Pathophysiology

• Right-sided defect lateral to the base of the umbilical stalk through which a portion of the GI tract has herniated
  
• May be secondary to vascular accident with disruption of body wall formation or weakness at the insertion of the umbilical cord after involution of the right umbilical vein
  
• Exposure to amniotic fluid and partial closure of the defect may result in mesenteric vascular constriction → further bowel injury
  
• Bowel may be edematous and matted with inflammatory “peel”
  
• Small bowel with villous atrophy and blunting, muscular hypertrophy, and serosal inflammation

• Developmental arrest of somites in the abdominal wall or failure of midgut to return to the abdominal cavity after herniation into the umbilical stalk
  
• Central defect; umbilical ring fails to contract and leaves a round defect
  
• Defect is covered by a translucent mesenchymal membrane that protects the underlying abdominal organs from exposure to amniotic fluid
  
• The sac usually remains intact but occasionally is ruptured during delivery
  
• The liver and small intestine usually occupy part of the sac along with variable other abdominal organs

Epidemiology

• Sporadic; 1.5 of 10,000 live births
  
• Risk factors: Young maternal age; low SES; exposure to vasoconstricting decongestants, NSAIDs, cocaine, cigarette smoking, pesticides
  
• Can be associated with malrotation; associated with intestinal atresias in 5%–25%
  
• Not commonly associated with anomalies unrelated to the GI tract

• Sporadic; 2–2.5 of 10,000 live births
  
• Seen with mothers at extremes of reproductive age
  
• Associated with maternal obesity and SSRIs
  
• Associated with other structural or genetic defects in 50%–75%
  
• Associated syndromes: VACTERL association; Beckwith-Wiedemann syndrome; pentalogy of Cantrell; CHD; pulmonary hypoplasia; congenital malrotation of the colon; EEC syndrome; OEIS complex; trisomies 13, 18, and 21

Presentation and Diagnosis

• Usually diagnosed antenatally on US
  
• Mother has elevated AFP levels
  
• Most may still be delivered vaginally without further injury to the bowel

• Most diagnosed prenatally; should have a thorough evaluation for any other anomalies and consider chromosomal analysis
  
• Mother may or may not have elevated AFP levels

• May be delivered vaginally, but consider cesarean section for giant omphalocele because of concern for rupture

Treatment

• In delivery room, stabilize airway; wrap intestine with warm, sterile saline dressings; place-large bore orogastric tube to continuous suction; and place peripheral IV for fluid management and broad-spectrum antibiotics
  
• Place the infant in clear plastic bowel bag to minimize heat and water loss
  
• Inspect bowel for evidence of ischemia, torsion, and atresia
  
• Place the infant in lateral decubitus position to avoid mesenteric kinking
  
• Reduce or place the bowel in a sterile silo as soon as possible; delay may lead to bowel swelling and resultant ischemia
  
• If bowel is forced into abdominal cavity, may cause decreased diaphragmatic excursion, requiring increased ventilator support; may also impair mesenteric, hepatic, and renal perfusion
  
• During staged closure, parenteral nutrition, gastric decompression, and spontaneous breathing are preferred
  
• When reduction of silo contents is complete, final closure is performed
  
• Repair of atresias includes primary anastomosis, or if peel exists, internalization of uncorrected atresia and later reexploration and repair after peel resolves
  
• Await bowel sounds, passage of meconium, and cessation of bilious gastric aspirates before starting enteral feeds
  
• Conservative advancement of enteral feeds
  
• May have return of bowel function in a few days to weeks
  
• Those who fail to demonstrate bowel patency within 3–4 wk of closure should have contrast study to rule out unrecognized atresia
  
• Overall survival rate, 90%–95%; increased risk of third trimester fetal demise; most postnatal deaths are caused by perioperative complications (sepsis, NEC, abdominal visceral ischemia, late hepatic failure from TPN-associated cholestasis)

• In the delivery room, stabilize the airway; wrap the sac with warm, sterile saline dressings; place large-bore orogastric tube to continuous suction; and place peripheral IV for fluid management and broad-spectrum antibiotics
  
