Pyloric Stenosis

Overview

Pyloric stenosis is a condition that affects infants, typically between 2 to 8 weeks of age, though it can occur up to 6 months. The condition involves the abnormal thickening (hypertrophy) of the pylorus, the muscular valve between the stomach and small intestine. This thickening causes a narrowing of the pyloric channel, preventing food from passing from the stomach into the duodenum (first part of the small intestine). As a result, infants forcefully vomit after feeding, leading to dehydration and failure to gain weight.

The condition affects approximately 2-3 out of every 1,000 babies born in the United States, making it one of the most common conditions requiring surgery in infancy. Pyloric stenosis is four to five times more common in males than females, and firstborn children are at higher risk. The incidence also varies by ethnicity, being more common in Caucasian infants compared to African American or Asian infants. While the exact cause remains unknown, both genetic and environmental factors appear to play a role.

Before the development of surgical treatment in 1912, pyloric stenosis was often fatal due to severe dehydration and electrolyte imbalances. Today, with early recognition and surgical intervention (pyloromyotomy), the prognosis is excellent. The surgery has a success rate of nearly 100%, and most infants can begin feeding within hours after the procedure. Following successful treatment, babies typically experience no long-term effects and go on to lead normal, healthy lives. The key to optimal outcomes is prompt recognition of symptoms and timely medical intervention.

Symptoms

The symptoms of pyloric stenosis typically begin gradually and worsen over days to weeks. Parents often notice changes in their baby's feeding patterns and behavior that progressively become more concerning.

Primary Symptoms

Observable Physical Signs

Vomiting Characteristics

• Non-bilious: Vomit contains milk/formula but no bile (green color)
• Progressive: Starts as spitting up, progresses to projectile
• After most feedings: Eventually occurs after nearly every feeding
• May contain blood: Small streaks from irritated stomach lining
• Coffee-ground appearance: In severe cases with stomach irritation

Signs of Dehydration

• Decreased urination (fewer than 4 wet diapers in 24 hours)
• Dark yellow or amber urine
• Sunken soft spot (fontanelle) on baby's head
• Sunken eyes
• Dry lips and mouth
• Crying without tears
• Lethargy or decreased activity
• Cool, mottled skin

Metabolic Changes

• Hypochloremic alkalosis: Loss of stomach acid leads to electrolyte imbalances
• Hypokalemia: Low potassium levels
• Jaundice: Mild yellowing of skin in some cases
• Lethargy: From electrolyte imbalances and dehydration

Causes

The exact cause of pyloric stenosis remains unknown, but research suggests a combination of genetic and environmental factors contribute to its development. The condition involves progressive thickening of the pyloric muscle after birth.

Anatomical Changes

• Muscle hypertrophy:
  • Circular muscle layer thickens abnormally
  • Longitudinal muscle also affected
  • Pyloric channel becomes narrowed and elongated
  • Progressive obstruction develops over weeks
• Cellular changes:
  • Increased muscle cell size (hypertrophy)
  • Increased muscle cell number (hyperplasia)
  • Nerve abnormalities in pyloric muscle
  • Reduced nitric oxide synthase activity

Genetic Factors

• Familial clustering:
  • 20-fold increased risk if parent had pyloric stenosis
  • Higher concordance in monozygotic twins
  • Multiple genetic loci identified
  • Polygenic inheritance pattern
• Associated genetic syndromes:
  • Cornelia de Lange syndrome
  • Smith-Lemli-Opitz syndrome
  • Trisomy 18
  • FoxF1 mutations

Environmental Factors

• Early antibiotic exposure:
  • Erythromycin in first 2 weeks of life
  • Azithromycin exposure
  • Maternal antibiotic use during pregnancy
  • Disruption of gut microbiome proposed
• Feeding factors:
  • Formula feeding (slight increased risk)
  • Prostaglandin E in breast milk (protective)
  • Early feeding practices
• Other associations:
  • Maternal smoking during pregnancy
  • Young maternal age
  • Cesarean delivery (controversial)
  • Seasonal variation (higher in spring/summer)

Proposed Mechanisms

• Neuronal dysfunction: Abnormal innervation of pyloric muscle
• Smooth muscle abnormalities: Primary muscle cell dysfunction
• Hormonal factors: Gastrin, serotonin imbalances
• Inflammatory processes: Local inflammation triggering hypertrophy
• Developmental arrest: Failure of normal pyloric maturation

Risk Factors

Several factors increase an infant's risk of developing pyloric stenosis:

