Practice Essentials
Pyloric stenosis, also known as infantile hypertrophic pyloric stenosis (IHPS), is the most common cause of intestinal obstruction in infancy. IHPS occurs secondary to hypertrophy and hyperplasia of the muscular layers of the pylorus, causing a functional gastric outlet obstruction.
In 1717, Blair first reported autopsy findings of pyloric stenosis. Although the description of the signs and symptoms of infantile hypertrophic pyloric stenosis can be found in the 17th century, the clinical picture and pathology were not accurately described until 1887 by the Danish pediatrician, Hirschsprung. Prior to 1912, early successful surgical procedures included gastroenterostomy, pyloroplasty, and forcible dilatation via gastrostomy. In 1912, Ramstedt observed an uneventful recovery in a patient following pyloroplasty, where sutures used in reapproximating the seromuscular layer had disrupted. Following this observation, he began leaving the split muscle layer unsutured in all subsequent repairs. The Ramstedt pyloromyotomy remains the standard procedure for pyloric stenosis today.
According to Pandya and Heiss, current recommendations include ultrasonography for diagnosis, preoperative corrections of electrolytes, and use of surgical techniques.[1]
Pathophysiology
Marked hypertrophy and hyperplasia of the 2 (circular and longitudinal) muscular layers of the pylorus occurs, leading to narrowing of the gastric antrum. The pyloric canal becomes lengthened, and the whole pylorus becomes thickened. The mucosa is usually edematous and thickened. In advanced cases, the stomach becomes markedly dilated in response to near-complete obstruction.
The causes of infantile hypertrophic pyloric stenosis are multifactorial.[2] Both environmental factors and hereditary factors are believed to be contributory. Possible etiologic factors include deficiency of nitric oxide synthase containing neurons, abnormal myenteric plexus innervation, infantile hypergastrinemia, exposure to macrolide antibiotics, lack of exposure to vasoactive intestinal peptide in breast milk, and hypersensitivity to motilin.
A meta-analysis that investigated perinatal factors associated with hypertrophic pyloric stenosis onset and reported that first-born (OR 1.19, 95% CI: 1.07-1.33), cesarean section delivery (OR 1.63, 95% CI: 1.53-1.73), preterm birth (OR 1.37, 95% CI: 1.12-1.67), and bottle-feeding (OR 2.46, 95% CI: 1.76-3.43), were associated with the hypertrophic pyloric stenosis onset with bottle-feeding as the most significant risk factor.[3, 4]
A cohort study found that treatment of young infants with macrolide antibiotics was strongly associated with infantile hypertrophic pyloric stenosis (IHPS).[5] A meta-analysis of 9 studies reaffirmed a significant association of postnatal exposure of erythromycin and the development of pyloric stenosis. This association is strongest if the exposure occurred in the first 2 weeks of life, although persists to a lesser degree in children between 2 and 6 weeks of age.[6, 7, 8] Maternal use of macrolides during the first 2 weeks after birth was also associated with an increased risk of IHPS.[5]
Nitric oxide has been demonstrated as a major inhibitory nonadrenergic, noncholinergic neurotransmitter in the GI tract, causing relaxation of smooth muscle of the myenteric plexus upon its release. Impairment of this neuronal nitric oxide synthase (nNOS) synthesis has been implicated in infantile hypertrophic pyloric stenosis, in addition to achalasia, diabetic gastroparesis, and Hirschsprung disease.
Another study reported the possibility that low serum lipids could be a risk factor for IHPS. Further studies are needed to determine the significance of these findings.[9]
Rogers has suggested, that persisting duodenal hyperacidity, due to a high parietal cell mass (PCM) and loss of gastrin control, produces pyloric stenosis from repeated pyloric contraction in response to hyperacidity.[10]
No specific pattern of inheritance exists, although there is likely a genetic component to IHPS development. It is more common in first-born white males of northern European ancestry and occurs more frequently in monozygotic than dizygotic twins. Children of affected parents are also affected at a higher rate (as high as 7%).
A nationwide study of nearly 2 million Danish children born between 1977 and 2008 shows strong evidence for familial aggregation and heritability of pyloric stenosis. Results of the study found a heritability rate of 87% in affected families, lending to the idea that familial aggregation may be explained by shared genes that affect responses to postnatal factors in causing pyloric stenosis.[11]
Epidemiology
United States
The incidence of infantile hypertrophic pyloric stenosis is 2-4 per 1000 live births.
