• Though possible in the adult population through acquired causes such as malignancy, hypertrophic pyloric stenosis is a congenital disorder of infants characterized by progressive gastric outlet obstruction.
• This is a surgical disease with eventual consequences to the growth and electrolyte balance of the newborn. Unrecognized the natural history is to progress rather than recede and the infant will become sicker through time.
• The clinical starting point is a neonate typically <12 weeks old presenting with non-bilious vomiting post-prandially who may be entirely well appearing or dehydrated with metabolic derangements depending on the delay in seeking care.
• The end point for these patients is referral and transfer to pediatric general surgery typically following ultrasonography confirmed diagnosis.

• The historical presentation is classically found with:
  • Male infant predominance, 3-6 weeks old (0 – 12 weeks)
  • Forceful “projectile” non-bilious, non-bloody vomiting that occurs shortly after feeding
  • Infants remain “hungry and vomiting” unlike with many other etiologies for vomiting
  • Without other symptoms of illness or infection, commonly otherwise “well” per parents given earlier presentations in general now seen on a population level
  • Strongly familial, though not required
• The physical exam is poorly sensitive to make the diagnosis:
  • The historical “olive-shaped RUQ mass” is poorly sensitive (27%) and reflects a historical diagnostic era of more delayed presentations
  • Assess for dehydration (skin, heart rate, level of consciousness, urine output, etc.)
  • Assess for alternate etiologies for the source of vomiting
    • Head trauma, ingestions, infections, etc.
•  Lab findings may guide treatment for unwell infants in whom bloodwork is drawn:
  • Hypochloremic metabolic alkalosis in delayed presentations
  • Hypo or hyponatremia may be present
  • Severe liver enzyme and conjugated bilirubin derangements or markers of infection should prompt investigation for alternate etiologies of vomiting
• Formal ultrasonography is both highly sensitive and specific in diagnosing hypertrophic pyloric stenosis and is the diagnostic test of choice for infants in whom this is suspected.
  • Pylorus dimensional criteria is beyond the scope of the ED clinician
  • Classically the “target” or “donut” sign is seen in cross-sectional view
  • Abdominal x-ray is poorly sensitive and specific in making this diagnosis
• Pitfalls in the work-up of pyloric stenosis include:
  • Failing to consider diagnostically outside of classic age ranges, as it is recognized to occur any time after birth until approximately 12 weeks.
  • Failure to consider diagnostically due to patients being seen earlier in the natural history of this disease and may be well appearing without worrisome physical exam findings.
  • Failure to recognize operator-dependence of ultrasound in the exceptional sensitivity and specificity found in modern studies (99.5% and 100% respectively). If the patient is unwell, consider admission and repeat ultrasound in one week if alternate explanations for vomiting are not found.

Treatment for hypertrophic pyloric stenosis involves three major components:

1. Hydration
2. Electrolyte repletion
3. Pediatric general surgery referral and transfer

Specific dosing for hydration and electrolyte repletion will be specific to the derangements seen, which as described are extremely heterogeneous based on how early the patient presents.

For hydration consider resuscitative crystalloid and maintenance fluid with dextrose. For electrolyte repletion use serial metabolic panels to adjust fluid regimens and consult with pediatric colleagues as these patients will require admission prior to transfer.

The majority of these infants will present in well condition without dehydration or electrolyte derangements. Definitive management is surgical.

• Following diagnosis, all patients should be referred and transferred for definitive care in discussion with the accepting pediatric general surgery team.
• For unwell infants, admission to the presenting hospital prior to transfer may be required primarily for resuscitation and electrolyte correction in anticipation of future surgical management.

• All patients will require transfer to a pediatric general surgery referral center for definitive management. The timing of transfer is influenced by clinical status and in discussion of operative timing with the accepting physician.
• Resuscitation and correction of electrolyte derangements for the unwell infant are paramount prior to transfer. In well children, the accepting general surgeon will provide guidance regarding timeline for transfer.

1. Pyloric stenosis – Radiopaedia.org

   
   

2. Infantile hypertrophic pyloric stenosis – UpToDate.com

   
   

3. The Pediatric Surgical Abdomen – The Pediatric Playbook Podcast

   
   

1. Aspelund G, Langer JC. Current management of hypertrophic pyloric stenosis. Semin Pediatr Surg. 2007 Feb;16(1):27-33. doi: 10.1053/j.sempedsurg.2006.10.004. PMID: 17210480.\

   
   

2. Kapoor R, Kancherla V, Cao Y, et al. Prevalence and descriptive epidemiology of infantile hypertrophic pyloric stenosis in the United States: A multistate, population-based retrospective study, 1999-2010. Birth Defects Res. 2019;111(3):159-169. doi:10.1002/bdr2.1439

   
   

3. Papadakis K, Chen EA, Luks FI, Lessin MS, Wesselhoeft CW Jr, DeLuca FG. The changing presentation of pyloric stenosis. Am J Emerg Med. 1999 Jan;17(1):67-9. doi: 10.1016/s0735-6757(99)90020-7. PMID: 9928704.

   
   

4. Poon TS, Zhang AL, Cartmill T, Cass DT. Changing patterns of diagnosis and treatment of infantile hypertrophic pyloric stenosis: a clinical audit of 303 patients. J Pediatr Surg. 1996 Dec;31(12):1611-5. doi: 10.1016/s0022-3468(96)90032-9. PMID: 8986971.

   
   

5. St Peter SD, Holcomb GW 3rd, Calkins CM, Murphy JP, Andrews WS, Sharp RJ, Snyder CL, Ostlie DJ. Open versus laparoscopic pyloromyotomy for pyloric stenosis: a prospective, randomized trial. Ann Surg. 2006 Sep;244(3):363-70. doi: 10.1097/01.sla.0000234647.03466.27. PMID: 16926562; PMCID: PMC1856534.