• Do not attempt reduction of the sac because it may rupture, cause respiratory compromise, or impair venous return
  
• Same management if the sac is ruptured; small rents in the sac may be sutured shut
  
• Small omphaloceles can often be closed in one-stage surgical repair
  
• Cases associated with significant other anomalies or large omphaloceles may be managed nonoperatively; the membrane is preserved and treated with silver sulfadiazine to allow epithelialization of the amnion over weeks or months, resulting in durable coverage; if the patient survives other conditions, he or she can have eventual closure later in childhood
  
• Survival rates are 30%–80% because of associated anomalies; with isolated omphalocele, survival rates approach those of gastroschisis
  
• Complications include GER, volvulus secondary to nonrotation, and ventral hernias
  
• Giant omphaloceles can be associated with pulmonary hypoplasia, and in severe cases, may cause neonatal death.

Pathophysiology

• Midgut = duodenum to transverse colon
  
• Undergoes two 270o counterclockwise rotations during 6–12 wk of gestation; improper rotation or fixation → narrow vascular pedicle with wide mesenteric base → obstruction and compromised blood supply
  
• Ladd bands form between ectopic cecum and right lateral abdominal wall and traverse the duodenum → intermittent, incomplete duodenal obstruction
  
• If fixation has not occurred normally, the intestine is susceptible to torsion on the axis of the SMA → gangrene of the midgut (almost uniformly fatal)

• Complete or partial; from intrinsic causes or external compression
  
• Intrinsic: Failure of recanalization of duodenum during 8–10 wk of gestation → solid from epithelial proliferation
  
• External: Annular pancreas; may encircle the second portion of the duodenum and cause obstruction
  
• Type I atresia: Luminal web or membrane, may be fenestrated; marked size discrepancy with mural continuity; often associated with anomalies of the common bile duct
  
• Type II atresia: Dilated proximal segment connected to small distal segment by a fibrous cord
  
• Type IIIA atresia (most common): Complete discontinuity between segments

• Potential causes: Ischemic insult to intestine, internal herniation of bowel, volvulus, bowel perforation, mesenteric thrombosis, epithelial plugging, lack of complete revacuolization of intestinal lumen
  
• Types I–IIIA as in duodenal atresia, plus:
  
• Type IIIB: “Apple peel” or “Christmas tree” deformity (distal small bowel segment forms a corkscrew around the terminus of the ileocecal artery)
  
• Type IV: Multiple atresias (“string of sausages” appearance); most often involve the proximal jejunum
  
• Dilatation of the bowel at the proximal end always occurs → large size discrepancy between the proximal and distal ends; dilated bowel has impaired peristalsis

Epidemiology

• 1 in 100 have some form of improper rotation or fixation; clinically significant disease occurs in one in 6000 live births
  
• Associated with CDH, omphalocele, and gastroschisis; may be associated with annular pancreas and bowel atresias

• 1 in 7000 live births; intrinsic duodenal atresia account for 50% of all small bowel atresias
  
• Associated with other conditions in 50%–80% of patients; most commonly trisomy 21 and CHD (30% each)
  
• Other anomalies: Intestinal malrotation (20%), esophageal atresia or imperforate anus (10%–20%), heterotaxy, biliary atresia, and gallbladder agenesis

• 50% in jejunum (30% proximal; 20% distal) and 50% in ileum (15% proximal; 35% distal)
  
• ~90% of small bowel atresias are single
  
• Associated with malrotation (10%–18%), meconium peritonitis (12%), meconium ileus (10%)
  
• 15%–30% associated with CF

Presentation

• Bilious emesis in any child <1 yr is malrotation until proven otherwise; emesis (bilious or not) is the most common presentation

• May have polyhydramnios (50%) and “double bubble” on antenatal US

• Antenatally: Polyhydramnios from inability of the fetus to absorb amniotic fluid and distended loops of fetal bowel on US caused by obstruction

• If intermittent obstruction is present, the patient may have periods of normal feeding with episodes of emesis
  
• Abdominal distension usually does not occur because the obstruction is high in the GI tract
  
• >50% present in the first month of life; 75% present within the first year
  
• Bloody stools and abdominal tenderness are ominous signs of vascular compromise; the patient may subsequently develop sepsis, shock, and luminal perforation

