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NEC is a syndrome of acute intestinal necrosis. The etiology is unknown and pathogenesis is complex and multi factorial. It is the most common serious surgical disorder among infants in NICU & a significant cause of neonatal morbidity and mortality. It is seen in 2.5% of all NICU admissions and has an overall mortality rate of 30-40% with mortality increasing to more than 80% in neonates less than 1kg.
There are various predisposing factors:
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Prematurity: Seen commonly at a mean gestational age of 30-32 wks. (AGA). It is the single greatest risk factor. Incidence of NEC increases as gestational age decreases.
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In Term infants & near terms : Conditions predisposing to decreased gastrointestinal oxygen delivery
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Perinatal asphyxia (lower 1 minute apgar score)
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Lower cord PH (acidosis)
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Polycythemia
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RDS / apnea
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Shock
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Umbilical artery catheterization
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Early / or large volume nasogastric feeding
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Congenital heart disease
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Pathogenesis
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- Role of immature Gastrointestinal host defenses
- Role of infectious agents & bacterial toxins
- Role of inflammatory mediators
- Role of oxygen radicals & ischemia reperfusion injury
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Pathology:
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Common sites are terminal ileum and ascending colon
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Clinical features:
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- Symptoms may appear within 96 hrs after initiation of feeds
- Majority of cases occur within first 10 days of life
- Onset may be insidious / explosive / delayed
- Earliest signs : abdominal distension, retention of milk in a sick-looking LBW infant.
- Clinical triad : Abdominal. Distension + GI bleeding + Pneumatosis intestinalis
- Signs of functional Intestinal obstruction : Abdominal distension, progressive decreased Peristalsis, Bilious vomiting, hematemesis and blood in stools
- Signs of peritonitis & perforation: Ascites, erythema & edema of abdominal wall, localized mass or rigidity
- Systemic signs : respiratory distress, Apnea / bradycardia, Lethargy, thermal instability, irritability, poor feeding, hypotension (shock), oliguria, bleeding diathesis, sclerema
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Clinical staging of NEC
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| Stage |
Clinical features |
X-ray |
Survival (%) |
| Suspect
NEC |
Mild abdominal distension
Stasis
Vomiting
Poor feeding |
Mild ileus |
100%
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| DefiniteNEC |
Marked abdominal distension
GI bleeding |
Definite ileus
Pneumatosis intestinalis |
95%
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Advanced
NEC |
DIC
Shock
Sclerema
Brownish Peritoneal aspirate |
Fixed dilated loop of intestine
Portal vein gas
Pneumoperitoneum |
50%
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INVESTIGATIONS:
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- Serial X-rays of abdomen: Fixed bowel loop, Appearance of mass, Pneumatosis intestinalis, Portal or hepatic venous air, Pneumoperitoneum
- Stool examination: Occult blood, reducing substances for unabsorbed lactose, Culture for aerobic / anaerobic bacteria
- Blood: Electrolytes, Hematocrit, Coagulation status , Culture, ABG. Watch for triad of thrombocytopenia, severe refractory hyponatremia and acidosis.
- USG: Micro bubbles of gas in portal vein
- Hydrogen breath test
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MANAGEMENT
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Medical
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Surgical |
Respiratory:
Supplement O 2
Mechanical ventilatory support
CVS:
Fresh frozen plasma
Low doses dopamine
Metabolic:
NaHCO
Nutrition:
Stop oral feedings (7-14 days)
TPN instituted (90-110 cal/kg/d)
Antibiotics - For 7-14 days. Broad spectrum
Hematological:
Platelet transfusions <BR> Packed RBCs
Vitamin K
CNS :
Treat IVH, meningitis, Seizures
Renal:
Fluid therapy |
Indications
- Bowel perforation
- Full thickness necrosis of bowel wall as evidenced by dilated loop of intestine unchanged in position > 24 hrs.
- Peritonitis. Aspiration of brown colored fluid is indicative of intestinal gangrene.
Surgical treatment:
Excision of necrotic area & end-to-end anastomosis.
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PROGNOSIS: |
Recurrent NEC is 4%.
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Sequelae:
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- Strictures (20%) most common in large bowel
- Enteric fistulas
- Short bowel syndrome (following surgery)
- Malabsorption & chronic diarrhea
- Dumping syndromes – loss of terminal ileum
- Fluids electrolyte losses (with ileostomy)
- Parenteral nutrition associated hepatic disease
- Developmental delay.
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Prevention
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- Corticosteroids – Prenatal / Postnatal
- Lower incidence of NEC in mothers of preterm who received
dexamethasone antenatally.
- Feeding regimen
- Breast feeding
- Acidified feeds
- Small iso-osmolar feeds with gradual increase in feeds
- Oral Immunoglobulins (IgA & IgG)
- Enhances intestinal immune defenses
- Reduce incidence of:
- Preterm delivery
- Prevent predisposing factors.
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DIFFERENTIAL DIAGNOSIS
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Pneumonia & sepsis
- Surgical abdominal catastrophes
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Malrotation with obstruction
- Malrotation with midgut volvulus
- Intusussception
- Ulcer
- Gastric perforation
- Mesenteric vessel thrombosis
- Infections enterocolitis with diarrhea
- Inherited metabolic disease
- Feeding intolerance
- Systemic candidiasis
Last updated: 1-05-2007
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How to cite this url |
Neonatal Necrotizing Enterocolitis (NEC).Pediatric Oncall [serial online] 2007 [cited 2007 May 1];4. Available from:
http://www.pediatriconcall.com/fordoctor/diseasesandcondition/Neonatology/NEC.asp
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