> Table of Contents > Pyloric Stenosis
Pyloric Stenosis
Joshua Scott Will, DO
Jennifer M. Cornwell, DO
Rachel M. Jones, DO
image BASICS
  • Progressive narrowing of the pyloric canal, occurring in infancy
  • Synonym(s): infantile hypertrophic pyloric stenosis (IHPS)
  • Predominant age: infancy
    • Onset usually at 3 to 6 weeks of age; rarely in the newborn period or as late as 5 months of age
  • Considered the most common condition requiring surgical intervention in the 1st year of life
  • A recent decline in its incidence has been reported in a number of countries.
  • Predominant sex: male > female (4 to 5:1)
In Caucasian population, 2 to 5:1,000 babies; less common in African American and Asian populations
National prevalence level is 1 to 2:1,000 infants, ranging from 0.5 to 4.21:1,000 live births.
  • Abnormal relaxation of the pyloric muscles leads to hypertrophy.
  • Redundant mucosa fills the pyloric canal.
  • Gastric outflow is obstructed, leading to gastric distension and vomiting.
  • The exact cause remains unknown, but multiple genetic and environmental factors have been implicated (1,2)[B].
  • Breast versus bottle feeding—increased vasoactive intestinal peptide in breast milk may mediate pyloric relaxation and increase gastric emptying while bottle feeding may cause higher serum levels associated with pylorospasm (3)[C].
Recent studies have identified linkage to chromosome 11 and multiple loci and chromosome 16 (1,2)[B].
  • Incidence higher in firstborn Caucasian boys (lower incidence in African Americans and Asians)
  • 5 times increased risk with affected first-degree relative
  • Strong familial aggregation and >80% heritability
  • Multiple gestation—200 fold increased risk if monozygotic twin diagnosed and 20 fold increased risk if dizygotic twin diagnosed
  • Breast feeding protective versus bottle feeding risk increased
  • Postnatal macrolide use (i.e., erythromycin, azithromycin)—erythromycin agonist of motilin which might cause continuous contraction of the pyloric muscle (2)[B],(3)[C]
  • A recent surveillance study of a population-based birth defects registry identified association between pyloric stenosis and the use of fluoxetine in the 1st trimester, even after adjustment for maternal age and smoking. The adjusted odds ratio was 9.8 (95% CI 1.5-62) (4)[B].
Associated anomalies present in ˜4-7% of infants with pyloric stenosis.
  • Hiatal and inguinal hernias (most commonly)
  • Other anomalies include the following:
    • Congenital heart disease
    • Esophageal atresia
    • Tracheoesophageal fistula
    • Renal abnormalities
    • Turner syndrome and trisomy 18
    • Cornelia de Lange syndrome
    • Smith-Lemli-Opitz syndrome
  • A common proposed genetic link between breast cancer, endometriosis, and pyloric stenosis has been observed in families.
  • Firm, mobile (“olivelike”) mass palpable in the right upper quadrant (historically 70-90% of the time)
  • However, this finding has decreased in occurence to about 13% due to earlier diagnosis with US (3)[C]
  • Epigastric distention
  • Visible gastric peristalsis after feeding
  • Late signs: dehydration, weight loss
  • Rarely, jaundice when starvation leads to decreased glucuronyl transferase activity resulting in indirect hyperbilirubinemia
  • Inexperienced or inappropriate feeding
  • GERD
  • Gastritis
  • Congenital adrenal hyperplasia, salt-losing
  • Pylorospasm
  • Gastric volvulus
  • Antral or gastric web
Metabolic disturbances are late findings and are uncommon in present era of early diagnosis and intervention.
  • If prolonged vomiting, then check electrolytes for the following:
    • Hypokalemia
    • Hypochloremia
    • Metabolic alkalosis
  • Elevated unconjugated bilirubin level (rare)
  • Paradoxical aciduria: The kidney tubules excrete hydrogen to preserve potassium in face of hypokalemic alkalosis.
  • Abdominal US is the study of choice.
    • US shows thickened and elongated pyloric muscle and redundant mucosa.
  • Upper GI series reveals strong gastric contractions; elongated, narrow pyloric canal (string sign); and parallel lines of barium in the narrow channel (double-tract sign or railroad track sign).
Test Interpretation
Concentric hypertrophy of pyloric muscle

  • Ramstedt pyloromyotomy is curative. The entire length of hypertrophied muscle is divided, with preservation of the underlying mucosa.
  • Surgical approaches include open (traditional right upper quadrant transverse) incision, more contemporary circumumbilical incision, and laparoscopic techniques.
  • A recent review concluded that the laparoscopic approach results in less postoperative pain and can be performed with no increase in operative time or complications (5)[A].
  • Conservative approach
    • Conservative management of infantile hypertrophic pyloric stenosis with atropine can be effective in approximately six out of seven cases but has a lower success rate and longer duration of therapy than surgery (6)[B].