• Emesis of bile-stained fluid within hours of birth; 85% of obstructions are distal to the ampulla of Vater
  
• Swallowed air cannot pass the duodenum → distended upper abdomen and scaphoid lower abdomen
  
• May pass a small amount of meconium in the first 24 hr and then have no further stools

• Newborns: Abdominal distension and bilious vomiting and often failure to pass meconium
  
• Usually occur in otherwise normal newborns but rare cases are seen with other malformations

Diagnosis

• KUB: Duodenal obstruction, scant gas in rest of bowel; gasless abdomen may be seen when bowel infarction has occurred
  
• Gold standard is Upper GI with small bowel follow through: right-sided location of ligament of Treitz, spiraling or beaking of the duodenum suggesting obstruction
  
• US: Abnormal position of the SMV relative to the SMA
  
• Contrast enema: High cecum in the RUQ or failure of contrast to extend past the transverse colon (suggestive, but not conclusive, for malrotation).

• Abdominal radiography with classic “double-bubble” sign: Two distinct gas collections in the upper abdomen representing a dilated stomach and proximal duodenal bulb
  
• The distal abdomen may be gasless or have a small amount of air because of stenosis or fenestration of a duodenal web
  
• Diagnosis also suggested by aspiration of >30 mL gastric contents before feeding

• Abdominal radiography shows distended, air-filled bowel loops and multiple air-fluid levels
  
• Contrast enema may show microcolon because of little or no material passing distal to the obstruction

Treatment

• Initial treatment: Airway stabilization, placement of a large-bore nasal or orogastric tube to low-intermittent suction, peripheral IV placement, fluid resuscitation, correction of electrolyte abnormalities, and surgical consult

• Initial treatment: Airway stabilization, placement of large-bore nasal or orogastric tube to low intermittent suction, peripheral IV placement, fluid resuscitation, correction of electrolyte abnormalities, surgical consult, and thorough evaluation for other anomalies

• Initial treatment: Airway stabilization, placement of large-bore nasal or orogastric tube to low intermittent suction, peripheral IV placement, fluid resuscitation, correction of electrolyte abnormalities, and surgical consult

• Volvulus → surgical emergency; malrotation without signs of torsion is less urgent
  
• Ladd’s procedure: Manual inspection of the bowel, detorsion of volvulus, lysis of bands, passage of tube through the duodenum to rule out intraluminal obstruction, widening of the mesenteric base, incidental appendectomy, and nonrotational return of bowel to the abdomen
  
• If viability of the intestine is in question, the bowel should be detorsed and reexploration done in 24–36 h to reassess; infarcted areas should be resected and enterostomies created
  
• Mortality, 3%–9%; higher in patients with volvulus, necrosis, prematurity, or other abnormalities
  
• Complications: GI motility disturbances, recurrent volvulus, DIC, sepsis, short gut (if <40 cm small bowel left), reperfusion injury, small bowel obstruction, strictures

• Surgical treatment: Primary duodenoduodenostomy (preferred) or duodenojejunostomy to establish intestinal continuity
  
• GI function usually returns in 5–7 d, at which point enteral feeds can be initiated and progressively advanced
  
• Complications: Delayed transit caused by a persistently dilated and dyskinetic proximal duodenum; GER because of delayed gastric emptying
  
• Survival rate, 95%; morbidity and mortality are usually related to associated anomalies

• Operative intervention is based on the type of atresia, presence of comorbid conditions, and condition of the bowel at surgery
  
• The dilated proximal end is tapered or resected for end-to-oblique-end anastamosis
  
• Distal lumen of bowel is irrigated to ensure no other atretic segments or webs are present
  
• Multiple atresias are managed by multiple resections and anastomoses or by intramural stenting
  
• If bowel inflamed or ischemic, anastomosis is postponed, and diverting ostomy is performed
  
• Often require parenteral nutrition until bowel function returns; then may require elemental formulas to aid absorption before transitioning back to regular formula
  
• Complications: Anastomotic leakage, sepsis, strictures, impaired mobility, malabsorption