Nausea and Vomiting Diagnosis: Clinical Reasoning, Red Flags, and OSCE Approach

🤔 Are You Sure It’s Just the Stomach?

Are you quick to assume that vomiting is just a stomach problem? Think again.

Nausea and vomiting may seem like typical gastrointestinal symptoms, but they can also be signs of serious systemic diseases—such as intracranial pressure, myocardial infarction, or metabolic acidosis.

Whether you’re preparing for OSCEs or seeing patients in real-life clinical settings, what matters is not just asking “when did it start?”—but knowing what to ask, in what order, and when to worry about Red Flags.

In this article, we’ll walk through how to approach vomiting step-by-step: from history taking and physical examination to POCUS and lab tests—highlighting both common and critical causes you must not overlook.

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🧠 What You’ll Learn from This Article

• How to detect dangerous signs during history taking — Look beyond simple GI symptoms and consider neurological, cardiac, and metabolic causes of nausea and vomiting.
• How to narrow down the differential diagnosis using physical exam and POCUS — Identify key findings like abdominal distension, ileus, dehydration, or hyperemesis gravidarum at the bedside.
• How to think clinically before ordering tests — Recognize hidden culprits like EuDKA, reflux, or drug-induced vomiting before jumping into investigations or treatment.

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🧪 Case Introduction – A Patient’s Words

🚪 Doorway Information

• Age / Gender: 23-year-old woman
• Chief Complaint: Nausea and vomiting
• Vital Signs: BP 96/64 mmHg, HR 110/min, Temp 36.8°C, SpO₂ 99% (RA)

“Excuse me… I’ve been feeling nauseous for the past few days…
Even when I try to eat, I throw up right away. I can barely drink water…”

“Could this be… pregnancy? I don’t really think so, but I’m not sure.”

“I was scared to come to the hospital, but since yesterday, I’ve felt so dizzy just trying to stand up…”

This kind of presentation—how would you respond?

Let’s walk through this case starting from first impressions and build a structured approach.

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🔍 How to Think – First Impressions and Clinical Framework

Let’s begin our symptom-based clinical reasoning.

This is a case of a young woman with nausea and vomiting. Her vitals show hypotension and tachycardia — which already raises concern. While pregnancy or gastroenteritis might come to mind, we should not ignore the possibility of dehydration and systemic illness.

Let’s take a step back and organize the possible causes.

🧠 A Practical Framework for Nausea and Vomiting

Although vomiting is often associated with GI issues, the underlying causes can range from neurologic to metabolic, toxic, or psychiatric conditions. It’s helpful to think in four major categories:

1. Gastrointestinal Causes: Gastroenteritis, obstruction, cholecystitis, tumors
2. Central Nervous System Causes: Increased intracranial pressure, meningitis, subarachnoid hemorrhage
3. Metabolic Causes: DKA, uremia, hyperemesis gravidarum, medication-related
4. Psychogenic/Others: Eating disorders, myocardial infarction, vagal reflex

Now that we understand how broad the differential can be, let’s deepen our clinical reasoning using the Fact → Problem → Hypothesis framework.

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🧩 Clinical Reasoning with Fact / Problem / Hypothesis

📌 Fact (What we know)

• 23-year-old young woman
• Chief complaint: persistent nausea and vomiting for several days
• Unable to eat or drink properly
• Feels dizzy when standing up
• No clear menstrual history, but pregnancy not fully ruled out
• Vital signs: BP 96/64 mmHg, HR 110/min

📌 Problem (Clinical definition)

• Progressive and persistent vomiting (acute on subacute)
• Signs of dehydration with poor oral intake
• Pregnancy not excluded in a reproductive-age female

Reframing the symptoms this way helps us recognize the risk of missing serious underlying causes.

📌 Hypothesis (Differential diagnosis via VITAMIN CDE)

• Infectious: Viral or bacterial gastroenteritis
• Metabolic: Hyperemesis gravidarum, uremia, thyroid dysfunction
• Idiopathic/Psychiatric: Eating disorders, psychogenic vomiting
• Toxic: Medication-induced, food poisoning
• Autoimmune: Addison’s disease
• Neoplastic: GI or gynecologic tumors

Working hypotheses at this stage: Hyperemesis gravidarum, infectious gastroenteritis, and eating disorder

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🧠 Need to Know (NTK) – What to Ask Based on Hypotheses

Now that we have several working hypotheses, we need to gather key information to verify or rule them out.

