Step 2 CK · Pediatrics

Neonatal GI Obstruction & Abdominal Wall Defects

Name: Neonatal GI Obstruction & Abdominal Wall Defects
Creator: Veli Bakalov, MD

A tube, a plain film, and a look at the belly wall name the lesion and the next move

Pediatrics·GI, Renal & Urology·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

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Polyhydramnios, frothy drooling, and choking or cyanosis at the first feed with an orogastric tube coiled in the upper pouch = esophageal atresia; gastric air means a distal TEF.
Esophageal atresia and imperforate anus both trigger a VACTERL screen: echocardiogram, renal ultrasound, spine and limb films.
Double bubble without distal gas = duodenal atresia (about 30% trisomy 21; annular pancreas) → NG decompression, IV fluids, duodenoduodenostomy.
Bilious vomiting with distal gas = rule out malrotation with midgut volvulus by emergent upper GI series, then Ladd procedure.
Jejunoileal atresia follows an in utero vascular accident: multiple air-fluid levels, microcolon, few extraintestinal anomalies.
Meconium ileus (soap-bubble RLQ, microcolon) = cystic fibrosis until proven otherwise → Gastrografin enema with IV fluids, then sweat chloride test.
Meconium plug/small left colon (infant of a diabetic mother) clears with a contrast enema; persistent symptoms → rectal suction biopsy and sweat test.
Imperforate anus: perineal fistula → anoplasty; no fistula by about 24 hours → colostomy, then posterior sagittal anorectoplasty; spinal ultrasound for tethered cord.
Gastroschisis (right of cord, no sac, isolated except atresia) → sterile bowel bag, warmth, IV fluids, early closure; omphalocele (midline sac; trisomy 13/18, Beckwith-Wiedemann, cardiac) → karyotype and echo; both raise maternal AFP.

Localizing obstruction in the newborn

Proximal versus distal. High obstruction (esophagus, duodenum) appears early: polyhydramnios because the fetus cannot swallow amniotic fluid, symptoms with the first feeds, and a flat abdomen. Low obstruction (ileum, colon, anus) brings progressive distension, later vomiting, and failure to pass meconium, which healthy term infants pass within 48 hours. Bilious vomiting places the block beyond the ampulla of Vater and is malrotation with volvulus until proven otherwise.

Neonatal obstruction at a glance

Lesion	Imaging hallmark	Next step
Esophageal atresia/TEF	Orogastric tube coils in the upper pouch; gastric air = distal fistula	Pouch suction, VACTERL screen, repair
Duodenal atresia	Double bubble, no distal gas	NG decompression, fluids, duodenoduodenostomy
Malrotation with volvulus	Distal gas often present; UGI: duodenojejunal junction right of midline, corkscrew	Emergent Ladd procedure
Jejunoileal atresia	Many dilated loops with air-fluid levels; microcolon	Resection and anastomosis
Meconium ileus	Few air-fluid levels, soap-bubble RLQ; microcolon	Gastrografin enema, then CF testing
Meconium plug / small left colon	Narrow left colon to the splenic flexure	Contrast enema; biopsy and sweat test if persistent

Esophageal atresia and tracheoesophageal fistula

Clinical picture. Polyhydramnios, then frothy drooling after birth with coughing, choking, or cyanosis at the first feed. About 85% have a blind upper pouch plus a distal tracheoesophageal fistula (TEF). Pure atresia leaves the abdomen gasless; an isolated H-type fistula presents later with coughing during feeds and recurrent pneumonia.

Diagnosis. An orogastric tube cannot be advanced and coils in the upper pouch on chest X-ray; air in the stomach proves a distal fistula. Barium is avoided because of aspiration.

Stabilization and repair. NPO, continuous upper-pouch suction (Replogle tube), and head elevation so acid does not reflux through the fistula into the lungs; avoid vigorous bag-mask ventilation, which inflates the stomach through the fistula. Surgery ligates the fistula and joins the esophagus; stricture, leak, reflux, and tracheomalacia can follow.

