Assessment of Causes of Nausea 🤢

Nausea is a complex symptom mediated by the vomiting centre in the medulla, integrating signals from the gastrointestinal tract (via the vagus nerve), the chemoreceptor trigger zone (CTZ), vestibular system, and higher cortical centres. The key clinical task is distinguishing benign self-limiting causes from surgical, metabolic, or neurological emergencies.

🩺 1. Clinical History

1. ⏱️ Onset & Duration:
   • Acute (hours–days) → infection, obstruction, DKA, raised ICP
   • Chronic/intermittent → GERD, migraine, pregnancy, medication effect
2. 🍽️ Pattern & Timing:
   • Post-prandial → gastritis, PUD, obstruction
   • Early morning → pregnancy, alcohol use, raised ICP
   • Motion-related → vestibular cause
3. 🤒 Associated Symptoms:
   • Vomiting (bilious? projectile? blood?)
   • Abdominal pain (colicky → obstruction; epigastric → PUD/pancreatitis)
   • Headache or visual disturbance → raised ICP
   • Polyuria, polydipsia → DKA
   • Fever → infection
4. 🥗 Dietary History: Food poisoning risk, alcohol intake.
5. 📚 Medical History:
   • GI disease (GERD, ulcer, IBD)
   • Neurological (migraine, tumour, head injury)
   • Endocrine/metabolic (diabetes, thyroid disease, adrenal insufficiency)
   • Pregnancy possibility in women of childbearing age
6. 💊 Medication Review:
   • NSAIDs, antibiotics
   • Opioids
   • Metformin
   • Chemotherapy
   • SSRIs
7. 🌍 Lifestyle & Exposure: Alcohol, recreational drugs, recent travel, sick contacts.

🔎 2. Physical Examination

1. 👀 General: Dehydration (dry mucosa, reduced skin turgor), pallor, jaundice.
2. 📈 Vitals: Fever (infection), tachycardia (dehydration), hypotension (shock), hypertension + bradycardia (raised ICP).
3. 🫃 Abdominal Exam:
   • Tenderness (localized → appendicitis, cholecystitis)
   • Guarding/rigidity → peritonitis
   • Distension + tinkling bowel sounds → obstruction
4. 🧠 Neurological Exam: Focal deficits, papilloedema, nystagmus.
5. 👂 ENT: Vestibular signs if vertigo present.

🧪 3. Investigations

1. Blood Tests:
   • FBC (infection, anaemia)
   • U&E (dehydration, electrolyte imbalance)
   • LFTs (hepatobiliary cause)
   • Amylase/lipase (pancreatitis)
   • Glucose + ketones (DKA)
   • TFTs if thyroid disease suspected
2. 🤰 Pregnancy Test: Essential in women of reproductive age.
3. 🖥️ Imaging:
   • Ultrasound (gallstones, obstruction)
   • CT abdomen if obstruction or intra-abdominal pathology suspected
   • CT/MRI brain if raised ICP suspected
4. 🦠 Stool Tests: If infectious diarrhoea suspected.

🚨 Red Flags

• Projectile vomiting (raised ICP)
• Bilious vomiting (obstruction)
• Haematemesis
• Severe abdominal pain with guarding
• Weight loss or persistent vomiting >2–3 weeks

📚 Common Causes of Nausea

• 🫃 Gastrointestinal: GERD, gastritis, PUD, gastroenteritis, obstruction, pancreatitis, biliary disease.
• 🧠 Neurological: Migraine, vestibular disorders, raised ICP.
• ⚖️ Metabolic/Endocrine: DKA, uraemia, thyroid dysfunction, electrolyte disturbance.
• 🤰 Pregnancy: Morning sickness, hyperemesis gravidarum.
• 💊 Drug-induced: NSAIDs, opioids, antibiotics, chemotherapy.
• 🧘 Psychogenic: Anxiety, stress-related functional nausea.

💊 4. Management Principles

1. 🩹 Treat Underlying Cause:
   • PPI for GERD/PUD
   • Fluids + insulin for DKA
   • Antibiotics if indicated
2. 💧 Rehydration: Oral rehydration salts or IV fluids if severe.
3. 💊 Antiemetics (based on mechanism):
   • Metoclopramide (dopamine antagonist; prokinetic)
   • Ondansetron (5-HT3 antagonist)
   • Cyclizine (antihistamine; vestibular causes)
   • Prochlorperazine (dopamine antagonist)
4. 🥗 Lifestyle Advice: Small frequent meals, avoid triggers, reduce alcohol.
5. 🔁 Follow-Up: Persistent or unexplained nausea requires further evaluation.

📊 Summary Table

⚖️ Always think physiologically: nausea arises from gut irritation, vestibular disturbance, metabolic toxins, raised intracranial pressure, or cortical input. Identifying the dominant pathway helps guide rational antiemetic choice.