What is the most likely diagnosis for a preterm newborn with abdominal distention and air lucency in the bowel wall?

Necrotizing Enterocolitis (NEC)

The most likely diagnosis is A. Infection, specifically necrotizing enterocolitis (NEC), which is the correct answer for a preterm newborn presenting with abdominal distention and air lucency (pneumatosis intestinalis) in the bowel wall. 1

Diagnostic Reasoning

Pathognomonic Radiographic Finding

Pneumatosis intestinalis (air in the bowel wall) is the radiographic hallmark of NEC and directly corresponds to the "air lucency in the bowel wall" described in this case. 2 This finding, combined with abdominal distention in a premature infant, makes NEC the definitive diagnosis. 3

• NEC primarily affects premature infants and is the most common gastrointestinal emergency in this population. 1, 2
• The disease typically strikes during the first 2 weeks of life in preterm neonates. 2
• Air in the bowel wall (pneumatosis) represents bacterial invasion and gas production within the intestinal wall itself. 3

Clinical Presentation Pattern

The classic presentation includes: 1, 4

• Increased episodes of apnea and bradycardia (early signs)
• Abdominal distension (as seen in this case)
• Bloody stools
• Bilious emesis
• Portal venous gas may also be present on imaging 1

Why Other Options Are Incorrect

B. Malrotation presents with bilious vomiting and a "double bubble" sign on radiographs, not pneumatosis intestinalis. 1 Malrotation does not produce air in the bowel wall.

C. Meconium ileus shows distal bowel obstruction with multiple dilated loops and a microcolon on contrast enema, but does not produce pneumatosis intestinalis. 1

D. Esophageal atresia presents with inability to pass a nasogastric tube, excessive oral secretions, and choking with first feeding—not with abdominal distention or bowel wall air. 1

Pathophysiology

NEC requires three components: 1

• A substrate for bacterial growth (feedings)
• An infectious agent (usually bacterial)
• An event causing bowel damage (decreased blood flow/vascular compromise)

This leads to mucosal injury, pneumatosis intestinalis, bacterial overgrowth, and potential sepsis with full-thickness bowel injury or perforation. 1

Immediate Management Required

Once NEC is diagnosed, immediate intervention is critical: 5, 4

1. Complete bowel rest - discontinue all enteral feeds immediately
2. Nasogastric decompression - insert NG tube for bowel decompression
3. Broad-spectrum antibiotics - first-line options include ampicillin + gentamicin + metronidazole, or meropenem monotherapy 1, 4
4. Fluid resuscitation - address hemodynamic instability 5, 4
5. Surgical consultation - urgent intervention needed if perforation or clinical deterioration occurs 1, 5

Critical Pitfall to Avoid

Do not delay surgical consultation when pneumatosis is present, as the survival rate drops dramatically (from 95% to 40-90% mortality) when NEC involves the entire bowel, which occurs in approximately 25% of cases. 1, 5 Peritoneal drainage may be used in very low birth weight neonates as either temporizing or definitive treatment. 1