Necrotizing Enterocolitis

Necrotizing enterocolitis is characterized by diffuse or patchy intestinal necrosis. It's accompanied by sepsis in about one-third of cases. Sepsis usually involves Escherichia coli, Clostridium, Salmonella, Pseudomonas, or Klebsiella. Initially, necrosis is localized, occurring anywhere along the intestine, but most often it's right-sided (in the ileum, ascending colon, or rectosigmoid). With early detection, the survival rate is 60% to 80%. If diffuse bleeding occurs, the disorder usually results in disseminated intravascular coagulation.

Necrotizing enterocolitis is most common in premature infants (less than 34 weeks' gestation) and those of low birth weight (less than 5 lb [2.3 kg]). It's related to 2% of all infant deaths, with onset usually occurring 1 to 14 days after birth.

Necrotizing enterocolitis has become more prevalent in some areas, possibly because of the higher incidence and survival of premature infants and neonates who have low birth weights. One in 10 infants who develops this disorder is full-term.

Causes

It is thought that the intestinal tissues are somehow weakened by too little oxygen or blood flow. When feedings are started and the food moves into the weakened area of the intestinal tract, bacteria from the food can damage the intestinal tissues. The tissues may be severely damaged and die, which can cause a hole to develop in the intestine. This can lead to severe infection in the abdomen.

Signs and Symptoms

The maternal and patient histories may reveal one or more predisposing factors. Just before the onset of necrotizing enterocolitis, the infant may experience temperature instability, bradycardia, apnea, and lethargy or irritability. You may notice an increase in gastric aspirates, bile-stained vomitus, or bloody diarrhea. On inspection, the abdomen may appear distended. Suspect gastric retention if the abdomen feels tense or rigid on palpation. A taut abdomen, with red or shiny skin, may indicate peritonitis.

Diagnostic tests

Stool cultures may be used to identify the infecting organism, and stool analysis to identify occult blood.

Anteroposterior and lateral abdominal X-rays are used to confirm the diagnosis. These X-rays show nonspecific intestinal dilation and, in later stages of necrotizing enterocolitis, pneumatosis cystoides intestinalis (gas or air in the intestinal wall).

Blood studies show several abnormalities. Platelet count may fall below 50,000/µl, and serum sodium levels are decreased. Arterial blood gas levels show metabolic acidosis, indicating sepsis. Bilirubin levels are elevated because of infection-induced breakdown of erythrocytes. Blood cultures are used to identify the infecting organism. Clotting studies and hemoglobip levels show disseminated intravascular coagulation.

Abdominal X-rays are used to monitor the progress of the disorder.

Treatment

Medical management is supportive, with successful treatment dependent on early detection. At the first signs of necrotizing enterocolitis, oral feedings are discontinued for about 7 to 10 days to rest the injured bowel. l.V. fluids, including total parenteral nutrition, maintain fluid and electrolyte balance and nutrition during this time. To aid bowel decompression, a nasogastric (NG) tube is placed and connected to suction. If coagulation studies indicate a need for transfusion, the infant usually receives dextran to promote hemodilution, increase mesenteric blood flow, and reduce platelet aggregation.

Antibiotic therapy consists of parenteral administration of an aminoglycoside or ampicillin to suppress bacterial flora and prevent bowel perforation. (These drugs can also be administered through an NG tube, if necessary.)

Surgery is indicated if the patient develops any of the following: signs of perforation (free intraperitoneal air on X-ray or symptoms of peritonitis), respiratory insufficiency (caused by severe abdominal distention), progressive and intractable acidosis, or disseminated intravascular coagulation.

Surgery is used to remove all necrotic and acutely inflamed bowel, then creates a temporary colostomy or ileostomy. The procedure must leave at least 12" (30 cm) of bowel, or the infant may suffer from malabsorption or chronic vitamin B12 deficiency.

Prevention of necrotizing enterocolitis:

Because the exact causes of NEC are unclear, prevention is often difficult. Studies have found that breast milk may reduce the incidence of NEC. Also, starting feedings after a baby is stable and slowly increasing feeding amounts have been recommended.