What is the appropriate treatment for a 2‑month‑old infant with recurrent projectile vomiting and ultrasound showing pyloric canal length 1.5 cm, muscle thickness 4 mm, and transverse diameter 1 cm (borderline hypertrophic pyloric stenosis)?

Management of Borderline Hypertrophic Pyloric Stenosis in a 2-Month-Old Infant

Given the recurrent projectile vomiting and borderline ultrasound measurements (pyloric muscle thickness 4 mm, length 1.5 cm, transverse diameter 1 cm), this infant should proceed directly to surgical pyloromyotomy after appropriate fluid resuscitation and electrolyte correction. 1, 2

Interpretation of Ultrasound Findings

Your ultrasound demonstrates borderline-to-positive findings for hypertrophic pyloric stenosis (HPS):

• Pyloric muscle thickness of 4 mm meets the diagnostic threshold (normal <3 mm; HPS typically >3-4 mm) 3
• Pyloric canal length of 1.5 cm (15 mm) is at the diagnostic cutoff (HPS typically >15-17 mm) 3
• The combination of recurrent projectile vomiting at 2 months of age with these measurements is diagnostic of HPS 1, 4

Clinical Context Supporting Surgical Intervention

The clinical presentation strongly supports HPS rather than benign gastroesophageal reflux:

• Projectile vomiting is the hallmark of pyloric stenosis, not typical GERD 1, 4
• Age of 2 months falls within the classic presentation window (2 weeks to 3 months) 5
• The vomiting is non-bilious, which is characteristic of HPS 1, 6

Preoperative Management

Before surgery, you must correct the metabolic derangements:

• Obtain electrolyte panel to assess for hypochloremic, hypokalemic metabolic alkalosis (classic finding in HPS from loss of gastric acid) 3, 2
• Provide IV fluid resuscitation with normal saline or lactated Ringer's solution 2, 4
• Add potassium chloride supplementation once urine output is established 2
• Surgery should be delayed until electrolytes normalize and the infant is adequately hydrated 2, 4

Definitive Treatment: Pyloromyotomy

Surgical pyloromyotomy remains the gold standard treatment:

• Pyloromyotomy (either open or laparoscopic) provides definitive cure with excellent outcomes 2, 4
• The procedure involves longitudinal incision of the hypertrophied pyloric muscle down to the submucosa 2, 4
• Success rate approaches 100% with minimal complications 4

Alternative Medical Management (Not Recommended in This Case)

While intravenous atropine therapy has been studied, it is not appropriate for your patient:

• Medical management with IV atropine requires prolonged hospitalization (median 13 days inpatient, followed by 44 days of oral atropine) 7
• Success rate is only 87%, meaning 13% still require surgery 7
• Given the clear clinical and radiographic findings, surgery provides faster resolution and shorter hospital stay 2, 4
• Atropine therapy should only be considered if families explicitly refuse surgery or if significant surgical contraindications exist 7

Common Pitfalls to Avoid

Do not mistake this for gastroesophageal reflux disease:

• GERD typically presents with non-forceful regurgitation and infants maintain weight gain 3
• The projectile nature of vomiting and borderline-positive ultrasound distinguish HPS from GERD 1, 4

Do not delay surgery waiting for "more definitive" measurements:

• Borderline measurements combined with classic clinical presentation warrant surgical intervention 1, 2
• Pyloric muscle hypertrophy is progressive; waiting may worsen metabolic derangements 6

Do not proceed to surgery without adequate resuscitation:

• Operating on a dehydrated, alkalotic infant increases anesthetic risk 2, 4
• Preoperative stabilization is essential to optimal outcome 1, 2

Postoperative Care

After pyloromyotomy, feeding can typically resume within hours:

• Most centers use ad lib feeding or graduated feeding protocols starting 4-6 hours postoperatively 4
• Some postoperative vomiting is common and does not indicate surgical failure 4
• Full feeds are usually achieved within 24-48 hours 2, 4