Necrotizing enterocolitis Alan Mathew Skaria TSMU
OverviewNecrotizing enterocolitis is the necrosis(death) of intestinal tissue. Itprimarily affects premature infants or sick newborns."Necrotizing" means the death oftissue, "entero" refers to the smallintestine, "colo" to the large intestine,and "itis" means inflammation.
Necrotizing Enterocolitis• One of the most serious GI diseases of neonates, especially preterm infants.• NEC involves infection and inflammation that causes destruction of the bowel (intestine) or part of the bowel• Intestinal necrosis that can involve all layers of the bowel.• Most commonly involves the ileum and colon but can occur anywhere.
Epidemiology• Most common GI emergency in newborns• Incidence 3 per 1000 live births• Incidence is 30 per 1000 live births for low birth weight neonates• 90% are premature• Incidence is 7% in newborns <1500 g• Race: blacks > non-Hispanic whites
Risk Factors• Prematurity (<34 weeks)• Low birth weight (<1500g) – Occurs in 2-10% of neonates <1500g• Enteral feeding of premature infants – Hypertonic formula/enteral meds – Breast milk protective compared to formula – Rate of feeds and timing of initiation of feeds don’t change rates of NEC• Term infant with pre-existing illness
Causes:• The exact cause of NEC is unknown• These premature infants have immature bowels, weakened by too little oxygen or blood flow. So when feedings are started, the added stress of food moving through the intestine allows bacteria normally found in the intestine to invade and damage the wall of the intestinal tissues. The damage may affect only a short segment of the intestine or can progress quickly to involve a much larger portion.
Pathogenesis:• A combination of risk factors predispose pts to NEC• An insult begins the process• Progression is due to stasis, bacterial overgrowth, vascular factors• May resolve, or may progress to perforation intenstine with gas bubbles in the intestinal wall and portions of the intestine that is frankly necrotic
Tests & diagnosis*Abdominal x-ray*Stool for occult blood test*Elevated white blood cell count in a CBC*Thrombocytopenia (low platelet count)*Lactic acidosis
Radiographic presentation• X-ray – Pneumatosis(gas cysts in the bowel wall) – Dilated loops of bowel – Portal air – Free air (if perforated) • Lateral decub is particularly helpful• Ultrasound – Good for bedside demonstration of ascites – May show portal air more clearly than KUB
Alimentary tract of infant showing intestinal necrosis, pneumatosis intestinalis, and perforationsite (arrow).
Modified Bell Staging for NECStage & Systemic Signs Abdominal Signs Radiographic SignsSeverityStage Ia Temp changes, apnea, Distension, gastric Normal, or intestinalSuspected NEC bradycardia, lethargy retention, emesis, heme dilation positive stool Mild ileusStage Ib Same as Ia Ia + grossly bloody Same as IaSuspected NEC stoolStage IIa Same as Ia Ib + absent bowel Intestinal dilation,Definite Mild NEC sounds +/- abdominal ileus, pneumatosis tenderness intestinalisStage IIb Ia + mild metabolic IIa + definite IIa + ascitesDefinite Moderate NEC acidosis, tenderness, +/- abd thrombocytopenia cellulitis, RLQ massStage IIIa IIb, but more severe, + IIb + peritonitis, Same as IIbAdvanced, Severe NEC combined respiratory & marked distension andBowel Intact metabolic acidosis, tenderness neutropenia, & DICStage IIIb Same as IIb Same as IIIa IIIa +Advanced Severe NEC pneumoperitoneumBowel Perforated Adapted from sources showing Bell Staging
Prevention• Encourage breast feeding – Breast fed babies have lower incidence than formula fed• No evidence shows that late initiation of enteral feeding or slow rate of feeding makes any difference• Maintain high level of suspicion – Feeding babies with NEC worsens the disease
Treatment•In an infant suspected of having necrotizing enterocolitis,feedings are stopped and gas is relieved from the bowel byinserting a small tube into the stomach.•Intravenous fluid replaces formula or breast milk.•Antibiotic therapy is started.•The infants condition is monitored with abdominal x-rays,blood tests, and blood gases.•Surgery will be needed if there is a hole in the intestines orperitonitis (inflammation of the abdominal wall).•The dead bowel tissue is removed and a colostomy orileostomy is performed.•The bowel is then reconnected several weeks or monthslater when the infection and inflammation have healed.
Prognosis•Depends on the severity of the illness•Necrotizing enterocolitis is a serious disease with a death rateapproaching 25%. Early, aggressive treatment helps improve theoutcome.•Most infants who develop NEC recover fully and do not have furtherfeeding problems.•In some cases, scarring and narrowing of the bowel may occur andcan cause future intestinal obstruction or blockage.•Another residual problem may be malabsorption (the inability of thebowel to absorb nutrients normally). This is more common in childrenwho required surgery for NEC and had part of their intestine removed.