🧪 Hypothesis	🔍 What You Need to Ask (NTK)
Hyperemesis gravidarum	– Last menstrual period (LMP) – Pregnancy test (urine hCG) – Pregnancy history, contraception, recent sexual activity – Weight loss, urine ketones
Infectious gastroenteritis	– Fever, abdominal pain, diarrhea – Similar symptoms in contacts (clustered cases) – History of raw food or recent travel – Stool characteristics (bloody, watery, etc.)
Eating disorder (bulimia type)	– Weight changes, dietary patterns, purging behaviors – Menstrual irregularities – Body image concerns, psychological stressors

In the next section, we’ll see how to gather this information using structured history-taking with OPQRST and PAM HITS FOSS.

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🗣 Step 1: History Taking – How to Uncover the Cause of Nausea and Vomiting

Simply asking “When did it start?” is not enough. Vomiting requires detailed and structured history-taking—focusing on the pattern, content, timing, associated symptoms, and patient background.

① OPQRST: Understanding the Pattern and Meaning

• O – Onset: “Was it sudden or gradual?” / “Is this your first time vomiting?”
• P – Provocation/Palliation: “Does anything make it better or worse?” / “Does it happen after eating or early in the morning?”
• Q – Quality: “What did you vomit?” / “Was there any unusual smell or color?” / “Any blood or bile?”
• R – Region/Radiation: “Any pain in the abdomen or chest?”
• S – Severity: “How often do you vomit per day?” / “Can you eat or drink at all?”
• T – Timing: “Does it occur at a specific time?” / “After meals or in the morning?”

📝 Tips: What the Vomit Tells You

• Greenish bile → possible duodenal involvement
• Bloody vomit → GI bleeding (e.g. ulcer, varices)
• Undigested food → gastric outlet obstruction or delayed emptying
• Projectile vomiting → increased intracranial pressure (especially in infants)
• Vomiting without nausea → intracranial matter (tumor, increased pressure)

② Look for Associated Symptoms

Nausea and vomiting can be linked to many other systems. Always ask about these:

• Fever, diarrhea → gastroenteritis, sepsis
• Headache, visual symptoms → CNS disorders like tumor or meningitis
• Upper abdominal pain → cholecystitis, pancreatitis, ulcers
• Weight loss → malignancy, endocrine disorders, eating disorders
• Fatigue, altered mental status → metabolic acidosis, uremia

📘 Column: Vagal Reflex and Nausea

Nausea is not always GI-related—it can also result from vagal stimulation. Be alert for bradycardia, sweating, cold extremities, and a pale appearance along with nausea.

③ PAM HITS FOSS: Don’t Forget the Background

• Past Medical History: diabetes, thyroid issues, renal failure, malignancy
• Allergy: foods, medications
• Medications: NSAIDs, antibiotics, SGLT2 inhibitors, antidepressants
• Hospitalization / Injury / Trauma / Surgery: post-op ileus, head trauma
• Family History: eating disorders, thyroid disorders
• OBGYN: pregnancy possibility, menstrual history
• Sexual History: contraception use, sexual activity
• Social History: alcohol, smoking, drug use, diet, stress, sleep patterns

These help distinguish between “typical vomiting” and Red Flag cases. Let’s now move on to physical exam.

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🩺 Step 2: Physical Examination – Don’t Miss These Red Flags

When a patient presents with vomiting, don’t just focus on the stomach. The cause may lie in the brain, heart, metabolic system, or elsewhere.

① General Impression and Vital Signs

• Tachycardia + Hypotension: Dehydration, bleeding, infection, Addison’s disease
• Fever: Gastroenteritis, cholecystitis, meningitis
• Level of consciousness, facial expression, posture: Consider CNS or metabolic disorders

First impressions matter—does the patient “look sick”?

② Head-to-Toe Examination

• Neurologic: Neck stiffness, cranial nerve palsies, papilledema, nystagmus → meningitis, brain tumor, increased ICP
• Cardiopulmonary: Irregular heartbeat, rales → AMI, heart failure-related vomiting
• Abdomen: Tenderness, guarding, tympanic sounds, bowel sounds → gastroenteritis, ileus, tumor
• Skin & Extremities: Signs of dehydration (dry skin, poor turgor), petechiae (suggesting DIC)

📘 Column: Smells and Sounds of Bowel Obstruction

Feculent-smelling vomit and high-pitched “tinkling” bowel sounds strongly suggest mechanical obstruction. Don’t underestimate the diagnostic power of your senses.