    • Atropine therapy may be considered as an alternative to pyloromyotomy for patients unsuitable or at high risk for surgery and in areas of the world where surgery on small infants is unavailable or unsafe (6)[B].
Admission Criteria/Initial Stabilization
  • Prompt treatment to avoid dehydration and malnutrition
  • Correct acid-base and electrolyte disturbances. Surgery should be delayed until alkalosis is corrected.
  • Patients need pre- and postop apnea monitoring. They have a tendency toward apnea to compensate with respiratory acidosis for their metabolic alkalosis.
IV Fluids
To correct dehydration and metabolic abnormalities. For optimal resusication in infants, use D5 1/2NS with 20 meq of KCl (3)[C].
Patient Monitoring
  • Routine pediatric health maintenance
  • Postoperative monitoring, including monitoring for pain, emesis, apnea
  • If significant emesis present after 1 to 2 weeks, then upper GI studies needed to rule out incomplete pyloromyotomy or duodenal leak (3)[C]
  • No preoperative feeding
  • Initiate feeding 4 hours after surgery with adlib feedings thereafter (7)[A].
Surgery is curative.
1. Feenstra B, Geller F, Carstensen L, et al. Plasma lipids, genetic variants near APOA1, and the risk of infantile hypertrophic pyloric stenosis. JAMA. 2013;310(7):714-721.
2. Krogh C, Fischer TK, Skotte L, et al. Familial aggregation and heritability of pyloric stenosis. JAMA. 2010;303(23):2393-2399.
3. Peters B, Oomen MW, Bakx R, et al. Advances in infantile hypertrophic pyloric stenosis. Expert Rev Gastroenterol Hepatol. 2014;8(5):533-541.
4. Bakker MK, De Walle HE, Wilffert B, et al. Fluoxetine and infantile hypertrophic pylorus stenosis: a signal from a birth defects-drug exposure surveillance study. Pharmacoepidemiol Drug Saf. 2010;19(8):808-813.
5. Oomen MW, Hoekstra LT, Bakx R, et al. Open versus laparoscopic pyloromyotomy for hypertrophic pyloric stenosis: a systematic review and meta-analysis focusing on major complications. Surg Endosc. 2012;26(8):2104-2110.
6. Mercer AE, Phillips R. Question 2: can a conservative approach to the treatment of hypertophic pyloric stenosis with atropine be considered a real alternative to surgical pyloromyotomy? Arch Dis Child. 2013;98(6):474-477.
7. Graham KA, Laituri CA, Markel TA, et al. A review of postoperative feeding regimens in infantile hypertrophic pyloric stenosis. J Pediatr Surg. 2013;48(10):2175-2179.
Additional Reading
  • Ein SH, Masiakos PT, Ein A. The ins and outs of pyloromyotomy: what we have learned in 35 years. Pediatr Surg Int. 2014;30(5):467-480.
  • Everett KV, Capon F, Georgoula C, et al. Linkage of monogenic infantile hypertrophic pyloric stenosis to chromosome 16q24. Eur J Hum Genet. 2008;16(9):1151-1154.
  • Everett KV, Chioza BA, Georgoula C, et al. Genomewide high-density SNP-based linkage analysis of infantile hypertrophic pyloric stenosis identifies loci on chromosomes 11q14-q22 and Xq23. Am J Hum Genet. 2008;82(3):756-762.
  • Georgoula C, Gardiner M. Pyloric stenosis a 100 years after Ramstedt. Arch Dis Child. 2012;97(8):741-745.
  • National Birth Defects Prevention Network. Selected birth defects data from population-based birth defects surveillance programs in the United States, 2003-2007. Birth Defects Res A Clin Mol Teratol. 2010;88(12):1062-1174.
  • Owen RP, Almond SL, Humphrey GM. Atropine sulphate: rescue therapy for pyloric stenosis [published online ahead of print August 2, 2012]. BMJ Case Rep.
  • Sommerfield T, Chalmers J, Youngson G, et al. The changing epidemiology of infantile hypertrophic pyloric stenosis in Scotland. Arch Dis Child. 2008;93(12):1007-1011.
  • Wyrick DL, Smith SD, Dassinger MS. Surgeon as educator: bedside ultrasound in hypertrophic pyloric stenosis. J Surg Educ. 2014;71(6):896-898.
Q40.0 Congenital hypertrophic pyloric stenosis
Clinical Pearls
  • Pyloric stenosis is the most common condition requiring surgical intervention in the 1st year of life.
  • The condition classically presents between 1 and 5 months of life, with projectile vomiting after feeds and a firm, mobile mass in the right upper quadrant.
  • Abdominal US is the study of choice.
  • Surgery (laparoscopic Ramstedt pyloromyotomy is the preferred method) is curative.