9.1 Congenital GI Abnormalities & NEC
Key Takeaways
- Omphalocele is a midline abdominal-wall defect covered by a membrane and often associated with chromosomal and cardiac anomalies; gastroschisis is a right paraumbilical defect with uncovered bowel and higher risk of fluid loss, hypothermia, and bowel injury.
- Malrotation with midgut volvulus presents with bilious emesis in a neonate or infant and is a surgical emergency; the upper GI series showing a corkscrew duodenum or abnormal ligament of Treitz location supports the diagnosis.
- Intussusception causes intermittent colicky pain, currant-jelly stool, and a sausage-shaped mass; air or hydrostatic enema is both diagnostic and therapeutic when there is no perforation or peritonitis.
- Hirschsprung disease is aganglionic distal bowel with failure to pass meconium, bilious vomiting, and risk of Hirschsprung-associated enterocolitis requiring rectal irrigation and urgent surgical evaluation.
- Necrotizing enterocolitis (NEC) is the leading surgical emergency of the preterm gut; pneumatosis intestinalis, portal venous gas, and free intraperitoneal air mark progressive disease requiring bowel rest, antibiotics, and often laparotomy or peritoneal drainage.
Congenital Abdominal-Wall Defects
Two classic neonatal abdominal-wall defects appear repeatedly on the CCRN Pediatric exam: omphalocele and gastroschisis. Both expose or displace bowel, but the embryology, associated anomalies, and bedside priorities differ, so exam items often ask you to match the defect to the risk profile rather than simply name the lesion.
Omphalocele is a midline herniation of abdominal contents into the base of the umbilical cord, covered by a translucent amnion-peritoneum membrane. Because the defect occurs early in embryogenesis, associated anomalies are common—chromosomal disorders (trisomy 13/18), congenital heart disease, Beckwith-Wiedemann syndrome, and other midline defects. Intact membrane covering reduces evaporative fluid loss relative to gastroschisis, but the membrane can rupture. Nursing priorities include protecting the sac with moist, nonadherent coverings, maintaining thermoregulation, decompressing the stomach with an orogastric tube, and supporting cardiopulmonary assessment while the team screens for associated anomalies before staged or primary closure.
Gastroschisis is a full-thickness abdominal-wall defect, typically to the right of the umbilicus, with bowel freely exposed—no covering membrane. Associated chromosomal anomalies are uncommon, but the exposed bowel is vulnerable to desiccation, hypothermia, fluid and protein loss, and constriction injury. Immediate care focuses on covering bowel with warm saline-soaked gauze and a bowel bag or silo, aggressive fluid resuscitation, temperature control, and early surgical consultation for silo reduction or primary closure. After closure, watch for abdominal compartment physiology, elevated peak airway pressures, and oliguria as abdominal domain is restored.
| Feature | Omphalocele | Gastroschisis |
|---|---|---|
| Location | Midline, cord base | Right paraumbilical |
| Covering | Membrane present | Bowel uncovered |
| Associated anomalies | Common (cardiac, genetic) | Uncommon |
| Early risk | Membrane rupture, associated disease | Fluid/heat loss, bowel injury |
| Closure strategy | Often staged if large | Silo or primary repair |
Malrotation, Volvulus, and Obstruction
Intestinal malrotation reflects incomplete rotation and fixation of the midgut, leaving a narrow mesenteric pedicle. When that pedicle twists, midgut volvulus cuts off superior mesenteric artery flow and can infarct the entire midgut within hours. The classic presentation is a previously well neonate or young infant with sudden bilious emesis. Abdominal findings may be deceptively mild early; do not wait for peritonitis. Immediate actions include NPO status, nasogastric or orogastric decompression, IV fluid resuscitation, broad-spectrum antibiotics if ischemia or perforation is suspected, and urgent surgical consultation. The diagnostic study of choice is an upper GI contrast series showing a corkscrew duodenum or failure of the duodenojejunal junction to cross the left of the spine. Free air or clinical peritonitis moves the child straight to the operating room.
Beyond volvulus, pediatric bowel obstruction spans atresias, meconium ileus (especially in cystic fibrosis), incarcerated hernia, and postoperative adhesions. Shared PICU priorities are decompression, fluid and electrolyte replacement for third-spacing into dilated bowel, serial abdominal exams, and early recognition of ischemia—worsening lactic acidosis, bloody stools, fixed loops, or peritonitis.
