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Hypertrophic Pyloric Stenosis


Jaime Belkind-Gerson

, MD, MSc, University of Colorado

Reviewed/Revised Sep 2023

Hypertrophic pyloric stenosis is obstruction of the pyloric lumen due to pyloric muscular hypertrophy. Diagnosis is by abdominal ultrasonography. Treatment is surgical.

Hypertrophic pyloric stenosis may cause almost complete gastric outlet obstruction. It affects a few out of 1000 infants and is more common among males by about a 5:1 ratio, particularly firstborn males. It occurs most often between 3 weeks and 6 weeks of age and rarely after 12 weeks.

Etiology of Hypertrophic Pyloric Stenosis

The exact etiology of hypertrophic pyloric stenosis is uncertain, but a genetic component is likely because siblings and offspring of affected people are at increased risk, particularly monozygotic twins. Maternal smoking during pregnancy also increases risk. Proposed mechanisms include lack of neuronal nitric oxide synthase, abnormal innervation of the muscular layer, and hypergastrinemia.

Infants exposed to certain macrolide antibiotics (eg, erythromycin) in the first few weeks of life are at significantly increased risk.

Etiology references

Symptoms and Signs of Hypertrophic Pyloric Stenosis

Symptoms of hypertrophic pyloric stenosis typically develop between 3 weeks and 6 weeks of life. Forceful vomiting, often described as "projectile" vomiting (without bile), occurs shortly after eating. Until dehydration sets in, children feed avidly and otherwise appear well, unlike many of those with vomiting caused by systemic illness.

Gastric peristaltic waves may be visible, crossing the epigastrium from left to right. A discrete, 2- to 3-cm, firm, movable, and olive-like pyloric mass is sometimes palpable deep in the right side of the epigastrium.

Diagnosis of Hypertrophic Pyloric Stenosis

  • Ultrasonography

Hypertrophic pyloric stenosis should be suspected in all infants in the first several months of life with projectile vomiting, particularly if they have an appetite and otherwise appear well.

Diagnosis of hypertrophic pyloric stenosis is by abdominal ultrasonography showing increased thickness of the pylorus (typically to 4 mm; normal, < 3 mm) along with an elongated pylorus (> 16 mm).

Pearls & Pitfalls

  • Hypertrophic pyloric stenosis should be suspected in all infants in the first several months of life with projectile vomiting, particularly if they have an appetite and otherwise appear well.

If the diagnosis remains uncertain, ultrasonography can be repeated serially or an upper gastrointestinal series can be done, which typically shows delayed gastric emptying and a string sign or railroad track sign of a markedly narrowed, elongated pyloric lumen. In rare cases, upper endoscopy is required for confirmation.

Treatment of Hypertrophic Pyloric Stenosis

  • Surgery (pyloromyotomy)

Initial treatment of hypertrophic pyloric stenosis is directed at hydration and correcting electrolyte abnormalities.

Definitive treatment is a longitudinal pyloromyotomy, which leaves the mucosa intact and separates the incised muscle fibers. Postoperatively, the infant usually tolerates feeding within a day.

Nonsurgical therapy is not considered a good alternative because of the efficacy and safety of pyloromyotomy.

Key Points

  • Projectile vomiting occurs shortly after feeding in an infant < 3 months old, usually between 3 weeks and 6 weeks of age, and, unless dehydration becomes significant, appetite tends to be intact and the infant appears well.

  • Diagnosis is by ultrasonography.

  • Treatment is surgical incision of the hypertrophied pyloric muscle.

Drugs Mentioned In This Article

Drug Name Select Trade
A/T/S, Akne-mycin, E.E.S., Emcin Clear , EMGEL, E-Mycin, ERYC, Erycette, Eryderm , Erygel, Erymax, EryPed, Ery-Tab, Erythra Derm , Erythrocin, Erythrocin Lactobionate, Erythrocin Stearate, Ilosone, Ilotycin, My-E, PCE, PCE Dispertab , Romycin, Staticin, T-Stat
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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