Internal Medicine
Gastroenterology
Vomiting And/or Nausea

Vomiting And/Or Nausea

Introduction

Nausea and vomiting are common presenting symptoms in various medical conditions. As a Canadian medical student preparing for the MCCQE1, understanding these symptoms' underlying mechanisms, causes, and management is crucial. This comprehensive guide will help you master the key concepts related to nausea and vomiting, with a focus on Canadian healthcare practices and guidelines.

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This article is tailored for MCCQE1 preparation, emphasizing Canadian medical practices and guidelines. It's essential to understand the unique aspects of managing nausea and vomiting in the Canadian healthcare context.

Pathophysiology

Understanding the pathophysiology of nausea and vomiting is crucial for MCCQE1 success. Let's break down the key components:

Step 1: Stimulation of the Vomiting Center

The vomiting center, located in the medulla oblongata, receives input from various sources.

Step 2: Activation of Efferent Pathways

Once stimulated, the vomiting center activates efferent pathways.

Step 3: Physiological Response

This leads to the physiological response of nausea and/or vomiting.

Key Anatomical Structures

  1. Chemoreceptor Trigger Zone (CTZ): Located in the area postrema of the medulla
  2. Vestibular System: Contributes to motion sickness
  3. Vagal and Splanchnic Nerves: Transmit signals from the gastrointestinal tract
  4. Cerebral Cortex: Involved in psychological causes of nausea and vomiting

Etiology

Understanding the diverse causes of nausea and vomiting is essential for MCCQE1 preparation. Here's a comprehensive list organized by systems:

  • Gastroenteritis
  • Peptic ulcer disease
  • Bowel obstruction
  • Appendicitis
  • Pancreatitis
  • Cholecystitis

Clinical Presentation

When assessing a patient with nausea and/or vomiting, consider the following:

  1. Onset and Duration: Acute vs. chronic
  2. Frequency and Timing: Relation to meals, time of day
  3. Associated Symptoms: Abdominal pain, fever, headache, etc.
  4. Vomitus Characteristics: Color, content (blood, bile)
  5. Aggravating/Alleviating Factors: Food, position changes
  6. Medications: Recent changes, new prescriptions
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In the Canadian healthcare system, it's important to consider the patient's cultural background and potential language barriers when taking a history. The MCCQE1 often includes questions on culturally sensitive care.

Diagnostic Approach

For MCCQE1 success, master this step-wise approach to diagnosing nausea and vomiting:

  1. Detailed History: Focus on onset, duration, and associated symptoms
  2. Physical Examination: Look for signs of dehydration, abdominal tenderness, neurological deficits
  3. Laboratory Tests:
    • Complete blood count (CBC)
    • Electrolytes, BUN, creatinine
    • Liver function tests
    • Pregnancy test in women of childbearing age
  4. Imaging Studies:
    • Abdominal X-ray: For suspected obstruction
    • CT scan: If intracranial pathology is suspected
  5. Specialized Tests:
    • Endoscopy: For suspected upper GI pathology
    • Vestibular function tests: For suspected vestibular disorders

Management

Understanding the management of nausea and vomiting is crucial for MCCQE1 success. Here's a comprehensive approach:

General Measures

  1. Fluid and Electrolyte Replacement: Crucial in preventing dehydration
  2. Dietary Modifications: Small, frequent meals; avoid trigger foods
  3. Antiemetic Medications: Choose based on underlying cause and patient factors

Pharmacological Management

Drug ClassExamplesIndications
Dopamine AntagonistsMetoclopramide, DomperidoneGastroparesis, chemotherapy-induced
Serotonin AntagonistsOndansetronChemotherapy-induced, postoperative
AntihistaminesDimenhydrinateMotion sickness, vertigo
AnticholinergicsScopolamineMotion sickness
Neurokinin-1 Receptor AntagonistsAprepitantChemotherapy-induced
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In Canada, domperidone is more commonly used than metoclopramide due to a lower risk of extrapyramidal side effects. This is an important distinction for the MCCQE1 exam.

