NECROTIZING ENTEROCOLITIS
Saturday, August 16, 2008
Essentials of Diagnosis & Typical Features
Necrotizing enterocolitis is the most common acquired gastrointestinal emergency in the newborn infant; it most often affects preterm infants, with an incidence of 10% in infants of birth weight less than 1500 g. In term infants, it occurs in association with polycythemia, congenital heart disease, and birth asphyxia. The pathogenesis of the disease is a multifactorial interaction between an immature gastrointestinal tract, mucosal injury, and potentially injurious factors in the lumen. Previous intestinal ischemia, bacterial or viral infection, and immunologic immaturity of the gut are thought to play a role in the genesis of the disorder. In up to 20% of affected infants, the only risk factor is prematurity.
Clinical Findings
The most common presenting sign is abdominal distention. Other signs include vomiting or increased gastric residuals, heme-positive stools, abdominal tenderness, temperature instability, increased apnea and bradycardia, decreased urine output, and poor perfusion. The complete blood count may show an increased white blood cell count with an increased band count or, as the disease progresses, absolute neutropenia. Thrombocytopenia is often observed along with stress-induced hyperglycemia and metabolic acidosis. Diagnosis is confirmed by the presence of pneumatosis intestinalis (air in the bowel wall) on x-ray. There is a spectrum of disease, and milder cases may exhibit only distention of bowel loops with bowel wall edema (thickened-appearing walls on x-ray).
Treatment
A. Medical Treatment: Necrotizing enterocolitis is managed by decompression of the gut by nasogastric tube, maintenance of oxygenation, mechanical ventilation if necessary, and intravenous fluids (colloid and normal saline) to replace third-space gastrointestinal losses. Enough fluid should be given to restore a good urine output. Other measures consist of broad-spectrum antibiotics (including anaerobic coverage), close monitoring of vital signs, physical examination, and laboratory studies (blood gases, white blood cell count, platelet count, and x-rays).
B. Surgical Treatment: Indications for surgery are evidence of perforation (free air present on a left lateral decubitus film), a fixed dilated loop of bowel on serial x-rays, abdominal wall cellulitis, or progressive deterioration despite maximal medical support. All of these signs are indicative of necrotic bowel. In the operating room, necrotic bowel is removed and ostomies are created. Reanastomosis is performed after the disease is resolved and the infant is bigger (usually > 2 kg and after 4-6 weeks).
Course & Prognosis
Infants managed either medically or surgically should not be refed until the disease is resolved (normal abdominal examination, resolution of pneumatosis on x-ray), usually in 10–14 days. Nutritional support during this time should be provided by total parenteral nutrition.
Death occurs in 10% of cases. Surgery is needed in less than 25% of cases. Long-term prognosis is determined by the amount of intestine lost. Infants with short bowel require long-term support with intravenous nutrition and therefore have very long hospitalizations. Even for those infants, however, the outcome is favorable because of improved parenteral nutrition formulations. Late strictures—about 3–6 weeks after initial diagnosis—occur in 8% of patients whether treated medically or surgically. Some of these strictures are severe enough to require operative management.
- Feeding intolerance with gastric aspirates or vomiting.
- Bloody stools.
- Abdominal distention and tenderness.
- Pneumatosis intestinalis on abdominal x-ray.
Necrotizing enterocolitis is the most common acquired gastrointestinal emergency in the newborn infant; it most often affects preterm infants, with an incidence of 10% in infants of birth weight less than 1500 g. In term infants, it occurs in association with polycythemia, congenital heart disease, and birth asphyxia. The pathogenesis of the disease is a multifactorial interaction between an immature gastrointestinal tract, mucosal injury, and potentially injurious factors in the lumen. Previous intestinal ischemia, bacterial or viral infection, and immunologic immaturity of the gut are thought to play a role in the genesis of the disorder. In up to 20% of affected infants, the only risk factor is prematurity.
Clinical Findings
The most common presenting sign is abdominal distention. Other signs include vomiting or increased gastric residuals, heme-positive stools, abdominal tenderness, temperature instability, increased apnea and bradycardia, decreased urine output, and poor perfusion. The complete blood count may show an increased white blood cell count with an increased band count or, as the disease progresses, absolute neutropenia. Thrombocytopenia is often observed along with stress-induced hyperglycemia and metabolic acidosis. Diagnosis is confirmed by the presence of pneumatosis intestinalis (air in the bowel wall) on x-ray. There is a spectrum of disease, and milder cases may exhibit only distention of bowel loops with bowel wall edema (thickened-appearing walls on x-ray).
Treatment
A. Medical Treatment: Necrotizing enterocolitis is managed by decompression of the gut by nasogastric tube, maintenance of oxygenation, mechanical ventilation if necessary, and intravenous fluids (colloid and normal saline) to replace third-space gastrointestinal losses. Enough fluid should be given to restore a good urine output. Other measures consist of broad-spectrum antibiotics (including anaerobic coverage), close monitoring of vital signs, physical examination, and laboratory studies (blood gases, white blood cell count, platelet count, and x-rays).
B. Surgical Treatment: Indications for surgery are evidence of perforation (free air present on a left lateral decubitus film), a fixed dilated loop of bowel on serial x-rays, abdominal wall cellulitis, or progressive deterioration despite maximal medical support. All of these signs are indicative of necrotic bowel. In the operating room, necrotic bowel is removed and ostomies are created. Reanastomosis is performed after the disease is resolved and the infant is bigger (usually > 2 kg and after 4-6 weeks).
Course & Prognosis
Infants managed either medically or surgically should not be refed until the disease is resolved (normal abdominal examination, resolution of pneumatosis on x-ray), usually in 10–14 days. Nutritional support during this time should be provided by total parenteral nutrition.
Death occurs in 10% of cases. Surgery is needed in less than 25% of cases. Long-term prognosis is determined by the amount of intestine lost. Infants with short bowel require long-term support with intravenous nutrition and therefore have very long hospitalizations. Even for those infants, however, the outcome is favorable because of improved parenteral nutrition formulations. Late strictures—about 3–6 weeks after initial diagnosis—occur in 8% of patients whether treated medically or surgically. Some of these strictures are severe enough to require operative management.
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