Diagnosing Pyloric Stenosis in Newborns
The most reliable signs of pyloric stenosis in newborns include projectile non-bilious vomiting, palpable olive-shaped mass in the epigastrium, and visible peristaltic waves across the abdomen. 1
Clinical Presentation
Key Symptoms
- Projectile non-bilious vomiting: The hallmark symptom, typically occurring after feeds
- Progressive worsening: Vomiting becomes more forceful and frequent over time
- Hungry after vomiting: Infants typically want to feed again immediately after vomiting
Key Physical Findings
- Palpable "olive": A firm, mobile, olive-shaped mass in the right upper quadrant or epigastrium (classic finding)
- Visible peristaltic waves: Moving from left to right across the upper abdomen
- Signs of dehydration: Decreased skin turgor, dry mucous membranes, sunken fontanelles
- Failure to thrive: Weight loss or poor weight gain
Timing and Demographics
- Typically presents between 2-8 weeks of age
- More common in male infants (5.7:1 male to female ratio) 2
- Family history may be present
Metabolic Abnormalities
- Hypochloremic, hypokalemic metabolic alkalosis (due to loss of gastric acid)
- Paradoxical aciduria (kidneys retain H+ to compensate for alkalosis)
Diagnostic Algorithm
Clinical suspicion based on history and physical exam:
- Non-bilious projectile vomiting in 2-8 week old infant
- Attempt to palpate the pyloric "olive" (best done during feeding when stomach is relaxed)
If "olive" is palpable:
- Diagnosis is confirmed clinically
- Proceed to preoperative preparation
If "olive" is not palpable but clinical suspicion remains high:
- Obtain ultrasound of the pylorus
- Diagnostic criteria: Pyloric muscle thickness >3mm, pyloric channel length >14mm
If ultrasound is equivocal:
- Consider upper GI series (shows "string sign" or elongated pyloric channel)
- In rare cases, endoscopy may be used to visualize the narrowed pyloric channel 3
Differential Diagnosis
- Gastroesophageal reflux
- Gastroenteritis
- Formula intolerance
- Malrotation with or without volvulus (presents with bilious vomiting)
- Pylorospasm (intermittent functional obstruction)
Important Considerations
- Pyloric stenosis is not a surgical emergency but requires prompt diagnosis and appropriate preoperative management 4, 2
- Fluid and electrolyte abnormalities must be corrected before surgical intervention
- Erythromycin use in neonates has been associated with increased risk of pyloric stenosis 1
- Bilious vomiting suggests a different diagnosis (e.g., malrotation with volvulus) which may require urgent intervention 1, 5
Pitfalls to Avoid
- Mistaking for simple reflux: Pyloric stenosis vomiting is more forceful and progressive
- Missing the diagnosis: Can lead to severe dehydration and metabolic derangements
- Rushing to surgery: Metabolic abnormalities must be corrected preoperatively
- Overlooking bilious vomiting: This suggests intestinal obstruction distal to the ampulla of Vater, not pyloric stenosis 1
- Failing to monitor fluid balance: Document vomiting episodes and assess hydration status 1
Remember that pyloric stenosis is a medical condition requiring surgical correction, but the preoperative stabilization of the infant is crucial for successful outcomes.