Mortality/Morbidity
Death from infantile hypertrophic pyloric stenosis is rare and unexpected. The reported mortality rate is very low and usually results from delays in diagnosis with eventual dehydration and shock.
Race
Infantile hypertrophic pyloric stenosis is more common in whites than Hispanics, blacks, or Asians. The incidence is 2.4 per 1000 live births in whites, 1.8 in Hispanics, 0.7 in blacks, and 0.6 in Asians. It is also less common amongst children of mixed race parents.
Sex
Infantile hypertrophic pyloric stenosis has a male-to-female predominance of 4-5:1, with 30% of patients with infantile hypertrophic pyloric stenosis being first-born males.
Age
The usual age of presentation is approximately 2 – 6 weeks of life. Approximately 95% of infantile hypertrophic pyloric stenosis cases are diagnosed in those aged 3-12 weeks. Infantile hypertrophic pyloric stenosis is rare in premature infants. In addition, premature infants have a delayed diagnosis secondary to low birth weight and atypical presentation.
Further Inpatient Care
The infant with pyloric stenosis should continue to receive intravenous fluid until feeding is resumed. Feeding can be initiated 4-8 hours after recovery from anesthesia, although earlier feeding has been studied. Infants who are fed earlier than 4 hours do not have a worse total clinical outcome; however, they do vomit more frequently and more severely, leading to significant discomfort for the patient and anxiety for the parents.
As many as 80% of patients continue to regurgitate after surgery; however, patients who continue to vomit 5 days after surgery may warrant further radiologic investigation.
Patients should be observed for surgical complications (eg, incomplete pyloromyotomy, mucosal perforation, bleeding) and may be discharged home when adequately hydrated and tolerating feedings well.
A study from the Children's Hospital of Philadelphia showed that a standardized feeding regimen had no advantage over ad libitum feedings.[21]
Complications
In the patient that presents with vomiting and has a missed/delayed diagnosis of pyloric stenosis, there is risk of significant dehydration leading to hypovolemic shock.
Author
Sathyaseelan Subramaniam, MD, FAAP, Chief Fellow in Pediatric Emergency Medicine, Kings County Hospital, State University of New York Downstate Medical Center
Disclosure: Nothing to disclose.
Coauthor(s)
Jennifer H Chao, MD, FAAP, Clinical Associate Professor of Pediatric Emergency Medicine, State University of New York Downstate College of Medicine; Attending Physician, Pediatric Emergency Department, Kings County Hospital and University Hospital Brooklyn
Disclosure: Nothing to disclose.
Richard H Sinert, DO, Professor of Emergency Medicine, Clinical Assistant Professor of Medicine, Research Director, State University of New York College of Medicine; Consulting Staff, Vice-Chair in Charge of Research, Department of Emergency Medicine, Kings County Hospital Center
Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Pfizer Pharmaceutical<br/>Received research grant from: National Institutes Health.
Specialty Editors
Mary L Windle, PharmD, Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
Grace M Young, MD, Associate Professor, Department of Pediatrics, University of Maryland Medical Center
Disclosure: Nothing to disclose.
Chief Editor
Kirsten A Bechtel, MD, Associate Professor of Pediatrics, Section of Pediatric Emergency Medicine, Yale University School of Medicine; Co-Director, Injury Free Coalition for Kids, Yale-New Haven Children's Hospital
Disclosure: Nothing to disclose.
Additional Contributors
Garry Wilkes, MBBS, FACEM, Director of Clinical Training (Simulation), Fiona Stanley Hospital; Clinical Associate Professor, University of Western Australia; Adjunct Associate Professor, Edith Cowan University, Western Australia
Disclosure: Nothing to disclose.
Jagvir Singh, MD, Director, Division of Pediatric Emergency Medicine, Lutheran General Hospital of Park Ridge
Disclosure: Nothing to disclose.
Acknowledgements
Dara A Kass, MD Clinical Assistant Instructor, Department of Emergency Medicine, State University of New York Downstate Medical Center, Kings County Hospital
Dara A Kass, MD is a member of the following medical societies: American College of Emergency Physicians, Emergency Medicine Residents Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
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