③ POCUS: Seeing the Cause of Vomiting

Target	Purpose	Possible Conditions
Stomach	Check for residual contents, delayed gastric emptying	Pyloric stenosis, gastroparesis, post-binge retention
Intestine	Distension, peristalsis	Ileus (mechanical or paralytic)
Pelvis	Check for pregnancy or gynecological causes	Ectopic pregnancy, ovarian tumor, hyperemesis
Gallbladder / Pancreas	Detect inflammation, stones, enlargement	Cholecystitis, pancreatitis

📝 Tips: Vomiting ≠ Always GI

Even if abdominal ultrasound is normal, consider the brain and heart. A full scan should include the epigastrium, lungs, and IVC/neck veins—think systemically.

📘 Column: Vomiting Without Nausea = Raised ICP?

“I didn’t feel nauseous… I just suddenly vomited.” Beware of vomiting without nausea—it may signal increased intracranial pressure (e.g., brain tumor, SAH).

• Projectile vomiting
• Vomiting + headache, visual changes, or altered mental status
• Neck stiffness, papilledema, abnormal eye movement

These should prompt urgent brain imaging (CT/MRI).

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🔬 Step 3: Tests and Imaging – Don’t Investigate Blindly

Do you routinely order “labs and abdominal CT” for vomiting without a clear purpose? Before ordering tests, define what you suspect and what you need to confirm.

① Select Tests Based on Your Hypothesis

🧪 Suspected Condition	🔍 Recommended Tests	🎯 Purpose
Hyperemesis gravidarum	Urine hCG, urine ketones, electrolytes, blood gas	Confirm pregnancy and assess for ketosis
Gastroenteritis	WBC, CRP, stool culture, stool appearance	Check for inflammation and infection
Cholecystitis, pancreatitis	Abdominal ultrasound, amylase/lipase, abdominal CT	Identify organic pathology
Eating disorder	Potassium, chloride, ECG (QT), blood gas	Evaluate for electrolyte disturbances from purging

📘 Column: EuDKA – The Danger of “Normal” Blood Sugar

Think DKA is ruled out because glucose is normal? Think again. SGLT2 inhibitors can cause euglycemic DKA (EuDKA).

• Suspect if: Vomiting + SGLT2 use + fatigue, acidotic signs
• Order: Urine/blood ketones, AG, pH, HCO₃⁻
• Key point: Blood glucose may be normal. Check pH!

② Use Imaging With a Clear Purpose

• Abdominal US: For cholecystitis, pancreatitis, tumors, gastric retention, ascites
• Abdominal CT: For obstruction, mass, abscess, perforation
• Head CT: For intracranial pathology (tumor, bleeding, meningitis suspicion)

Red Flag: Repetitive vomiting with no clear cause or vomiting without nausea should prompt head imaging.

📝 Tips to Avoid Unnecessary Testing

• Always hypothesize first—then test
• Skip early CT if GI cause is obvious and non-severe
• Strengthen your diagnosis with POCUS and physical exam—not just scans

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🔁 Case Reflection – Applying Step 1 to 3

Now that we’ve reviewed the step-by-step approach, let’s apply it to the opening case and see how clinical reasoning unfolds in real time.

🗣 Step 1: History Taking – Revisited

Doctor: “What brings you in today?”
Patient: “I’ve been feeling nauseous for the past few days. I throw up after eating and can’t even drink water…”

Doctor: “When did it start? Is this your first time experiencing this?”
Patient: “It started about three days ago. I’ve never had it last this long.”

Doctor: “Does it usually happen after meals? Any specific time of day?”
Patient: “I think I feel worse in the morning.”

Doctor: “Any raw or unusual food recently? Anyone around you with similar symptoms?”
Patient: “Not really…”

Doctor: “When was your last period?”
Patient: “Actually, I might be about a month late…”

Doctor: “Have you lost weight recently? How’s your appetite?”
Patient: “I haven’t been eating much… I think I’ve lost some weight.”