Demographic Factors

• Gender: Males 4-5 times more likely than females
• Birth order: Firstborn children at higher risk (30% of cases)
• Ethnicity:
  • Highest in Caucasians
  • Intermediate in Hispanics
  • Lower in African Americans
  • Lowest in Asians
• Age: Peak incidence at 3-5 weeks of life
• Prematurity: Premature infants may present later

Family History

• Parental history:
  • If mother had PS: 19% risk for sons, 7% for daughters
  • If father had PS: 5% risk for sons, 2.5% for daughters
  • Multiple affected family members increase risk
• Sibling history:
  • 5% risk if sibling affected
  • Higher if multiple siblings affected
  • Twin concordance suggests genetic component

Prenatal and Perinatal Factors

• Maternal factors:
  • Young maternal age (<20 years)
  • Maternal smoking during pregnancy
  • Maternal stress during pregnancy
  • Maternal antibiotic use
• Birth factors:
  • Cesarean delivery (debated)
  • Birth weight variations
  • Perinatal complications

Postnatal Exposures

• Antibiotic exposure:
  • Erythromycin in first 14 days (8-fold increased risk)
  • Azithromycin exposure
  • Treatment for pertussis prophylaxis
• Feeding method:
  • Formula feeding (slight increase)
  • Early introduction of solids (no clear association)

Diagnosis

Diagnosis of pyloric stenosis involves clinical evaluation, imaging studies, and laboratory tests to confirm the condition and assess the infant's metabolic status.

Clinical Evaluation

• History taking:
  • Feeding history and vomiting pattern
  • Weight gain/loss trajectory
  • Urination and stool patterns
  • Family history of pyloric stenosis
  • Antibiotic exposure
• Physical examination:
  • Weight and growth parameters
  • Hydration status assessment
  • Abdominal palpation for "olive"
  • Observation of peristaltic waves
  • Signs of dehydration

Ultrasound (Gold Standard)

• Diagnostic criteria:
  • Pyloric muscle thickness >3 mm (some use >4 mm)
  • Pyloric channel length >15-17 mm
  • Pyloric diameter >13 mm
  • Failure of pyloric channel to open during exam
• Advantages:
  • No radiation exposure
  • High sensitivity and specificity (>95%)
  • Can visualize gastric distension
  • Real-time assessment

Upper GI Series (Barium Study)

• When used:
  • If ultrasound non-diagnostic
  • To rule out other conditions
  • Less commonly used now
• Findings:
  • "String sign" - thin contrast through pylorus
  • "Shoulder sign" - bulge of pyloric muscle
  • Delayed gastric emptying
  • Active gastric hyperperistalsis

Laboratory Tests

• Electrolyte panel:
  • Hypochloremic metabolic alkalosis (classic)
  • Hypokalemia
  • Hyponatremia in severe cases
  • Elevated bicarbonate
• Other tests:
  • Complete blood count
  • Blood glucose
  • Bilirubin (if jaundiced)
  • BUN and creatinine (assess dehydration)

Differential Diagnosis

• Gastroesophageal reflux disease (GERD)
• Malrotation with volvulus (bilious vomiting)
• Duodenal atresia (presents earlier)
• Antral or duodenal web
• Milk protein allergy
• Metabolic disorders
• Increased intracranial pressure
• Urinary tract infection
• Overfeeding

Treatment Options

Treatment of pyloric stenosis involves initial medical stabilization followed by surgical correction. The approach is highly standardized with excellent outcomes.

Pre-operative Management

• Fluid resuscitation:
  • IV access establishment
  • Normal saline or lactated Ringer's boluses
  • Maintenance fluids with dextrose
  • Goal: normal urine output (1-2 mL/kg/hr)
• Electrolyte correction:
  • Correct hypochloremic alkalosis first
  • Potassium replacement after adequate urine output
  • Goal: Chloride >100 mEq/L, bicarbonate <30 mEq/L
  • May take 24-48 hours
• Other measures:
  • NPO (nothing by mouth)
  • Nasogastric decompression if needed
  • Monitor glucose in small infants
  • Parental support and education

Surgical Treatment - Pyloromyotomy

• Ramstedt pyloromyotomy (gold standard):
  • Longitudinal incision through pyloric muscle
  • Spreads muscle fibers without cutting mucosa
  • Immediately relieves obstruction
  • Success rate >99%
• Surgical approaches:
  • Laparoscopic (most common):
    • 3 small incisions
    • Faster recovery
    • Better cosmetic result
    • Shorter hospital stay
  • Open approach:
    • Right upper quadrant incision
    • Periumbilical incision
    • Used if laparoscopy fails

