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Congenital High Intestinal Obstruction & Congenital Pyloric Stenosis

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Part I — Congenital High Intestinal Obstruction

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1. Duodenal Atresia & Stenosis

Embryology & Pathogenesis

Anatomic Variants (spectrum)

Associated Conditions

• Down syndrome (trisomy 21) — ~30% of cases
• Prematurity (~20%)
• Annular pancreas
• Maternal polyhydramnios (duodenal obstruction prevents normal absorption of swallowed amniotic fluid)
• Malrotation, preduodenal portal vein, biliary atresia
• Cardiac, renal, and anorectal malformations

Clinical Presentation

• Antenatal: polyhydramnios on maternal ultrasound; double-bubble sign may be seen in utero
• Postnatal: bilious vomiting within hours of birth; epigastric distension (distended stomach + proximal duodenum); failure to pass meconium normally

Diagnosis

• If distal gas is present, an upper GI contrast study should be performed to exclude malrotation with midgut volvulus (a surgical emergency)
• Prenatal ultrasound shows fluid-filled double-bubble in the fetal abdomen

Treatment

• Nasogastric/orogastric decompression; IV fluid resuscitation
• Definitive surgery: bypass of the obstruction — side-to-side or diamond-shaped (proximal transverse-to-distal longitudinal) duodenoduodenostomy
• Laparoscopic approach increasingly performed
• If proximal duodenum is markedly dilated: tapering duodenoplasty to reduce dysmotility
• For mucosal web: web fenestration or excision transduodenally (caution to protect the ampulla)

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2. Jejunoileal Atresia

Classification (Grosfeld Types)

Clinical Features

• Bilious vomiting, abdominal distension, failure to pass meconium
• Proximal atresias: prominent bilious emesis
• Distal atresias: abdominal distension with multiple dilated loops
• Contrast enema shows microcolon (unused, small caliber colon)
• Multiple atresias occur in 10–15% — distal bowel must be checked intraoperatively (saline injection via catheter)
• Associated with cystic fibrosis (~10%) — the only significant systemic association

Treatment

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3. Annular Pancreas (as a cause of high obstruction)

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Part II — Congenital Pyloric Stenosis (Infantile Hypertrophic Pyloric Stenosis)

Definition & Incidence

• Incidence: 1 in 300–900 live births (~0.2% of the general population)
• Male predominance: 4–5:1 (males affected more); first-born males at highest risk
• Typical presentation age: 2–8 weeks (range 3–12 weeks); rare after 12 weeks
• Siblings of affected patients: incidence rises to ~6%

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Pathology

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Etiology & Genetics

• Exact cause remains unknown
• High concordance in monozygotic twins; risk increased in dizygotic twins and siblings → strong familial/genetic component
• GWAS identified a locus at chromosome 11q23.3 (linked to cholesterol regulation)
• Turner syndrome and trisomy 18 confer increased risk
• Erythromycin or azithromycin exposure in the first 2 weeks of life (oral or via breast milk) is associated — macrolides are motilin receptor agonists, promoting excessive antral contractions

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Clinical Presentation

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Metabolic Consequences

Hypochloremic, hypokalemic metabolic alkalosis

• Loss of H⁺ and Cl⁻ → metabolic alkalosis + hypochloremia
• Kidneys initially excrete alkaline urine (high pH)
• As hypochloremia worsens, H⁺ is preferentially exchanged for Na⁺ in the distal tubule → paradoxical aciduria (urine becomes acidic despite systemic alkalosis)
• Low CO₂ from respiratory compensation: if anaesthesia is induced before correction, postoperative apnoea can occur due to absent CO₂ respiratory drive

• Serum bicarbonate < 30 mEq/L
• Serum chloride > 95 mEq/L
• Adequate urine output > 2 mL/kg/hr

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Diagnosis

• Pyloric muscle thickness > 3–4 mm
• Pyloric channel length > 15–18 mm

• If the "olive" is confidently palpated, no imaging is required
• Upper GI contrast study (used with caution — aspiration risk): delayed/absent passage of contrast through the pylorus; "string sign" or "beak sign" of the elongated, narrowed pyloric channel; used when ultrasound is equivocal or to exclude malrotation

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Treatment

Pyloric stenosis is NEVER a surgical emergency.

