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) 
- Sex: ♂ > ♀ (∼ 5:1)
- More common in firstborn children
- The incidence is higher in white populations. 
Epidemiological data refers to the US, unless otherwise specified.
- Environmental factors
- Genetic factors: patients with affected relatives have a higher risk of hypertrophic pyloric stenosis
- Macrolide antibiotics
- Symptoms usually develop between the 2nd and 7th week of age (rarely after the 12th 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
- Initial imaging: abdominal ultrasound shows an elongated and thickened pylorus
- Alternative imaging
- Hypochloremic, hypokalemic metabolic alkalosis, a classic result, is now uncommon because infants are typically diagnosed and treated early.
- Hyponatremia or hypernatremia may be present.
|Differential diagnosis of newborn vomiting|
|Hypertrophic pyloric stenosis|
|Midgut volvulus and intestinal malrotation|
|Benign gastroesophageal reflux|| |
|Gastroesophageal reflux disease|
|Congenital adrenal hyperplasia with salt loss|
|Cyclical vomiting syndrome || |
Benign gastroesophageal reflux (GER) 
- Etiology: temporary insufficiency of the lower esophageal sphincter
- Regurgitation and/or vomiting of food shortly after feeds
- Overall healthy appearance, normal development, no weight loss
- Diagnostics: clinical diagnosis
- 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
- Definition: GER associated with persistent symptoms and complications
- Etiology: persistent insufficiency of the lower esophageal sphincter
- Clinical features
- Diagnostics: mainly a clinical diagnosis; imaging can be indicated if symptoms after initiation of empirical treatment persist
Cyclical vomiting syndrome
- Etiology: unknown; a family history with migraines is common
- Epidemiology: peak incidence in children 3–7 years of age
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 
- ≥ 3 episodes of acute vomiting in the past year
- Each episode lasting < 1 week
- Asymptomatic intervals between episodes
- Avoid possible triggers (e.g., foods such as cheese or chocolate; stress)
- Prophylactic treatment
- Supportive care (e.g., IV fluids)
Sandifer syndrome 
- 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
- Diagnosis: a clinical diagnosis; association with GERD and normal neurological examination
- Treatment: Resolves with effective treatment of GERD
The differential diagnoses listed here are not exhaustive.
- Very good prognosis
- Mortality rate: < 1%