acidosis; and structural cardiac defects as well as pharmacologic associations, such as cocaine exposure and indomethacin treatment.
NEC may also be a response to significant prenatal stress.
Causative theory
NEC can develop when the infant suffers perinatal hypoxemia due to shunting of blood from the gut to more vital organs. Subsequent mucosal ischemia provides an ideal medium for bacterial growth. Hypertonic formula may increase bacterial activity because—unlike maternal breast milk—it doesn’t provide protective immunity and because it contributes to the production
of hydrogen gas. As the bowel swells and its integrity breaks down, gas-forming bacteria invade damaged areas, producing free air in the intestinal wall. This may result in fatal perforation and peritonitis.
of hydrogen gas. As the bowel swells and its integrity breaks down, gas-forming bacteria invade damaged areas, producing free air in the intestinal wall. This may result in fatal perforation and peritonitis.
Signs and symptoms
Any infant who has suffered from perinatal hypoxemia has the potential for developing NEC. A distended (especially tense or rigid) abdomen, with gastric retention, is the earliest and most common sign of oncoming NEC, usually appearing from 1 to 10 days after birth.
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