1. IV fluids: 20 mL/kg NS bolus; then D5 ½ NS + 20 mEq/L KCl at 1.5× maintenance until urine output established
2. Nasogastric tube decompression
3. Correct hypochloraemic alkalosis to safe targets before GA

• Longitudinal incision through the hypertrophied pyloric muscle (serosa down to submucosa) — does not enter the mucosa
• Key endpoint: bulging mucosa throughout the length of the incision + independent wall motion of the two muscle edges
• Mucosal perforation must be excluded by injecting air via nasogastric tube
• Approaches: laparoscopic (preferred — shorter stay, lower wound infection rate) or open (umbilical or right upper quadrant transverse incision)

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Summary Comparison

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Pediatric Surgery: Congenital GI & Thoracic Malformations

Complete Reference Guide

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PART 1 — ESOPHAGEAL ATRESIA (EA) & TRACHEOESOPHAGEAL FISTULA (TEF)

Definition & Incidence

• Incidence: 1 in 1500–3000 live births; mild male predominance
• ~33% have low birth weight
• 60–70% have associated anomalies — most important is the VACTERL association

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Embryology

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Classification (Gross-Vogt Types)

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Associated Anomalies — VACTERL

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Clinical Presentation

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Diagnosis

• CXR/AXR: OG tube coiled in proximal pouch; presence/absence of abdominal gas
  • Gas present → distal TEF (Type C)
  • Gas absent → pure EA (Type A)
• Oral contrast is contraindicated (aspiration risk)
• Bronchoscopy: defines fistula site and rules out laryngeal cleft; useful for planning surgery
• Echocardiography: mandatory — identifies cardiac anomalies + determines aortic arch side (determines surgical approach: left-sided arch → right thoracotomy; right-sided arch → left thoracotomy)
• Renal ultrasound: screens for associated renal anomalies

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Waterston Risk Classification (historical, still referenced)

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Pre-operative Management

1. Elevate head of bed 30–45° (prone if possible) — minimises aspiration
2. Replogle tube (double-lumen sump catheter) to continuous low suction — decompresses proximal pouch
3. Broad-spectrum IV antibiotics
4. Avoid intubation if possible — positive pressure ventilation preferentially inflates stomach via TEF, causing gastric distension and respiratory compromise
5. If ventilation required and gastric distension life-threatening → emergency gastrostomy to decompress
6. IV fluids, temperature maintenance

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Surgical Repair

1. Identify and ligate/divide the TEF flush with the trachea (avoid tracheal narrowing)
2. Mobilise the proximal pouch
3. Primary end-to-end oesophageal anastomosis (if gap allows)
4. Chest drain placed extrapleurally

• Delayed primary anastomosis (6–12 weeks) — upper pouch stimulated with bougie to encourage growth
• Foker technique: external traction sutures to lengthen both segments
• Oesophageal replacement: gastric transposition, colonic interposition, or jejunal interposition (as a last resort)

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Complications

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PART 2 — CONGENITAL HIGH INTESTINAL OBSTRUCTION

Overview

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A. Duodenal Atresia & Stenosis

Embryology & Pathogenesis

Anatomic Spectrum

Associated Conditions

• Down syndrome (Trisomy 21): ~30% — most important association
• Prematurity ~20%
• Annular pancreas
• Malrotation, biliary atresia, preduodenal portal vein
• Congenital heart disease, renal, anorectal malformations
• Maternal polyhydramnios (fetal swallowing of amniotic fluid is impaired)

Clinical Features

• Bilious vomiting within hours of birth (non-bilious if pre-ampullary)
• Epigastric distension (distended stomach + proximal duodenum)
• Failure to pass normal meconium
• Antenatal: double-bubble sign on fetal ultrasound

Diagnosis — The Double-Bubble Sign

• Two gas-filled chambers = distended stomach + proximal duodenum; no distal gas
• If distal gas IS present → incomplete obstruction (stenosis/web) or duodenoduodenal malrotation — upper GI contrast study required to exclude malrotation with midgut volvulus (surgical emergency)
• Antenatal USS: fluid-filled double-bubble; polyhydramnios

Treatment

1. Nasogastric decompression; IV fluids; temperature control
2. Echocardiography (Down syndrome + cardiac anomaly)
3. Definitive surgery: Duodenoduodenostomy — diamond-shaped anastomosis (proximal transverse to distal longitudinal) — bypasses the obstruction without resecting pancreatic tissue
   • Laparoscopic approach increasingly used
   • Markedly dilated proximal segment: tapering duodenoplasty
   • Mucosal web: transduodenal excision/fenestration — protect the ampulla of Vater