Intussusception
Intussusception—telescoping of proximal bowel into distal bowel—is the most common cause of intestinal obstruction in infants and toddlers, peaking between about 3 months and 3 years. Idiopathic ileocolic intussusception predominates; pathologic lead points (Meckel diverticulum, polyp, lymphoma) are more likely in older children or recurrent cases. The classic triad is intermittent colicky abdominal pain, currant-jelly (bloody mucus) stool, and a sausage-shaped abdominal mass, often with lethargy between pain episodes. Ultrasound showing a target or doughnut sign is highly suggestive. When there is no perforation or peritonitis, air or hydrostatic contrast enema is both diagnostic and therapeutic. Failed reduction, peritonitis, or perforation requires operative reduction and possible resection. Post-reduction monitoring watches for recurrence (highest in the first 24–48 hours), feeding tolerance, and evolving peritonitis.
Hirschsprung Disease
Hirschsprung disease is congenital aganglionosis of the distal bowel, most often limited to the rectosigmoid, causing functional obstruction. Neonates fail to pass meconium within 48 hours, develop abdominal distention and bilious vomiting, and may present later with chronic constipation and failure to thrive. The life-threatening complication is Hirschsprung-associated enterocolitis (HAEC): fever, explosive foul diarrhea or obstipation, toxic appearance, and rapid progression to shock. Management of HAEC includes rectal irrigations, bowel rest, IV fluids, antibiotics, and surgical consultation; definitive care is pull-through resection of the aganglionic segment after stabilization. Exam items often contrast HAEC with simple constipation—systemic toxicity and explosive stools signal enterocolitis, not routine bowel management.
Necrotizing Enterocolitis, Infarction, and Perforation
Necrotizing enterocolitis (NEC) is the leading acquired surgical emergency of the preterm intestine. Risk factors include prematurity, very low birth weight, enteral feeding (especially formula in vulnerable infants), circulatory instability, and bacterial colonization of an immature gut barrier. Pathophysiology combines mucosal ischemia, inflammation, and bacterial translocation, producing coagulative necrosis that can progress to full-thickness infarction and perforation.
Early clinical signs are feeding intolerance, gastric residuals, abdominal distention, guaiac-positive stools, apnea, temperature instability, and lethargy. Progressive disease adds abdominal wall erythema or discoloration, fixed loops, thrombocytopenia, metabolic acidosis, and hemodynamic instability. Radiographic hallmarks include pneumatosis intestinalis (intramural gas), portal venous gas, and pneumoperitoneum (free air) indicating perforation. Laboratory trends—falling platelets, rising lactate, neutropenia or left shift—support severity staging used at the bedside (Bell staging framework).
Medical management for suspected or proven NEC without free air includes bowel rest (NPO), gastric decompression, IV fluid resuscitation, parenteral nutrition, and broad-spectrum antibiotics covering enteric gram-negatives, gram-positives, and anaerobes. Serial exams and radiographs track progression. Absolute indications for operative intervention include pneumoperitoneum and refractory clinical deterioration suggesting dead bowel; relative indications include portal venous gas with progressive illness, abdominal wall cellulitis, and fixed dilated loops. Surgical options are laparotomy with resection and stoma creation, or primary peritoneal drainage in selected extremely low-birth-weight infants as a bridge or definitive strategy depending on institutional practice and response.
Bowel infarction from volvulus, vascular catastrophe, or advanced NEC shares a final common pathway: transmural necrosis, bacterial translocation, septic shock, and perforation. Free intraperitoneal air, rigid abdomen, and refractory lactate elevation demand operative source control. Postoperative PICU care emphasizes fluid resuscitation for third-space losses, antibiotic continuation, stoma assessment when present, and vigilant monitoring for short-bowel physiology if extensive resection was required.
Exam Integration
When the stem describes bilious emesis in a neonate, think malrotation/volvulus until proven otherwise. When it describes intermittent pain and currant-jelly stool, think intussusception and enema reduction if stable. When a preterm infant develops pneumatosis after feeds, think NEC and immediate bowel rest plus antibiotics. Matching defect anatomy (omphalocele vs gastroschisis) to associated anomalies and evaporative risk closes the congenital portion of this domain.
A newborn has a midline abdominal-wall defect at the umbilical cord base with a translucent covering over herniated bowel and liver. Which associated finding is most characteristic of this defect compared with gastroschisis?
A 10-day-old previously well infant develops sudden bilious emesis. The abdomen is soft without peritonitis. Which action best matches the suspected diagnosis of midgut volvulus?
A 28-week preterm infant on enteral feeds develops abdominal distention, guaiac-positive stools, thrombocytopenia, and abdominal radiographs showing intramural gas without free air. What is the priority PICU management step?