VACTERL: vertebral, anal, cardiac, tracheoesophageal, renal, limb (radial ray). Before surgery obtain an echocardiogram (defects and aortic arch side, which guides the thoracotomy), renal ultrasound, and spine and limb films.

Duodenal, jejunoileal, and meconium obstruction

Duodenal atresia. Failed recanalization of the duodenum. Most lie below the ampulla, so bilious vomiting starts on day 1, with polyhydramnios and a nondistended abdomen; the film shows a double bubble with no distal gas. About 30% have trisomy 21; annular pancreas and cardiac defects are also linked. Treat with NG decompression, IV fluids, electrolyte correction, and an elective duodenoduodenostomy.

Bilious vomiting with some distal gas suggests malrotation with midgut volvulus: emergent upper GI series and Ladd procedure before the midgut infarcts.

Jejunoileal atresia. An in utero mesenteric vascular accident (such as fetal volvulus or intussusception), so extraintestinal anomalies are uncommon. Bilious vomiting and distension that is greater the more distal the lesion; resection with anastomosis, with a risk of short bowel syndrome.

Meconium ileus. Inspissated meconium obstructs the terminal ileum; 80–90% of affected infants have cystic fibrosis, often as its first sign. A hyperosmolar water-soluble (Gastrografin) enema is diagnostic and often therapeutic, drawing water into the lumen, so give generous IV fluids. Perforation, meconium peritonitis (calcifications), or volvulus requires surgery. Confirm CF with a sweat chloride test or CFTR genetic testing.

Meconium plug and small left colon. Transient colonic immaturity, classically in infants of diabetic mothers or after maternal magnesium sulfate. The contrast enema usually expels the plug; persistent symptoms call for a rectal suction biopsy (Hirschsprung disease) and a sweat test.

Imperforate anus

Find the fistula. Look for meconium on the perineum, along the scrotal raphe, or in the vestibule, and for meconium in the urine (rectourinary fistula). Meconium takes time to emerge, so re-examine at about 24 hours. A perineal fistula gets primary anoplasty; no fistula means a diverting colostomy, then posterior sagittal anorectoplasty.

Associations. Screen for VACTERL anomalies and for a tethered spinal cord with spinal ultrasound, since tethering threatens bowel, bladder, and leg function.

Abdominal wall defects

Gastroschisis versus omphalocele

Feature	Gastroschisis	Omphalocele
Location	Right of an intact cord	Midline, through the umbilical ring
Covering	None; thickened, edematous, matted bowel	Membranous sac; cord inserts on it
Contents	Bowel	Bowel, often liver
Anomalies	Rare; intestinal atresia in about 10%	More than half: trisomy 13/18, Beckwith-Wiedemann, cardiac, pentalogy of Cantrell
Risk factors	Maternal age <20, smoking, vasoactive drugs	Chromosomal and genetic syndromes
Maternal AFP	Elevated (higher)	Elevated

Gastroschisis. A full-thickness defect beside the cord with no sac; bowel bathed in amniotic fluid thickens and mats, and ischemia at the narrow defect causes the associated atresias.

Protect the bowelsterile clear bowel bag, or warm saline gauze under plastic wrap; infant on its side so the mesentery does not kink
Supportorogastric decompression; warmth, IV fluids, and antibiotics for large evaporative losses
Close earlyprimary closure or staged silo reduction; prolonged ileus often needs TPN

Omphalocele. The midgut normally returns to the abdomen by weeks 10–12; failure leaves bowel, sometimes liver, in a midline sac. Obtain a karyotype, echocardiogram, and serial glucose checks. Small defects are closed primarily; giant ones are painted with a topical agent (such as silver sulfadiazine) to epithelialize, with delayed closure.

Beckwith-Wiedemann syndrome (macroglossia, macrosomia, hemihypertrophy) causes neonatal hypoglycemia from islet hyperplasia and later Wilms tumor and hepatoblastoma risk.