🧠 Summary

• Fact: Persistent nausea/vomiting for several days, worse in the morning, poor intake, possible menstrual delay
• Problem: Ongoing vomiting in a young woman with dehydration and pregnancy possibility
• Hypotheses: Hyperemesis gravidarum, eating disorder, infectious gastroenteritis (less likely)

🩺 Step 2: Physical Exam – Revisited

• Appearance: pale, dehydrated, sunken eyes, dry skin
• Vitals: BP 96/64 mmHg, HR 110/min → borderline shock
• Mental status: alert but slightly sluggish
• Abdomen: mild distension, no tenderness or guarding, hyperactive bowel sounds
• Neuro exam: normal, no headache or neck stiffness

These findings support volume depletion. Hyperemesis gravidarum becomes more likely, but we also need to rule out other metabolic causes (e.g., Addison’s, EuDKA).

🔬 Step 3: Tests and Imaging – Revisited

• Urine hCG: Positive → confirms pregnancy
• Urine ketones: Positive (moderate)
• Electrolytes: Na 130, K 3.4 (mild hyponatremia and hypokalemia)
• Blood gas: Mild metabolic acidosis, slightly elevated AG
• Abdominal ultrasound: Intrauterine pregnancy confirmed, no ascites

Conclusion: Diagnosed with hyperemesis gravidarum with dehydration and ketosis. Other causes (e.g., EuDKA, Addison’s) were considered but ruled out based on labs.

Initial management: IV fluids, antiemetics, and patient education on pregnancy care and warning signs.

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🏥 When to Refer – Red Flags and Pre-Referral Workup

Most cases of nausea and vomiting can be managed in primary care or outpatient settings. However, there are situations where specialist referral is crucial for patient safety and further evaluation.

📍 When to Refer

• Hyperemesis gravidarum with severe weight loss (>5%), electrolyte imbalance, or ketonuria → refer for inpatient care
• Suspected eating disorder requiring psychiatric intervention
• Recurrent vomiting with significant weight loss and abnormal imaging (e.g., tumors, strictures)
• Signs of intracranial pathology: vomiting alone with headache, neurologic symptoms, or altered mental status
• Unexplained metabolic acidosis with high anion gap (AG) → consider endocrine or ICU referral

🧪 What to Do Before Referral

• Urine hCG and urine ketones
• Basic labs: CBC, CRP, electrolytes, glucose, BUN/Cr, AST/ALT, blood gas if possible
• Bedside ultrasound (POCUS): hydration status, bowel loops, pregnancy-related findings
• Abdominal CT: only when obstruction, abscess, or mass is strongly suspected
• Organize key history: past illness, medications, menstrual and psychosocial background

📘 Column: Dealing with “Denial” in Eating Disorders

When referring for suspected eating disorders, patients often deny symptoms: “I eat normally” or “I haven’t lost weight.” Bring objective data—weight trend, menstrual history, and daily habits—to make your case stronger during referral.

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💡 Clinical Tips – Key Points for Nausea and Vomiting

• Don’t assume nausea always stems from the GI tract—consider the brain, heart, and metabolism too.
• The color, smell, and content of vomit are valuable clues—ask specifically.
• Vomiting without nausea is a potential Red Flag for increased intracranial pressure—consider head CT.
• In young women with dehydration and hypotension, always consider hyperemesis gravidarum—check hCG and urine ketones early.
• If the patient is on SGLT2 inhibitors, suspect EuDKA—even if the blood glucose is normal.
• Choose antiemetics based on the cause—avoid defaulting to metoclopramide alone.
• Use POCUS to visualize gastric content, bowel movement, and pelvic organs—it brings your history to life.
• Always ask yourself: “Does this patient look sick?”—vitals and facial expressions speak volumes.

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💬 Clinical Pearls – Quotable Lessons in English

• “All that vomits is not gastritis.”
  → Not every vomiting episode is due to gastritis. Think broader.
• “The absence of nausea does not mean the absence of danger.”
  → Vomiting without nausea can be a sign of raised ICP or brain pathology.
• “Trust the vomit’s story — it’s often more honest than the patient.”
  → Vomit characteristics (color, odor, contents) provide objective data that shouldn’t be ignored.
• “When in doubt, scan the head.”
  → A head CT can be lifesaving in unclear or neurologic cases.
• “Treat the patient, not just the puke.”
  → Don’t focus only on symptom relief. Always look for the underlying cause.

