Bilious vomiting (green bile) in a neonate or infant is a surgical emergency — malrotation with midgut volvulus causes complete intestinal ischaemia within 4–6 hours if untreated. It is incompatible with survival without emergency surgery. Never attribute bilious vomiting to feeding problems in neonates.
Pyloric stenosis peaks at 4–6 weeks (range 2–8 weeks), affects boys 4x more than girls, and presents with projectile non-bilious vomiting after feeds, a visibly hungry child (not ill), and hypochloraemic hypokalaemic metabolic alkalosis on bloods. The "olive" is palpable in only 50% of cases. US is confirmatory.
DKA in previously undiagnosed T1DM can present as a flu-like illness with vomiting. A urine dipstick (ketones ++) takes 30 seconds and should be performed in any vomiting child with polyuria, weight loss, or fatigue.
The timing and content of vomiting is the most important differentiating feature. "Redcurrant jelly" stool (bloodstained mucus) with colicky pain and vomiting in a 6–18 month old is intussusception until proven otherwise — this is a classic MRCGP and SCA scenario. Call 999 and document clearly.
Cyclical vomiting syndrome (CVS) is under-diagnosed — stereotyped episodes lasting 1–5 days with complete symptom-free periods between them, often triggered by stress or illness, frequently with a family history of migraine. Treating acute episodes with ondansetron (hospital) and preventing with amitriptyline or topiramate (specialist) is effective.
NICE CG84 dehydration assessment is validated in children and guides fluid management decisions. Skin turgor ("tenting") is less reliable in obese children. The most reliable bedside signs are: dry mucous membranes, sunken eyes, tachycardia, and reduced skin perfusion. Combining ≥3 signs improves diagnostic accuracy to >85%.
Blood pressure is a late sign of dehydration in children — children compensate well and can maintain normal BP until 25% blood volume loss. Tachycardia is an earlier and more sensitive marker. A normal BP does NOT rule out significant dehydration.
UTI causes vomiting as the primary presenting symptom in 40% of infants under 12 months — there are no localising urinary symptoms at this age. A dipstick takes 2 minutes. Missing UTI leads to pyelonephritis, bacteraemia, and renal scarring.
DKA is increasingly diagnosed in primary care as T1DM incidence rises. In new-onset T1DM, the presentation mimics gastroenteritis — vomiting, abdominal pain, and malaise. A BM and urine dipstick (ketones) in any child with unexplained vomiting + any of polyuria, weight loss, polydipsia or excessive tiredness detects DKA before the child deteriorates.
Point-of-care urine testing and blood glucose measurement are the two highest-yield investigations in primary care for vomiting children. Both take <3 minutes, change management, and detect serious diagnoses (UTI, DKA) that are commonly missed.
Stool culture for routine gastroenteritis has a very low yield and rarely changes management. NICE CG84 recommends restricting stool cultures to: bloody diarrhoea, suspected food poisoning outbreaks, travel-associated diarrhoea, immunosuppression, and failure to resolve after 7 days.
Intussusception has a classic presentation but also presents atypically — the "redcurrant jelly" stool is a late sign (<30% of cases). The classic presentation is: age 6–18 months, sudden-onset severe colicky pain, pallor, drawn-up legs, vomiting (initially non-bilious, may become bilious), followed by periods of apparent wellness between episodes. Any vomiting infant with unexplained pallor and inconsolable crying should be referred immediately.
ORS via syringe at 5ml every 1–2 minutes works even when children are actively vomiting because small volumes leave the stomach before the vomiting reflex is triggered. A Cochrane review (2006) found ORS as effective as IV rehydration for mild-moderate dehydration and associated with shorter hospital stays. Demonstrating the technique to parents in the surgery dramatically improves compliance.
Domperidone and metoclopramide are contraindicated in children due to extrapyramidal side effects (acute dystonic reactions). MHRA warnings (2014) restrict domperidone to adults only. Ondansetron is effective and safe but should be initiated in secondary care due to QT prolongation risk in children with electrolyte imbalances from dehydration.
The 48-hour exclusion rule is a public health measure based on viral shedding patterns — norovirus and rotavirus are maximally contagious during and immediately after illness. Returning to school before 48 hours causes secondary cases in classrooms. This is a legal requirement for food handlers and strongly recommended by PHE for children in communal settings.
Rotavirus vaccination has reduced childhood gastroenteritis hospitalisation by 70% since its introduction to the NHS schedule in 2013. It is the single most effective intervention for preventing severe rotavirus disease. Checking vaccination status during an acute consultation is a brief but valuable quality intervention.
Written safety-net advice reduces ED re-attendance by 40% in gastroenteritis (NICE evidence). Specific, actionable instructions ("call 999 if vomit turns green") are more effective than generic advice ("come back if worried"). Document that safety-netting was provided.
Gastroenteritis-triggered haemolytic uraemic syndrome (HUS) occurs 5–10 days after E. coli O157 infection — vomiting/diarrhoea resolves, then child develops pallor, reduced urine output, and bruising (microangiopathic haemolytic anaemia + renal failure). Parents should be warned about this specifically if bloody diarrhoea is present. Send stool culture and review in 1 week.