Pyloric Stenosis

Summary

Introduction

• Infantile hypertrophic pyloric stenosis (IHPS) is a congenital hypertrophy of pyloric smooth muscle (leads to pyloric narrowing and gastric outlet obstruction).
• This condition classically presents in an infant age 3-6 weeks after birth as projectile nonbilious vomiting, visible peristalsis, olive-like mass in the abdomen (more common in first born males).
• Multiple conditions are associated with pyloric stenosis (Down syndrome, eosinophilic gastroenteritis, hypergastrinemia).
• Definitive treatment is surgery (pyloromyotomy).

Epidemiology

• Caucasians and first born male infants are more commonly affected (male-to-female ratio is 4:1).

Etiology

• Etiology is unknown.
• Primary risk factors are male gender and a positive family history of pyloric stenosis.
• Other risk factors include; younger maternal age, preterm birth, maternal smoking during pregnancy, formula feeding and postnatal exposure to macrolide antibiotics.

Presentation

• Nonbilious (nonbloody) milky projectile (forceful) vomiting (occurs shortly after feeding) that starts the second or third week of life.
• Palpable olive-shaped mass in the epigastrium.
• Visible gastric peristalsis.
• In the early stage of disease, the infant remains hungry post-vomiting.
• In cases of delay in diagnosis, complications can include; dehydration, poor weight gain, malnutrition and metabolic alterations.
• Jaundice officers in 5% of infants (associated with low levels of the enzyme glucuronyl transferase).

Physical Examination

• Palpable hypertrophic pyloric muscle just above and to the right of the umbilicus (referred to as the “olive”).
• Visible gastric peristalsis.

Imaging

• Thickening of pyloric muscle on abdominal ultrasound (imaging of choice).
• Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered diagnostic.
• When abdominal ultrasound is not diagnostic, barium upper GI study can be used (may show double track sign or string sign).

Labs

• Hypochloremic hypokalemic metabolic alkalosis.
• Hypochloremia is due to the loss of hydrochloric acid with the repeating vomiting of stomach acid.
• Hypokalemia is due the kidneys exchanging potassium for protons to attempt to compensate.

Differential Diagnosis

• Gastroenteritis
• Gastroesophageal reflux
• Over-feeding
• Sepsis
• Urinary tract infection
• Food allergy

Treatment

• Stopping oral feeds.
• Insertion of nasogastric tube.
• Proper fluid resuscitation and correction of electrolyte derangements and base deficit (all derangements must be corrected prior to surgery).
• Ramstedt pyloromyotomy remains the standard procedure of choice.
• Infants can resume feeding after 6 hours.

Complications

• 1-2% of infants experience restenosis.
• Incomplete myotomy.
• Bleeding.
• Perforation.