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B. Jejunoileal Atresia

Pathogenesis

Classification (Grosfeld)

Associated Conditions

• Cystic fibrosis ~10% (the key systemic association — sweat test mandatory)
• Generally NOT associated with chromosomal anomalies (unlike duodenal atresia)

Clinical Features

• Bilious vomiting + abdominal distension + failure to pass meconium
• Proximal atresias: dominant bilious emesis
• Distal atresias: prominent abdominal distension with multiple dilated loops on AXR
• Contrast enema: microcolon (unused, small calibre colon)
• Multiple atresias: always check entire bowel intraoperatively (saline injection via catheter)

Treatment

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C. Annular Pancreas

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PART 3 — CONGENITAL PYLORIC STENOSIS (Infantile Hypertrophic Pyloric Stenosis)

Definition & Incidence

• Incidence: 1 in 300–900 live births (~0.2% of general population)
• Male:female = 4–5:1; first-born males most at risk
• Peak presentation: 3–6 weeks of age (range 2–12 weeks; rare after 12 weeks)
• Sibling risk: ~6% (vs 0.2% general population)

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Pathology & Aetiology

• Deficiency of nitric oxide synthase in pyloric tissue (loss of smooth muscle relaxation)
• Genetic factors: high monozygotic twin concordance; GWAS locus at chromosome 11q23.3; siblings 30× increased risk
• Macrolide antibiotic exposure (erythromycin, azithromycin) in first 2 weeks of life — directly or via breast milk (motilin receptor agonism → excessive antral contractions)
• Associated with Turner syndrome and trisomy 18

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Clinical Presentation

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Metabolic Consequences

Hypochloraemic, Hypokalaemic Metabolic Alkalosis

1. Vomiting → loss of H⁺ + Cl⁻ → metabolic alkalosis + hypochloraemia
2. Kidney initially excretes alkaline urine (↑ pH)
3. As hypochloraemia worsens, H⁺ is exchanged for Na⁺ in distal tubule → paradoxical aciduria (urine becomes acid despite systemic alkalosis)
4. Low pCO₂ from respiratory compensation
5. Anaesthesia before correction → postoperative apnoea (absent CO₂ respiratory drive)

• Serum HCO₃⁻ < 30 mEq/L
• Serum Cl⁻ > 95 mEq/L
• Urine output > 2 mL/kg/hr

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Diagnosis

• Pyloric muscle thickness > 3–4 mm
• Pyloric channel length > 15–18 mm

• "String sign" or "beak sign" — elongated, narrowed pyloric channel
• Delayed/absent gastric emptying
• Reserved for equivocal cases or to exclude malrotation

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Treatment

Pyloric stenosis is NEVER a surgical emergency — resuscitate first.

Pre-operative Resuscitation

1. IV bolus 20 mL/kg normal saline
2. Maintenance: D5 ½ NS + 20 mEq/L KCl at 1.5× maintenance rate once urine output established
3. Nasogastric tube decompression
4. Correct until: HCO₃⁻ <30, Cl⁻ >95, urine output >2 mL/kg/hr

Surgery — Fredet-Ramstedt Pyloromyotomy

• Longitudinal incision through the hypertrophied pyloric muscle from the gastric antrum to the duodenum — extending through serosa and muscularis down to submucosa only (mucosa NOT entered)
• Endpoint: free bulging of mucosa + independent wall motion of the two muscle edges along the full length
• Test for mucosal injury: instil air via NG tube under saline — look for bubbles
• Approaches: Laparoscopic (preferred — shorter hospital stay, lower wound infection) or open (umbilical or right upper quadrant transverse incision)

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PART 4 — CONGENITAL DIAPHRAGMATIC HERNIA (CDH)

Definition & Incidence

• Incidence: 1 in 2000–5000 live births
• Survival: 65–90% at experienced centres
• Most cases are sporadic, isolated, non-syndromic
• Aetiology unknown; animal models implicate genetic, environmental, and nutritional factors

