About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Vomiting + severe headache or papilloedema = image the brain
- The differential diagnosis table is the centrepiece: prioritize emergency causes before common benign causes
- Initial investigations should be targeted to physiology, pregnancy status when relevant, organ pattern and Canadian practice pathways
- Management depends on severity: resuscitate unstable patients, treat reversible causes and involve specialists early when red flags are present
- For MCCQE1, focus on the next best step, CanMEDS communication/safety-netting and Canadian rather than US/UK guideline patterns
Approach to the Presentation
Nausea & Vomiting is assessed as a clinical presentation rather than as a named diagnosis. The first task is to identify instability, red flags and immediately reversible threats. Then classify the syndrome by timing, associated symptoms, examination findings and dominant organ pattern. In Canadian MCCQE1-style questions, the safest pathway is usually to stabilize first, rule out must-not-miss causes, use targeted investigations rather than shotgun testing, and give clear follow-up and safety-net advice.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Bowel Obstruction | must-not-miss | Vomiting with colicky pain, distension, obstipation, previous surgery or hernia | CT abdomen/pelvis with contrast |
| Raised Intracranial Pressure / CNS Lesion | must-not-miss | Morning/projectile vomiting, headache worse lying/coughing, papilloedema, focal neurological signs | Urgent CT head or MRI |
| Diabetic Ketoacidosis / Hyperosmolar Crisis | must-not-miss | Vomiting, abdominal pain, polyuria, polydipsia, Kussmaul breathing, diabetes or SGLT2 inhibitor | Capillary glucose, blood ketones, venous gas, electrolytes |
| Pregnancy / Hyperemesis Gravidarum | must-not-miss | Early pregnancy vomiting with dehydration, weight loss, ketonuria or electrolyte disturbance | beta-hCG, electrolytes, ketones; ultrasound if ectopic/molar concern |
| Acute Surgical Abdomen | must-not-miss | Vomiting with focal pain, fever, peritonism or RUQ/RLQ/epigastric localization | Targeted labs + ultrasound or CT |
| Acute Coronary Syndrome | must-not-miss | Nausea/vomiting with epigastric discomfort, diaphoresis, dyspnoea, diabetes or cardiac risks | ECG + serial troponin |
| Gastroenteritis / Foodborne Illness | common | Acute vomiting with diarrhoea, cramps, exposures or outbreak | Clinical; stool testing if severe/bloody/persistent/outbreak |
| Medication / Toxin Effect | common | Temporal relationship to opioids, antibiotics, digoxin, iron, NSAIDs, metformin, GLP-1 agonists, chemotherapy, alcohol | Medication review; targeted levels where relevant |
| Cannabis Hyperemesis Syndrome | common | Chronic cannabis use, cyclic vomiting, abdominal pain and hot showers | Clinical after excluding dangerous mimics |
| Vestibular Neuritis / Migraine | common | Prominent vertigo, motion sensitivity, nystagmus, ear symptoms or migraine features | Clinical; neuroimaging if central signs |
Red Flags & Key History
Symptoms
Bilious/faeculent vomiting, distension and obstipation — obstruction
Severe headache, morning vomiting, papilloedema or focal signs — raised ICP
Severe abdominal pain, peritonism, fever or shock
Pregnancy or possible pregnancy with vomiting and pain/bleeding
Polyuria, polydipsia, Kussmaul breathing or SGLT2 inhibitor use — DKA
Haematemesis or coffee-ground vomit — upper GI bleeding
Sick contacts or shared meal — infectious pattern
Signs
Orthostatic hypotension, dry mucosa, oliguria — volume depletion
Altered mental status or meningism
Abdominal distension with high-pitched/absent bowel sounds
Papilloedema or focal neurological deficit
Kussmaul respirations or ketotic breath
Approach to Investigation
First-line
Bedside testsCapillary glucose, ketones if diabetic/unwell, urine dip, beta-hCG when relevant, orthostatic vitals
Electrolytes, creatinine, venous gas/bicarbonateAssess dehydration, AKI, alkalosis/acidosis
CBC, liver enzymes, bilirubin, lipaseScreen infection, biliary disease, hepatitis, pancreatitis, bleeding
ECG +/- troponinOlder patients, diabetes, epigastric symptoms or cardiac risk
Second-line
CT abdomen/pelvisObstruction, perforation, appendicitis or severe unclear abdominal pain
Abdominal/RUQ ultrasoundBiliary symptoms, pregnancy-compatible imaging or urinary obstruction
CT head / MRI brainRaised ICP features, focal deficit, papilloedema or concerning headache
Stool testingSevere/persistent diarrhoea, blood, travel, immunocompromise or outbreak
Specialist
Upper endoscopyUpper GI bleeding, gastric outlet obstruction or persistent unexplained vomiting
Gastric emptying studySuspected gastroparesis after obstruction/metabolic causes excluded
Management Principles
MCC Vomiting/Nausea Objective + Canadian emergency and medication safety practice1
Supportive care
- Oral rehydration if mild; IV crystalloid if moderate/severe or unable to tolerate oral intake
- Correct potassium, magnesium, glucose and acid-base abnormalities
- Hold causative medications where safe
- Use antiemetics contextually while considering QT risk
2
Urgent pathways
- Obstruction: NPO, IV fluids, antiemetics, NG decompression if needed and surgical consultation
- DKA: insulin protocol, fluids, potassium and precipitant treatment
- Raised ICP: urgent neuroimaging/neurosurgical pathway
- Hyperemesis: hydration, thiamine before dextrose if prolonged, pregnancy-safe antiemetics
3
Gastroenteritis
- Oral rehydration and antiemetic if needed
- Avoid unnecessary antibiotics in uncomplicated viral gastroenteritis
- Safety-net dehydration, blood, persistent fever, severe pain or inability to keep fluids down
Complications & Pitfalls
- Missing extra-GI causes: raised ICP, DKA, adrenal crisis, pregnancy, sepsis and ACS.
- Dextrose before thiamine: prolonged malnutrition/alcohol use needs thiamine first.
- Overlooking electrolytes: vomiting may cause hypokalaemic alkalosis and arrhythmia.
MCCQE1 Exam Tips
- 1Vomiting + severe headache or papilloedema = image the brain
- 2Vomiting + distension + obstipation = obstruction pathway
- 3Reproductive-age patient: beta-hCG is first-line
- 4Cannabis hyperemesis: cannabis + cyclic vomiting + hot showers; cessation is definitive
- 5DKA can present with abdominal pain and vomiting
- 6Treat symptoms while investigating
practicetest your knowledge on nausea & vomitingApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — gastrointestinal and beyond.
open q-bank