Non-pharmacological Approaches

  1. Acupressure: P6 (Nei Kuan) point stimulation
  2. Ginger: Effective for pregnancy-related nausea
  3. Cognitive-behavioral therapy: For anticipatory nausea in chemotherapy patients

Canadian Guidelines

The Canadian Association of Gastroenterology provides guidelines for managing nausea and vomiting in specific conditions. Key points include:

  1. Pregnancy: First-line treatment is dietary and lifestyle modifications, followed by vitamin B6 and doxylamine if necessary
  2. Chemotherapy-induced: Use of 5-HT3 receptor antagonists as first-line therapy
  3. Gastroparesis: Domperidone is preferred over metoclopramide due to lower risk of neurological side effects

Key Points to Remember for MCCQE1

  • 🔑 Always consider pregnancy in women of childbearing age presenting with nausea and vomiting
  • 🔑 Domperidone is preferred over metoclopramide in Canada for gastroparesis
  • 🔑 Ondansetron is first-line for chemotherapy-induced nausea and vomiting
  • 🔑 Assess for red flags: hematemesis, severe abdominal pain, neurological symptoms
  • 🔑 Remember the CanMEDS roles, especially the Communicator role, when taking a patient history

Sample Question

A 28-year-old woman presents to her family physician with a 3-week history of nausea and vomiting, particularly in the morning. She reports feeling tired and having missed her last menstrual period. Which one of the following is the most appropriate next step in management?

  • A. Prescribe ondansetron
  • B. Order an abdominal ultrasound
  • C. Perform a urine pregnancy test
  • D. Start metoclopramide
  • E. Refer for upper endoscopy

Explanation

The correct answer is:

  • C. Perform a urine pregnancy test

This patient's presentation is highly suggestive of pregnancy. The combination of nausea and vomiting (particularly in the morning), fatigue, and missed menstrual period are classic symptoms of early pregnancy. In any woman of childbearing age presenting with nausea and vomiting, pregnancy should always be considered and ruled out before proceeding with further investigations or treatments.

A urine pregnancy test is a quick, non-invasive, and highly sensitive test that can confirm pregnancy. It's the most appropriate first step in this scenario. If positive, it would guide further management, including prenatal care and appropriate treatment for pregnancy-related nausea and vomiting (morning sickness).

The other options are less appropriate as initial steps:

  • A: Prescribing ondansetron without confirming the cause of nausea is premature and potentially harmful if the patient is pregnant.
  • B: An abdominal ultrasound might be considered later but is not the first-line test for suspected pregnancy.
  • D: Starting metoclopramide without a diagnosis is inappropriate and could be harmful in pregnancy.
  • E: Referral for upper endoscopy is invasive and unnecessary as a first step, especially given the high suspicion of pregnancy.

This question highlights the importance of considering pregnancy in women of childbearing age presenting with nausea and vomiting, a key point for the MCCQE1 exam.

References

  1. Canadian Association of Gastroenterology. (2019). Clinical Practice Guidelines for the Management of Nausea and Vomiting. Canadian Journal of Gastroenterology and Hepatology.

  2. Society of Obstetricians and Gynaecologists of Canada. (2021). Nausea and Vomiting of Pregnancy. Journal of Obstetrics and Gynaecology Canada.

  3. Longstreth, G. F., & Lacy, B. E. (2019). Approach to the adult with nausea and vomiting. In T. W. Post (Ed.), UpToDate. Waltham, MA: UpToDate Inc.

  4. Medical Council of Canada. (2023). Objectives for the Qualifying Examination - Gastroenterology. Retrieved from MCC Website (opens in a new tab)

  5. Royal College of Physicians and Surgeons of Canada. (2023). CanMEDS Framework. Retrieved from Royal College Website (opens in a new tab)