Hypertrophic pyloric stenosis

Hypertrophic pyloric stenosis, the most common cause of gastric outlet obstruction in infants, is characterized by hypertrophy and hyperplasia of the pyloric sphincter in the first months of life. Clinical manifestations usually appear between three and five weeks of age. The primary symptom is regurgitation progressing to nonbilious, projectile vomiting, which occurs intermittently or after feeding. The infant is irritable and demonstrates a strong rooting and sucking reflex because of hunger. Constant vomiting leads to hypokalemic and hypochloremic metabolic alkalosis. The diagnosis is usually clinical and involves the detection of a palpable, olive-shaped structure in the epigastrium (a sign of marked hypertrophy of the pylorus) and visible gastric peristalsis proximal to the site of obstruction. The condition may also be diagnosed on ultrasound in the absence of a palpable, olive-shaped structure. Initial management involves adequate rehydration and correction of electrolyte imbalances. The definitive treatment is Ramstedt pyloromyotomy.

• Incidence: 0.5–5:1000 live births (considered to be the most common cause of gastric outlet obstruction in infants) ^[1]
• Sex: ♂ > ♀ (∼ 5:1)
• More common in firstborn children
• The incidence is higher in white populations. ^[2]

Epidemiological data refers to the US, unless otherwise specified.

• Environmental factors
  • Exposure to nicotine during pregnancy ^[2]
  • Bottle feeding ^[3]
• Genetic factors: patients with affected relatives have a higher risk of hypertrophic pyloric stenosis
• Macrolide antibiotics
  • Erythromycin and azithromycin are associated with a higher risk of hypertrophic pyloric stenosis, especially when administered within 2 weeks after birth
  • Hypertrophic pyloric stenosis associated with macrolide antibiotics should be reported to the FDA

• Symptoms usually develop between the 2^nd and 7^th week of age (rarely after the 12^th week).
• Frequent regurgitation progressing to projectile, nonbilious vomiting immediately after feeding
• An enlarged, thickened, olive-shaped, nontender pylorus (diameter of 1–2 cm) should be palpable in the epigastrium
• A peristaltic wave, moving from left to right, may be evident in the epigastrium
• "Hungry vomiter": demands re-feeding after vomiting, demonstrates a strong rooting and sucking reflex, irritable
• If left untreated: dehydration, weight loss, failure to thrive

• Initial imaging: abdominal ultrasound shows an elongated and thickened pylorus
• Alternative imaging
  • Barium studies
    • Narrow pyloric orifice
    • String sign: elongated, thickened pylorus
    • Beak sign: The pylorus is only partially open to the stomach because of hypertrophy, resulting in two muscular layers adjacent to one another in an "open beak."
  • Endoscopy
• Laboratory tests
  • Hypochloremic, hypokalemic metabolic alkalosis, a classic result, is now uncommon because infants are typically diagnosed and treated early.
    • The loss of gastric hydrochloric acid from emesis results in increased bicarbonate and decreased chloride concentrations in the blood. (See pathophysiology of acid-base disorders for more information.)
    • Hypokalemia usually occurs in infants that have been vomiting for many days or even weeks.
  • Hyponatremia or hypernatremia may be present.

Nowadays, hypertrophic pyloric stenosis is diagnosed early, and infants generally do not present with significant electrolyte imbalances.

Gastroesophageal reflux in infants ^[5][6]

• Definition: the movement of stomach contents into the esophagus with or without spitting up and regurgitation due to transient lower esophageal sphincter relaxation
• Epidemiology: physiologic process in infants, typically occurs shortly after feeding
• Etiology
  • Esophageal sphincter: transient lower relaxation due to frequent, large volume feedings
  • Esophagus: short length and/or supine position
• Clinical features
  • Spitting up or regurgitation shortly after feeding
  • Normal physical examination and development (normal weight gain, no difficulty feeding)
• Diagnostics: clinical findings
• Management
  • Reassurance of the infant's parents
  • Conservative measures
    • Maintain breastfeeding
    • Avoiding overfeeding
    • Positioning therapy
      • Maintain the infant in an upright position for 20–30 minutes after feeding
      • Avoid sitting
    • Using food thickeners
    • Avoid exposure to tobacco smoke ^[7]
• Prognosis: : the frequency of episodes decreases with age, usually resolves spontaneously by 12–18 months of age

Gastroesophageal reflux disease (GERD) ^[5]

See “Gastroesophageal reflux disease in infants.”

Cyclical vomiting syndrome ^[4][8]

• Etiology: : unknown, often associated with stress (e.g., psychological stress due to parent divorce, infections, fasting) and a personal or family history of migraine headaches
• Epidemiology: peak incidence 5 years of age ^[8]
• Clinical features
  • Recurrent, self-limited attacks of severe vomiting (bilious or nonbilious) and no evidence of anatomical anomalies or underlying conditions
  • Attacks may be accompanied by severe nausea, headaches, photophobia, abdominal pain
• Diagnostic criteria (Rome IV criteria for cyclical vomiting syndrome): All four criteria must be fulfilled for the diagnosis of cyclical vomiting syndrome to be made ^[4]
  • Each episode lasting < 1 week
  • ≥ 3 episodes in the past year and ≥ 2 episodes in the past six months, occurring ≥ 1 week apart
  • Asymptomatic intervals between episodes (mild symptoms may be present)
  • Onset ≥ 6 months prior and symptoms have to present for the past 3 months
• Treatment ^[8]
  • Identify and avoid triggers (e.g., foods such as cheese or chocolate, stress)
  • Prophylactic treatment
    • Cyproheptadine in patients < 5 years old
    • Amitriptyline in patients > 5 years old
  • Supportive care (e.g., IV fluids, antiemetics)

Sandifer syndrome ^[9]

• Definition: a paroxysmal movement disorder characterized by torticollis and arching of the spine that occurs in association with gastroesophageal reflux disease (GERD) and hiatal hernia.
• Epidemiology
  • Unknown incidence and prevalence
  • Associated with GERD in children
• Clinical features
  • Torticollis and arching of the spine (opisthotonic posturing), lasting between 1– 3 minutes, and often associated with ingestion of food
  • Vomiting, poor feeding, epigastric discomfort
• Diagnosis: based on clinical findings (association with GERD and a normal neurological examination)
• Treatment: treatment of GERD

The differential diagnoses listed here are not exhaustive.

• Conservative measures: before surgery
  • Correct electrolyte imbalance (e.g., replace K⁺)
  • IV rehydration
  • Frequent administration of small meals (12–24 per day)
  • Elevate head
• Treatment of choice: : Ramstedt pyloromyotomy (a longitudinal muscle-splitting incision of the hypertrophic sphincter)

• Very good prognosis
• Mortality rate: < 1% ^[10]