Atlas of pathophysiology, 2 Edition

Part II - Disorders

Gastrointestinal Disorders

Pyloric Stenosis

Pyloric stenosis is a narrowing of the pylorus—the outlet from the stomach to the small intestine. The incidence of pyloric stenosis is approximately 2 to 3 of every 1,000 infants.

Age Alert

Pyloric stenosis primarily occurs in infants. It occurs more commonly in boys than in girls and is rare in patients older than age 6 months.


Unknown, possibly related to genetic factors


Pyloric stenosis is caused by hypertrophy and hyperplasia of the circular and longitudinal muscles of the pylorus. When the sphincter muscles thicken, they become inelastic and this leads to a narrowing of the opening. The pyloric canal becomes lengthened and the whole pylorus becomes thickened. The mucosa usually is edematous and thickened. The extra peristaltic effort needed to empty stomach contents into the small intestine leads to hypertrophied muscle layers of the stomach.

Signs and symptoms

·   Vomiting, mild initially and then becoming projectile

·   In infants: appearing hungry most of the time

·   Diarrhea

·   Dehydration (poor skin turgor, depressed fontanels, dry mucous membranes, decreased tearing)

·   Failure to gain weight or weight loss

·   Dyspepsia

·   Abdominal pain

·   Abdominal distension

·   Visible gastric peristalsis

·   Firm, nontender, and mobile 1 to 2 cm hard mass, known as an olive, present in the midepigastrium to the right of midline; best palpated after the infant has vomited and when calm

·   Diminished stools

·   Lethargy

Diagnostic test results

·   Barium X-ray reveals a distended stomach and narrowed and elongated pylorus.

·   Ultrasound shows thickened muscles of the pylorus.

·   Chemistry panel often reveals hypochloremia, hypokalemia, and metabolic alkalosis. Hypernatremia or hyponatremia may also be present.


·   I.V. fluids

·   Correction of electrolyte abnormalities

·   Surgery

·   Nothing by mouth before surgery; small frequent feedings after surgery




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