Frequent cause of vomiting in early infancy. Maximum occurrence from the end of the first month to the beginning of the second month of life; mainly in boys.

1. If ignored hypertrophic pyloric stenosis may lead to a dangerous exsiccosis or a failure to thrive.
2. Hypertrophic pyloric stenosis may be treated successfully with a simple operation.

Unknown.

Hypertrophy of the pyloric muscle of the stomach which becomes clinically manifest to a different degree and during the first three months at a different time.

History and findings: Vomiting shortly after ingestion, which develops very fast or gradually to the typical clinical picture: Projectile vomiting during every feeding or shortly thereafter. Frowning due to spasms of the stomach. Development of signs of exsiccosis as standing wrinkles, of diarrhea (so-called starvation stools) and arrest of increase of weight and loss of weight as sign of failure to thrive. Clinical skills:
1. A feed with sweet tea shows peristaltic waves crossing from the left to the right in the upper abdomen.
2. Palpation of a pyloric tumor like an olive slightly to the right of the umbilicus corresponding to the hypertrophic pylorus.

Possible are
a) death following exsiccosis and failure to thrive and
b) spontaneous recovery following many weeks with vomiting and insufficient possibility of feeding.

The differential diagnosis includes all causes of vomiting, regurgitation and dysphagia because the three symptoms cannot be well differentiated from each other in infancy. In case of clinical manifestation in the newborn the differential diagnosis of an obstructive ileus has to be considered, and in case of coffee-ground appearance due to a gastritis or esophagitis the other causes leading to hematemesis as for instance gastroesophageal reflux. The latter is in case of vomiting one of the main differential diagnoses of hypertrophic pyloric stenosis.

1. Serumanalysis for fluid and electrolyte abnormalities. Clinical assessment of the degree of exsiccation (weight prior and at the beginning of the disease and at hospitalization and signs of exsiccosis).
2. Ultrasound for determination of the precise thickness of the pyloric muscle and of the length of the pyloric channel.
3. In case of doubtful values or for exclusion of a gastroesophageal reflux or of another type of gastric outlet stenosis (gastric empting disorder, antral or pyloric atresia or stenosis) a gastroesophagography is necessary.
4. In case of progression of initially not severe vomiting repeated ultrasound because the radiological findings may not be present at the beginning of the disease.

Prior pyloromyotomy the electrolyte and fluid imbalance should be corrected because the postoperative course is then uneventful and the operation is not emergent.

Total recovery including a secondary gastroesophageal reflux. In case of persistent vomiting an incomplete pyloromyotomy, a combination with a primary reflux or a rare cause has to be considered.