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Embryology & Types

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Pathophysiology

1. Pulmonary hypoplasia — smaller bronchi, reduced branching, reduced alveolar surface; both lungs affected (ipsilateral > contralateral)
2. Pulmonary hypertension — increased arteriolar smooth muscle thickness; extremely reactive vasculature
3. Mediastinal shift — compression of contralateral lung + cardiac displacement
4. Persistent pulmonary hypertension of the newborn (PPHN) — the most dangerous complication and main determinant of mortality

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Prenatal Diagnosis & Prognostic Markers

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Postnatal Clinical Presentation

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Postnatal Management

Immediate Stabilisation ("Gentle Ventilation" Principle)

1. Intubate immediately at delivery for severe cases — avoid bag-mask ventilation (inflates herniated bowel → further compression)
2. Nasogastric tube — immediate insertion to decompress bowel
3. "Gentle ventilation" strategy: limit peak inspiratory pressure (PIP <25 cmH₂O); permit permissive hypercapnia (pCO₂ 45–60 mmHg); target preductal SpO₂ 85–95%
4. Avoid high pressures — risk of pneumothorax in hypoplastic lung
5. Target: preductal SpO₂ >85%, post-ductal SpO₂ >70%

Pulmonary Hypertension Management

• iNO (inhaled nitric oxide) — selective pulmonary vasodilator; first-line for PPHN
• Sildenafil (PDE-5 inhibitor) — adjunct
• Prostaglandin E1 — maintains ductal patency if needed
• High-frequency oscillatory ventilation (HFOV) — improves gas exchange, reduces barotrauma
• ECMO (Extracorporeal Membrane Oxygenation) — reserved for refractory cases; bridge to surgery or recovery; criteria: oxygenation index >40, PaCO₂ >60 on maximal therapy

Timing of Surgery

CDH is NOT repaired immediately — surgery is delayed until the infant is physiologically stabilised

• Resolution of pulmonary hypertension
• Adequate oxygenation off/minimal vasopressors
• Urine output normalised
• Typically 48–72+ hours after birth

Surgical Repair

• Subcostal laparotomy (traditional, best exposure for liver/bowel reduction)
• Thoracoscopic repair (increasingly used for small-moderate defects)
• Thoracotomy (for right-sided CDH with liver herniation)

1. Reduce herniated abdominal contents into abdomen
2. Excise hernia sac (if present — ~10% have a sac)
3. Primary repair of diaphragmatic defect with non-absorbable sutures (if enough tissue)
4. For large defects (absent hemidiaphragm): prosthetic patch repair (Gore-Tex, Dacron) or muscle flap
5. Chest drain not routinely placed on repaired side (avoids mediastinal shift back)

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Long-Term Outcomes & Complications

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SUMMARY COMPARISON TABLE

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What's Included

1. Esophageal Atresia / TEF

• Embryology (4th week foregut division failure)
• Full Gross-Vogt classification with incidence diagram (Type C = 86%)
• VACTERL associations
• Clinical presentation + diagnostic algorithm
• Waterston classification
• Pre-operative management (Replogle tube, positioning, avoid PPV)
• Surgical repair (primary anastomosis, long-gap strategies, thoracoscopy)
• All complications (stricture, recurrent TEF, GOR, tracheomalacia)

2. Congenital High Intestinal Obstruction

• Duodenal atresia: failed recanalization, double-bubble sign (X-ray shown), Down syndrome association, diamond duodenoduodenostomy
• Jejunoileal atresia: vascular accident pathogenesis, Grosfeld types I–IV including apple-peel (Type IIIb), cystic fibrosis association, microcolon
• Annular pancreas: never divide the ring

3. Congenital Pyloric Stenosis

• Pathology, risk factors, macrolide association
• "Hungry vomiter" clinical picture, palpable olive
• Hypochloraemic hypokalaemic metabolic alkalosis + paradoxical aciduria
• US criteria (muscle >3–4 mm, length >15–18 mm)
• Pre-op resuscitation targets + Fredet-Ramstedt pyloromyotomy (image shown)

4. Congenital Diaphragmatic Hernia (CDH)

• Bochdalek vs Morgagni; embryology
• Pulmonary hypoplasia + PPHN pathophysiology
• LHR / O/E LHR prognostic markers; FETO fetal intervention
• "Gentle ventilation" strategy, iNO, ECMO criteria
• Delayed surgery principle; patch vs primary repair; long-term outcomes