Nausea / Vomiting

Nausea and vomiting have a wide variety of causes. Acute gastroenteritis is the most common cause across all age groups; in children, viral infection, acute otitis media, and UTIs are also common. Vomiting should be distinguished from regurgitation — the effortless return of gastric contents without nausea or forceful abdominal muscle contraction, seen with achalasia, rumination syndrome, or a Zenker diverticulum — since the two point toward different workups.

Diagnostic pearls

• Surgical causes are unlikely without abdominal pain.
• Vomiting without bile staining — pyloric obstruction.
• Vomiting of bile — obstruction below the duodenal ampulla.
• Vomiting of ingested food — oesophageal obstruction.
• Vomiting without nausea — raised intracranial pressure.
• Forceful vomiting from any cause can produce petechiae on the upper torso and face that can look like meningococcaemia — the distinguishing feature is how unwell the patient otherwise looks: meningococcaemia patients are usually very sick, while vomiting-related petechiae often occur in someone who otherwise looks reasonably well.

Diagnostic strategy — adults

Probability diagnosis: gastroenteritis; drugs/alcohol; motion sickness; pregnancy; migraine; GORD.

Serious causes: bowel obstruction; severe infection (meningitis, acute viral hepatitis); malignancy; appendicitis; pancreatitis/biliary colic; acute MI.

Other: gastroparesis; achalasia; ileus; glaucoma; cyclic vomiting syndrome (discrete attacks of vomiting or nausea at varying intervals with normal health between episodes, most common in childhood but recognised in adults — cannabinoid hyperemesis syndrome is a cyclic-vomiting mimic in chronic cannabis users, relieved by a hot bath and by stopping cannabis).

Red flags: pallor; signs of hypovolaemia (hypotension/tachycardia); peritoneal signs; headache/stiff neck/confusion; distended abdomen.

Complications of vomiting itself, independent of the underlying cause: dehydration and electrolyte disturbance (typically a hypokalaemic metabolic alkalosis); oesophageal tear, partial (Mallory-Weiss) or complete (Boerhaave syndrome); aspiration pneumonia if vomitus is inhaled in a patient who is unconscious or only partly conscious; and, with chronic vomiting, undernutrition and weight loss.

Diagnostic strategy — infants

Probability diagnosis: feeding problems; food intolerance; physiological (possetting); GORD; viral infections.

Must not miss: oesophageal atresia; congenital pyloric stenosis (projectile vomiting in weeks 3–6 of life, failure to thrive); intussusception; malrotation/volvulus; meconium ileus; small bowel atresia.

Red flags: excessive drooling of frothy secretions; bile-stained vomitus (malrotation/volvulus); delayed passage of meconium (>24 hours); inguinal hernias; inability to tolerate orals at all — i.e. vomiting of the first feed (oesophageal atresia); failure to thrive.

Diagnostic strategy — children

Probability diagnosis: gastroenteritis; other viral/common infections; motion sickness; migraine/cyclical vomiting.

Must not miss/severe: appendicitis; strangulated inguinal hernia; raised ICP (e.g. from head injury); serious infection (meningitis, pneumonia, diabetic ketoacidosis); haemolytic uraemic syndrome; binging/purging.

Broader differential for recurrent or atypical childhood vomiting (i.e. once the acute-gastroenteritis-type causes above have been excluded) — roughly ordered common to very rare:

• Gastrointestinal: coeliac disease (common, ~1% prevalence — reduced appetite, fatigue/irritability, poor growth, iron deficiency anaemia); eosinophilic oesophagitis (uncommon — dysphagia, atopy, food refusal, food bolus impaction); inflammatory bowel disease (uncommon — abdominal pain, diarrhoea ± blood, weight loss/growth failure); Helicobacter pylori-associated peptic ulcer disease (epigastric pain, iron deficiency — common in Aboriginal and Torres Strait Islander children and migrants from developing countries); post-viral gastroparesis (early satiety, postprandial epigastric pain after a recent infection); symptomatic intestinal malrotation/volvulus (rare — bilious vomiting, epigastric distension, can present non-specifically in older children); superior mesenteric artery syndrome (rare — sudden weight loss, recurrent postprandial vomiting and abdominal pain).
• Metabolic/endocrine: type 1 diabetes (uncommon — weight loss, polyuria, polydipsia, dehydration, lethargy); inborn errors of metabolism (rare — vomiting induced by prolonged fasting or protein loading, neurological symptoms); adrenal insufficiency (rare — hypoglycaemia, hyperpigmentation, salt craving); hereditary fructose intolerance (very rare — vomiting specifically after fruit or lollies).
• Neuropsychiatric: cyclical vomiting syndrome (common — stereotypical episodes each resembling the last, often a family history of migraine); space-occupying lesion (very rare — early-morning vomiting, headache, visual disturbance, nystagmus); Panayiotopoulos syndrome, an early-onset benign childhood occipital epilepsy (rare — triad of nocturnal seizures, tonic eye deviation, and vomiting).

First-line work-up for this broader differential: finger-prick glucose; full blood count, electrolytes, fasting glucose, LFTs, CRP, amylase, lipase, iron studies and coeliac serology; urine and stool microscopy, culture and sensitivity; abdominal ultrasound if the differential suggests it. Urgent brain MRI and paediatric referral if a space-occupying lesion is suspected.

Management

This page is a diagnostic-strategy reference; management is condition- specific (see the relevant page — e.g. gastroenteritis, migraine, GORD). One point worth flagging here because it changes ED-avoidance calculus directly: for children with gastroenteritis-related vomiting who have failed oral rehydration, a single oral dose of ondansetron increases the proportion who stop vomiting and reduces both the rate of immediate hospital admission and the need for IV rehydration, at the cost of more frequent diarrhoea as a side effect — evidence from emergency-department settings rather than primary care, but relevant to a GP’s threshold for ED referral versus a trial of oral rehydration first.