Necrotizing Enterocolitis

OverviewNecrotizing enterocolitis is the necrosis(death)

of intestinal tissue. It primarily affects premature infants or sick newborns.

"Necrotizing" means the death of tissue, "entero" refers to the small intestine, "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 neonates90% are premature Incidence is 7% in newborns <1500 gRace: 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 unknownThese 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

PRIMARY INFECTIOUS AGENTS

Bacteria, Bacterial toxin, Virus, Fungus

CIRCULATORY INSTABILITY

Hypoxic-ischemic event Polycythemia

MUCOSAL INJURY

ENTERAL FEEDINGS

Hypertonic formula or medication Malabsorption, gaseous distention H2 gas production, Endotoxin production

INFLAMMATORY MEDIATORS

Inflammatory cells (macrophage) Platelet activating factor (PAF) Tumor necrosis factor (TNF) Leukotriene C4, Interleukin 1; 6

Symptoms Abdominal distention

Blood in the stool

Diarrhea

Feeding intolerance

Lethargy

Temperature instability

Vomiting

Physiologic signs

Temperature instability

Apnea Episodes of

Bradycardias & Desaturation

Lethargy Acidosis Thrombocytopeni

a

Physical signs Feeding intolerance Increased gastric

residuals Abdominal distention Occult blood/

Hematochezia Peritonitis Discoloration of

abdominal wall Abdominal mass

Severe Abdominal Distension

Tests and DiagnosisAbdominal 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

Radiographic Signs

Alimentary tract of infant showing intestinal necrosis, pneumatosis intestinalis, and perforation site (arrow).

Modified Bell Staging for NEC

Stage &Severity

Systemic Signs Abdominal Signs Radiographic Signs

Stage IaSuspected NEC

Temp changes, apnea, bradycardia, lethargy

Distension, gastric retention, emesis, heme positive stool

Normal, or intestinal dilationMild ileus

Stage IbSuspected NEC

Same as Ia Ia + grossly bloody stool

Same as Ia

Stage IIaDefinite Mild NEC

Same as Ia Ib + absent bowel sounds +/- abdominal tenderness

Intestinal dilation, ileus, pneumatosis intestinalis

Stage IIbDefinite Moderate NEC

Ia + mild metabolic acidosis, thrombocytopenia

IIa + definite tenderness, +/- abd cellulitis, RLQ mass

IIa + ascites

Stage IIIaAdvanced, Severe NEC Bowel Intact

IIb, but more severe, + combined respiratory & metabolic acidosis, neutropenia, & DIC

IIb + peritonitis, marked distension and tenderness

Same as IIb

Stage IIIbAdvanced Severe NECBowel Perforated

Same as IIb Same as IIIa IIIa + pneumoperitoneum

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 by inserting a small tube into the stomach.

Intravenous fluid replaces formula or breast milk.

Antibiotic therapy is started. The infant's condition is monitored with

abdominal x-rays, blood tests, and blood gases.

Surgery will be needed if there is a hole in the intestines or peritonitis (inflammation of the abdominal wall).

The dead bowel tissue is removed and a colostomy or ileostomy is performed.

The bowel is then reconnected several weeks or months later when the infection and inflammation have healed.

Complications Intestinal perforation

Intestinal stricture

Peritonitis

Sepsis

Prognosis Depends on the severity of the illness Necrotizing enterocolitis is a serious

disease with a death rate approaching 25%. Early, aggressive treatment helps improve the outcome.

Most infants who develop NEC recover fully and do not have further feeding problems.

In some cases, scarring and narrowing of the bowel may occur and can cause future intestinal obstruction or blockage.

Another residual problem may be malabsorption (the inability of the bowel to absorb nutrients normally). This is more common in children who required surgery for NEC and had part of their intestine removed.