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.
- 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, 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
- 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|
|Congenital adrenal hyperplasia with salt loss|
|Cyclical vomiting syndrome |
Gastroesophageal reflux in infants 
- 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
- Spitting up or regurgitation shortly after feeding
- Normal physical examination and development (normal weight gain, no difficulty feeding)
- Diagnostics: clinical findings
- Prognosis: : the frequency of episodes decreases with age, usually resolves spontaneously by 12–18 months of age
Cyclical vomiting syndrome 
- 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 
- Clinical features
Diagnostic criteria ( ): All four criteria must be fulfilled for the diagnosis of cyclical vomiting syndrome to be made 
- 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 
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.
- Clinical features
- Diagnosis: based on clinical findings (association with GERD and a normal neurological examination)
The differential diagnoses listed here are not exhaustive.
- Very good prognosis
- Mortality rate: < 1%