Post-operative Care

• Feeding protocol:
  • Start feeds 4-6 hours post-op
  • Small frequent feeds initially
  • Gradual advancement over 24-48 hours
  • Return to normal feeding by discharge
• Pain management:
  • Acetaminophen usually sufficient
  • Local anesthetic at incision sites
  • Minimal narcotic requirement
• Monitoring:
  • Vital signs
  • Feeding tolerance
  • Vomiting (common initially)
  • Wound assessment

Non-surgical Management

• Atropine therapy (rarely used):
  • Historical treatment option
  • IV atropine before feeds
  • 4-6 week treatment course
  • High failure rate, side effects
  • Reserved for extreme surgical risk
• Endoscopic balloon dilation:
  • Experimental approach
  • High recurrence rate
  • Not standard practice

Outcomes and Prognosis

• Immediate outcomes:
  • Hospital stay 1-2 days
  • Full feeding within 48 hours
  • Rapid weight gain
  • Resolution of symptoms
• Long-term outcomes:
  • Normal growth and development
  • No dietary restrictions
  • No increased risk of GI problems
  • Excellent cosmetic results with laparoscopy

Prevention

While pyloric stenosis cannot be completely prevented due to its multifactorial nature, certain measures may reduce risk:

Prenatal Measures

• Maternal health:
  • Avoid smoking during pregnancy
  • Maintain healthy pregnancy weight
  • Minimize unnecessary antibiotic use
  • Manage stress during pregnancy
• Genetic counseling:
  • For families with multiple affected members
  • Understanding recurrence risks
  • No specific genetic testing available

Postnatal Considerations

• Antibiotic stewardship:
  • Avoid erythromycin in first 2 weeks if possible
  • Use alternative antibiotics when appropriate
  • Weigh risks vs benefits
  • Monitor infants exposed to macrolides
• Early recognition:
  • Educate parents about warning signs
  • Prompt evaluation of persistent vomiting
  • Regular weight checks in early infancy
  • Higher vigilance for at-risk infants

Breastfeeding Considerations

• Breastfeeding may have slight protective effect
• Continue breastfeeding if possible
• No dietary restrictions for nursing mothers
• Pumping during hospitalization if needed

When to See a Doctor

Early recognition and treatment of pyloric stenosis is crucial for preventing complications. Parents should be aware of warning signs:

Seek Immediate Medical Attention If:

• Projectile vomiting after feedings
• Vomiting that becomes more forceful over time
• Baby seems constantly hungry after vomiting
• Weight loss or failure to gain weight
• Decreased number of wet diapers
• No bowel movements for 1-2 days
• Lethargy or unusual sleepiness
• Sunken soft spot on baby's head

Emergency Warning Signs:

• Signs of severe dehydration (no tears, dry mouth)
• Blood in vomit
• Coffee-ground appearance to vomit
• Extreme irritability or inconsolable crying
• Cool, mottled skin
• Rapid breathing or heart rate
• Inability to keep any fluids down

What to Tell Your Doctor:

• When vomiting started and how it has progressed
• Description of vomiting (forceful, after every feeding)
• Baby's feeding schedule and amounts
• Number of wet and dirty diapers
• Any weight loss or poor weight gain
• Family history of pyloric stenosis
• Recent antibiotic use
• Birth history and current age

Follow-up After Surgery:

• Surgical site redness, swelling, or drainage
• Fever above 100.4°F (38°C)
• Persistent vomiting after surgery
• Poor feeding after discharge
• Signs of dehydration
• Excessive crying or apparent pain

Related Conditions

References

1. Peters B, et al. Advances in infantile hypertrophic pyloric stenosis. Expert Review of Gastroenterology & Hepatology. 2014;8(5):533-541.
2. Jobson M, Hall NJ. Contemporary management of pyloric stenosis. Seminars in Pediatric Surgery. 2016;25(4):219-224.
3. Krogh C, et al. Familial aggregation and heritability of pyloric stenosis. JAMA. 2010;303(23):2393-2399.
4. Pandya S, Heiss K. Pyloric stenosis in pediatric surgery: an evidence-based review. Surgical Clinics of North America. 2012;92(3):527-539.
5. Almaramhy HH. Laparoscopic versus open pyloromyotomy for infantile hypertrophic pyloric stenosis: a retrospective study. Annals of Pediatric Surgery. 2021;17(1):1-6.
6. American Academy of Pediatrics. Hypertrophic Pyloric Stenosis in Infants Following Pertussis Prophylaxis with Erythromycin. Pediatrics. 1999;103(6):1-3.