Synopsis
Distinguish progressive non-bilious gastric-outlet vomiting from bilious intestinal obstruction in early infancy, correct physiological derangement and secure time-critical imaging and paediatric surgical care.
- Clarify colour and force: pyloric stenosis causes progressive projectile non-bilious milk vomiting; malrotation or distal obstruction causes dark-green bilious vomiting.
- Pyloric stenosis usually presents around 2 to 8 weeks with hunger after vomiting, poor weight gain, reduced urine and sometimes visible gastric peristalsis or an epigastric olive.
- First-line test for suspected pyloric stenosis is expert ultrasound; repeat or specialist review is appropriate when early measurements are equivocal but the clinical trajectory persists.
- Check glucose, blood gas, sodium, potassium, chloride, bicarbonate, urea and creatinine; hypochloraemic hypokalaemic alkalosis supports prolonged gastric loss.
- Pyloric stenosis is a medical stabilisation before surgical correction: stop feeds, rehydrate and correct chloride and potassium before pyloromyotomy.
- Bilious vomiting is a paediatric surgical emergency: nil by mouth, nasogastric decompression, IV fluids and immediate surgical contact.
- For a stable child with suspected malrotation, an upper gastrointestinal contrast study is the reference anatomical test in many UK pathways; ultrasound may help but must not delay surgery in an unstable child.
- Do not diagnose reflux, feed intolerance or gastroenteritis from vomiting alone when bile, distension, blood, shock or focal abdominal signs are present.
Key red flags
Dark-green bilious vomit at any age requires urgent obstruction assessment and is not a reflux symptom.
Abdominal distension, tenderness, bloody stool, shock or metabolic acidosis suggests bowel ischaemia or perforation.
Progressively projectile non-bilious vomiting at 2 to 8 weeks with hunger and weight loss suggests hypertrophic pyloric stenosis.
Lethargy, reduced urine, prolonged capillary refill or a sunken fontanelle indicates dehydration needing hospital correction.
Fever, altered consciousness, bulging fontanelle or abnormal neurological examination broadens vomiting to sepsis or intracranial disease.
A normal abdominal radiograph or initial ultrasound cannot safely exclude malrotation when bilious vomiting persists.
Investigation priorities
Measure muscle thickness and channel length and observe gastric passage without radiation.
Management branches
A young infant has progressive forceful milk vomiting with hunger or weight loss.
- Assess hydration, weight and glucose and obtain electrolytes and blood gas.
- Request urgent expert pyloric ultrasound and repeat assessment if early findings are equivocal.
- Stop feeds and correct volume, chloride and potassium under paediatric surgical care.
- Proceed to definitive pyloromyotomy after full physiological optimisation.