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🗣️ OET Speaking & Writing – Talking About Vomiting

👥 Scenario

You are a doctor in an urgent care clinic. A 23-year-old woman presents with nausea and repeated vomiting for the past 3 days. She is unable to eat or drink properly and feels dizzy when standing. You suspect hyperemesis gravidarum, but you also need to rule out other causes such as gastroenteritis, eating disorder, or metabolic imbalance.

🎯 Your Task

• Explain the possible diagnosis and what may have triggered it
• Discuss the importance of testing for pregnancy and dehydration
• Respond to patient concerns about serious conditions (e.g., infection or cancer)
• Reassure the patient and explain next steps in simple, clear language

💬 Common Patient Cues & Sample Doctor Responses

🧠 Challenging Questions & Sample Doctor Responses

✉️ OET Writing Task – Sample Referral Letter

Today’s Date

Dr. Maya Henderson
Obstetrics Department
St. Clara’s Women’s Hospital

Re: Ms. Julia Watanabe, 23 years old

Dear Dr. Henderson,

I am referring Ms. Julia Watanabe, a 23-year-old woman, for further management of suspected hyperemesis gravidarum. She presented with persistent nausea and vomiting for the past 3 days, unable to tolerate oral intake.

Her vital signs on arrival showed hypotension (BP 96/64 mmHg) and tachycardia (HR 110/min), with signs of clinical dehydration. She reported missing her last menstrual period by approximately one month and noted morning-predominant symptoms. Physical examination revealed mild abdominal distension without tenderness or guarding. Neurological exam was unremarkable.

Urine pregnancy test was positive, and urine ketones were moderate. Serum sodium was 130 mEq/L, and potassium 3.4 mEq/L. Blood gas showed mild metabolic acidosis with slightly elevated anion gap. Bedside ultrasound confirmed an intrauterine pregnancy with no abnormalities.

She has no significant medical history and is not currently on any medications. I would appreciate your evaluation for admission and continued care, including IV hydration and antiemetic therapy.

Please feel free to contact me if you need any additional information.

Yours sincerely,

Dr. [Your Name]
General Practitioner

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📝 Article Summary – Key Takeaways

Nausea and vomiting are common complaints, but they can signal much more than just a stomach bug. In this article, we approached them through a structured, clinical reasoning lens — following Steps 1 to 3:

• Step 1: History Taking – Go beyond asking “when did it start?” Dive into OPQRST and background history (PAM HITS FOSS) to detect hidden causes like pregnancy, eating disorders, or medication-related issues.
• Step 2: Physical Examination – Don’t just check the abdomen. Assess neurologic signs, hydration status, and consider Red Flags like vomiting without nausea or altered consciousness.
• Step 3: Investigations – Avoid blind testing. Instead, use hypothesis-driven strategies: check urine hCG, ketones, electrolytes, and blood gases. Use POCUS to visualize key findings quickly.

Final message: Vomiting is not just a symptom — it can be a message from the brain, the heart, or the body’s metabolic system. If you listen carefully and ask the right questions, you’ll not only avoid missing serious illness but also build trust with your patients.

In OSCEs or real-world clinics, this structured approach can help you move from simply “treating the symptom” to truly understanding the underlying cause.

Good luck — and trust your clinical instincts!

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🔗 Related Articles

• 🌀 Dizziness – When to Worry? A Stepwise Approach to Lightheadedness and Vertigo
• 🩺 Abdominal Distention – From Bloating to Palpable Masses: The “5F” Framework and Bedside Clues
• 💩 Constipation & Diarrhea – How to Approach Altered Bowel Habits
• 💓 Chest Pain – A Complete Diagnostic Guide Using History, Physical Exam, and POCUS
• 🇯🇵 【日本語版】嘔気・嘔吐の診かた

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📚 References

1. Tintinalli JE, et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9th ed. McGraw-Hill Education; 2020.
2. Jameson JL, et al. Harrison’s Principles of Internal Medicine, 21st ed. McGraw-Hill Education; 2022.
3. Kumar P, Clark M. Oxford Handbook of Clinical Medicine, 11th ed. Oxford University Press; 2023.
4. 日本救急医学会. 救急診療指針2024. 東京: 医学書院; 2024.
5. UpToDate. Approach to the adult with nausea and vomiting. Available at: www.uptodate.com [Accessed July 2025]

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