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

References:^[2][3]

Epidemiological data refers to the US, unless otherwise specified.

• Environmental factors
  • Exposure to nicotine during pregnancy
  • Bottle feeding
• 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

References:^[3][4][5]

• 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”, non-tender 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

References:^[2][5]

• Initial imaging: abdominal ultrasound → shows an elongated and thickened pylorus
• Alternative imaging: if ultrasound is inconclusive
  • 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 with an "open beak."
  • Endoscopy
• Laboratory tests
  • Hypochloremic, hypokalemic metabolic alkalosis is a classic result, but now uncommon as the infants are more commonly 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 do not generally present with significant electrolyte imbalances!

References:^[2][5][6]

Differential diagnosis of newborn vomiting
Condition	Findings
Hypertrophic pyloric stenosis	Regurgitation Projectile, nonbilious vomiting No diarrhea Alkalosis and hypokalemia
Midgut volvulus and intestinal malrotation	Bilious vomiting Abdominal distension Signs of bowel ischemia: hematochezia, hematemesis, hypotension, and tachycardia in severe cases
Benign gastroesophageal reflux	Regurgitation and/or vomiting of food shortly after feeding Healthy children with normal development
Gastroesophageal reflux disease	Regurgitation and/or vomiting of food shortly after feeding Poor appetite, weight loss, failure to thrive Abdominal pain/discomfort Wheezing, stridor, chronic cough, hoarseness
Gastroenteritis	Diarrhea Vomiting Possibly fever
Congenital adrenal hyperplasia with salt loss	Vomiting, apathy, weight loss Acidosis and hyperkalemia
Cyclical vomiting syndrome [7]	≥ 3 episodes of acute vomiting in the past year; each episode lasting < 1 week; asymptomatic intervals between episodes.

Benign gastroesophageal reflux (GER)

• Etiology: temporary insufficiency of the lower esophageal sphincter
• Clinical features
  • Regurgitation and/or vomiting of food shortly after feeds
  • Overall healthy appearance, normal development, no weight loss
• Diagnostics: clinical diagnosis
• Treatment
  • Positioning therapy: maintain upright position after feeding, avoid sitting or supine position
  • Thickening of food
• Prognosis: very good; resolves spontaneously in the majority of cases by approx. 18 months of age

Gastroesophageal reflux disease (GERD)

• Definition: GER associated with persistent symptoms and complications
• Etiology: persistent insufficiency of the lower esophageal sphincter
• Clinical features
  • Regurgitation, vomiting
  • Poor appetite, refusal to feed, weight loss, failure to thrive
  • Abdominal pain/discomfort
  • Crying and irritability
  • Wheezing, stridor, hoarseness, chronic cough
• Diagnostics: mainly a clinical diagnosis; imaging can be indicated if symptoms after initiation of empirical treatment persist
• Treatment
  1. Conservative measures: positioning therapy and thickening of food (see “Treatment” section of GER above)
  2. Pharmacological treatment: H₂-receptor blockers (e.g., ranitidine) and PPIs

Cyclical vomiting syndrome

• Etiology: unknown; a family history with migraines is common
• Epidemiology: peak incidence in children 3–7 years of age
• Presentation
  • Recurrent attacks of severe vomiting; (bilious or non-bilious) with a typical pattern and no evidence of anatomical anomalies
  • Attacks can be accompanied by severe nausea, headaches, photophobia, abdominal pain
• Diagnostic criteria (Rome III criteria for cyclical vomiting syndrome): All three criteria need to be fulfilled for the diagnosis of cyclical vomiting syndrome to be made ^[7][8]
  • ≥ 3 episodes of acute vomiting in the past year
  • Each episode lasting < 1 week
  • Asymptomatic intervals between episodes
• Treatment
  • Avoid possible triggers (e.g., foods such as cheese or chocolate; stress)
  • Prophylactic treatment
  • Supportive care (e.g., IV fluids)

References:^[8][9]

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)

References:^[2][5]