Infantile (hypertrophic) pyloric stenosis
A concise, exam‑focused guide for emergency clinicians.
Overview
Infantile hypertrophic pyloric stenosis (HPS) is an acquired hypertrophy of the gastric pyloric circular muscle producing progressive gastric outlet obstruction. It is a surgical condition presenting classically in early infancy with recurrent, non‑bilious projectile vomiting and a characteristic metabolic disturbance.
Definitive treatment is pyloromyotomy. The emergency clinician’s role is recognition, resuscitation, diagnostic confirmation and timely paediatric surgical referral.
Epidemiology and risk factors
- Incidence ≈ 4 per 1,000 live births.
- Male:female ratio ≈ 4:1.
- 10-15% have a positive family history; more common in first‑born infants.
- Reported associations: bottle feeding and caesarean delivery.
- Drug exposure: neonatal macrolide exposure (especially erythromycin in the first 2 weeks of life) increases risk; document medication history and follow local reporting requirements (MHRA advisory).
- Typical age at presentation: most present between 3 and 12 weeks; presentations may occur up to ~4 months.
Pathophysiology
- Progressive idiopathic hypertrophy of the pyloric circular muscle leads to narrowing of the gastric outlet.
- Recurrent non‑bilious, forceful (projectile) vomiting causes loss of gastric HCl, producing a hypochloraemic metabolic alkalosis and often hypokalaemia.