What are the clinical presentation, diagnostic criteria, treatment approach, and preventive measures for necrotizing enterocolitis in a premature infant weighing less than 1500 g who develops symptoms within the first two weeks after initiation of enteral feeds?

Necrotizing Enterocolitis in Premature Infants <1500g

For a premature infant <1500g developing symptoms within two weeks of enteral feeding initiation, immediately implement bowel rest with complete cessation of feeds, nasogastric decompression, aggressive fluid resuscitation, and broad-spectrum antibiotics (ampicillin + gentamicin + metronidazole), while obtaining urgent surgical consultation if perforation or clinical deterioration occurs. 1, 2

Clinical Presentation

The disease typically manifests with a characteristic progression of symptoms:

Early warning signs:

• Increased episodes of apnea and bradycardia 3, 4
• Feeding intolerance and abdominal distension 4
• Bilious emesis 3, 4
• Occult blood in stools progressing to frank bloody stools 3, 4

Advanced disease indicators:

• Persistent or worsening abdominal distension with absent bowel sounds 4
• Focal abdominal wall erythema or edema 3, 4
• Signs of sepsis including thrombocytopenia, neutropenia, and acidosis 3
• Hemodynamic instability requiring vasopressor support 4

Diagnostic Criteria

Radiographic findings:

• Pneumatosis intestinalis (air in the bowel wall) is the radiographic hallmark 3
• Portal venous gas may be present 3
• Pneumoperitoneum indicates perforation and mandates surgical intervention 1

Pathophysiology triad: The disease requires three components: substrate for bacterial growth (feedings), infectious agent (usually bacterial), and bowel damage from vascular compromise 3

Treatment Algorithm

Immediate Medical Management (All Cases)

Step 1: Bowel rest and decompression

• Complete cessation of all enteral feeds to prevent further intestinal injury 1, 2
• Nasogastric decompression to prevent gastric distension and reduce perforation risk 1

Step 2: Hemodynamic stabilization

• Aggressive fluid resuscitation to address hypovolemia and prevent septic shock 1

Step 3: Antibiotic therapy

• First-line regimen: Ampicillin + gentamicin + metronidazole 3, 1
• This three-drug combination has been the most commonly used regimen for decades in pediatric complicated intra-abdominal infections 3
• Individualized daily aminoglycoside dosing according to lean body mass and estimated extracellular fluid volume 3

Alternative regimens (if first-line unavailable):

• Carbapenems (imipenem or meropenem) 3
• Piperacillin-tazobactam 3
• Extended-spectrum cephalosporin (cefotaxime, ceftriaxone, ceftazidime, or cefepime) with metronidazole 3

Surgical Decision-Making

Approximately 70% of cases can be managed nonoperatively, while 30% require surgical intervention 1, 4

Mandatory surgical indications:

• Confirmed bowel perforation (pneumoperitoneum on imaging) 1
• Clinical deterioration despite maximal medical therapy 1, 2

Surgical options:

• For very low birth weight neonates with perforation: peritoneal drainage may be used as initial intervention or temporizing measure 3
• Definitive operation: bowel resection with stoma creation or reanastomosis 3

Nutritional Support During Acute Phase

Total parenteral nutrition requirements:

• Minimum amino acid intake of 1.0 g/kg/day to prevent negative nitrogen balance 1, 2
• Ensure 30-40 Kcal per 1g amino acids for proper amino acid utilization 1, 2
• Include taurine in amino acid solutions (optimal dosing uncertain) 1, 2

Important caveat: Glutamine supplementation is NOT recommended for infants up to two years of age with NEC 2

Prevention Strategies

Primary Prevention (Before NEC Onset)

Probiotic supplementation is an effective prophylactic measure 3

Recommended probiotic combinations with high-quality evidence:

• L. rhamnosus ATCC 53103 + B. longum subsp infantis 1
• L. casei + B. breve 1
• L. acidophilus + B. longum subsp infantis 1
• L. acidophilus + B. bifidum 1

These combinations have demonstrated reduction in all-cause mortality and severe NEC 1

Secondary Prevention (After Recovery)

When reintroducing feeds:

• Consider arginine supplementation to help prevent NEC recurrence 1, 2
• Continue probiotic supplementation, specifically combinations of Lactobacillus spp. and Bifidobacterium spp. 1, 2

Prognostic Information

Overall survival is approximately 95% unless the entire bowel is involved 3, 1, 4, 2

Critical prognostic factors:

• When entire bowel is involved (~25% of cases): mortality increases dramatically to 40-90% 3, 1, 4
• Gestational age significantly impacts incidence:
  • 23-24 weeks: 10-20% incidence 1, 4
  • 25-27 weeks: 5-10% incidence 1, 4
  • ≥28 weeks: <5% incidence 1, 4

Late complications:

• Intestinal stricture occurs in 15-35% of recovered infants 5

Common Pitfalls to Avoid

• Do not delay surgical consultation when perforation is suspected—mortality increases significantly with delayed intervention 1
• Do not continue enteral feeds in symptomatic infants—complete bowel rest is mandatory 1, 2
• Do not use glutamine supplementation—it is not recommended and lacks evidence in this population 2
• Monitor closely if attempting catheter salvage in infants with central line-related bloodstream infections, as vascular access difficulties in premature infants sometimes necessitate treatment without catheter removal 3