Necrotizing Enterocolitis - Causes, Symptoms and Treatment

Neonatal necrotizing enterocolitis (NE) is a clinical condition characterized by an initial mucosal intestinal injury that may progress to transmural bowel necrosis. Although NEC occurs frequently, its cause is unknown. NEC is the single most frequent surgical emergency in neonates in North America. With early detection, the survival rate is 60% to 80%. Infectious complications associated with bowel necrosis include bacterial peritonitis, systemic sepsis, and intra-abdominal abscess formation.

Causes of Necrotizing Enterocolitis

NEC occurs most often in premature infants (less than 34 weeks' gestation) and those of low birth weight (less than 5 lb [2.3 kg]). However, one in ten infants who develop NEC is full-term. NEC is occurring more frequently, possibly because of the higher incidence and survival of premature and low-birth-weight infants. More than 90% of NEC cases occur after initiation of feedings. Among premature and low-birth-weight infants in intensive care nurseries, incidence varies from 1 % to 12%. NEC is associated with 2% of all infant deaths.

The exact cause of NEC is unknown. Suggested predisposing factors include birth asphyxia, postnatal hypotension, respiratory failure, hypothermia, sepsis, acidosis, and structural cardiac defects, as well as pharmacological associations, such as cocaine exposure and indomethacin treatment. NEC may al so be a response to significant prenatal stress, such as premature rupture of membranes, placenta previa, maternal sepsis, toxemia of pregnancy, or breech or cesarean birth.

According to a current theory, NEC develops when the infant 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 immunologic activity and because it contributes to the production of hydrogen gas.

Signs and Symptoms of Necrotizing Enterocolitis

Any neonate who has suffered from perinatal hypoxemia has the potential for developing NEC. A distended (especially tensc 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. Other clinical features are increasing residual gastric contents (which may contain bile), bilious vomitus, and occult or gross blood in stools. One-fourth of patients have bloody diarrhea. A red or shiny, taut abdomen may indicate peritonitis. Nonspecific signs and symptoms include thermal instability, lethargy, metabolic acidosis, jaundice, and disseminated intravascular coagulation (DIC). The major complication is perforation, which requires surgery. Recurrence of NEC and mechanical and functional abnormalities of the intestine, especially stricture, are the usual cause of residual intestinal malfunction in any infant who survives acute NEC, and may develop as late as 3 months postoperatively.

Diagnosis for Necrotizing Enterocolitis

Successful treatment of NEC relics on early recognition based on the following diagnostic test results:

1.Anteroposterior and latcral abdominal X-rays confirm the diagnosis by showing nonspecific intestinal dilation and, in later stages of NEC, pneumatosis cystoides intestinalis (gas or air in the intestinal wall). Portal vein gas and fixed or thickened small bowel loops are also important radiographic findings. Sequential screening films are taken every 6 to 8 hours during the early disease stages.

2.Platelet count may fall below 50,000/ul..

3.Serum sodium levels are decreased.

4.Arterial blood gas (ABG) levels show metabolic acidosis (a result of sepsis).

5.Bilirubin levels show infection-induced breakdown of red blood cells.

6.Blood and stool cultures identify the infecting organism.

7.Guaiac test detects occult blood in stools.

Treatment for Necrotizing Enterocolitis

Up to 90% of infants with NEC can be managed without surgery. The first signs of NEC necessitate discontinuation of oral intake to rest the injured bowel. l.V. fluids, including hyperalimentation, maintain fluid and electrolyte balance and nutrition during this time; passage of a nasogastric (NG) tube allows bowel decompression. Correction of hypoxemia, hypotension, acidosis, and any other reversible medical problems is needed. Optimizing cardiac performance is necessary. Serial physical examinations, platelet counts, lactate levels, and ABGs are the most useful indications of progressive sepsis. Drug therapy consists of parenteral administration of broad-spectrum antibiotics to suppress bacterial flora and prevent bowel perforation. (These drugs can also be administered through an NG tube if necessary.)

Special Considerations and Prevention Tips for Necrotizing Enterocolitis

• To help prevent NEC, encourage mothers to breast-feed because breast milk contains macrophages that fight infection and has a low pH that inhibits the growth of many microbes.
• As the bowel swells and breaks down, gas-forming bacteria invade damaged areas, producing free air in the intestinal wall. This may result in fatal perforation and peritonitis.
• Be alert for signs of gastric distention and perforation.
• Do not take any rectal temperatures, to avoid perforating the bowel.
• Prevent cross-contamination by disposing of soiled diapers properly and washing hands after diaper changes.
• Prepare the parents for a potential deterioration in their infant's condition. Explain all treatments, including why feedings are withheld.
• After surgery, the infant needs mechanical ventilation. Gently suction secretions and monitor respirations often.
• Replace fluids lost through NG tube and stoma drainage. lnclude drainage losses in output records. Weigh the infant daily. A daily weight gain of 0.35 to 0.7 oz (10 to 20 g) indicates a good response to therapy.
• An infant with a temporary colostomy or ileostomy should be referred to an en terostomal therapy nurse to assist the patient and family in meeting needs.
• Encourage the parents to participate in their infant's physical care after his condition is no longer critical.
• Because of the infant's small abdomen, the suture line is near the stoma. Maintaining a clean suture line may be problematic. Good skin care is essential because the immature infant's skin is fragile and vulnerable to excoriation and the active enzymes in bowel secretions, which are corrosive.
• Improvise infant-sized colostomy bags from urine collection bags, medicine cups, or condoms. Karaya gum is helpful in making a seal.
• Watch for wound disruption, infection, dehiscence, and excoriation - potential dangers because of severe catabolism.
• Watch for intestinal malfunction from stricture or short-bowel syndrome. Such complications usually develop 1 month after the infant resumes normal feedings.
• Encourage parental visits.
• Instruct mothers that they may refrigerate their milk for 48 hours but shouldn't freeze or heat it because this destroys antibodies. Tell them to use plastic-not glass-containers because leukocytes adhere to glass.
• Breast-feeding mothers should pump milk while the baby is not taking anything by mouth, in order to maintain an adequate milk supply.