Pyloric stenosis
Progressive hypertrophy of the pyloric muscle narrows the gastric outlet until only forceful contraction can empty the stomach, so the vomiting is projectile and non-bile-stained, and the electrolyte picture is a direct consequence of losing acidic gastric contents rather than the obstruction itself.
In a nutshell
Hypertrophy of the pyloric muscle progressively narrows the gastric outlet, so the stomach must generate excessive pressure to empty, producing forceful, non-bile-stained projectile vomiting in a hungry infant. Loss of acidic, potassium-rich gastric contents plus renal compensation for dehydration produces a hypochloraemic, hypokalaemic metabolic alkalosis. Fluids correct the metabolic derangement first; pyloromyotomy is curative but never urgent.
Classic presentation
A 3–6 week old first-born male infant with forceful projectile non-bile-stained vomiting after feeds, remaining hungry afterwards, with weight loss and a palpable olive-shaped mass on test feed.
Key points
- Vomiting is always non-bilious because the obstruction is proximal to the duodenum, where bile enters the gut: bile-stained vomiting points elsewhere.
Educational content pending clinical review. Not medical advice.