What are the differential diagnoses for a 27-year-old woman with a one-week history of nausea and vomiting and a negative pregnancy test?

Differential Diagnosis of One-Week Nausea and Vomiting in a 27-Year-Old Woman

In a 27-year-old woman with one week of nausea and vomiting and a negative pregnancy test, the differential diagnosis should prioritize acute infectious gastroenteritis, cannabinoid hyperemesis syndrome (if cannabis use present), medication adverse effects, acute migraine, vestibular disorders, and functional gastrointestinal disorders, while systematically excluding life-threatening conditions.

Immediate Life-Threatening Conditions to Exclude

Before considering benign causes, you must rule out emergencies that require hospitalization 1:

• Acute abdomen (appendicitis, cholecystitis, pancreatitis)
• Bowel obstruction
• Mesenteric ischemia
• Myocardial infarction (atypical presentation in young women)
• Intracranial pathology (if headache or neurologic signs present)

Primary Differential Diagnoses for One-Week Duration

Most Likely Acute Causes (Duration <7 Days)

Infectious/Inflammatory:

• Viral gastroenteritis - Most common cause of acute nausea/vomiting; typically self-limited 2
• Foodborne illness - Consider recent food exposures 2
• Other viral syndromes (respiratory infections, COVID-19)

Cannabinoid-Related (Critical to Assess):

• Cannabinoid hyperemesis syndrome (CHS) - Increasingly common in this age group (highest prevalence 16-34 years) 1. Key diagnostic clues:

  • Cannabis use >1 year, frequency >4 times/week 1
  • Compulsive hot water bathing/showering behavior (71% of cases) 1
  • Cyclic pattern with symptom-free intervals
  • Abdominal pain often present 1

• Cannabinoid withdrawal syndrome - If recently stopped heavy cannabis use (47% prevalence among users) 1

Medication/Toxin-Related:

• Medication adverse effects - Review all medications, supplements, and recent changes 2
• Toxin exposure

Neurologic:

• Acute migraine - Can present with prominent nausea/vomiting 2
• Vestibular disturbances (labyrinthitis, benign positional vertigo) 2

Transitioning to Chronic Causes (If Approaching 4 Weeks)

If symptoms persist beyond one week and approach 4 weeks, consider 3, 4:

Gastrointestinal:

• Gastroparesis - Requires gastric emptying study if suspected 3
• Peptic ulcer disease
• Gastric outlet obstruction
• Functional dyspepsia
• Cyclic vomiting syndrome (CVS) - Though typically requires recurrent episodes separated by symptom-free intervals 5

Endocrine/Metabolic:

• Thyroid disorders (hyperthyroidism, hypothyroidism)
• Adrenal insufficiency
• Diabetic ketoacidosis (if diabetic)
• Hypercalcemia
• Uremia

Psychiatric:

• Anxiety disorders
• Depression
• Eating disorders (bulimia nervosa)

Critical Historical Features to Elicit

Cannabis Use History:

• Duration, frequency, and route of use
• Hot water bathing behavior for symptom relief 1
• Recent cessation (withdrawal symptoms)

Symptom Characteristics:

• Timing: Continuous vs. episodic, time of day (early morning suggests CVS) 5
• Associated symptoms: Abdominal pain location/character, diarrhea, constipation, headache, fever, neurologic symptoms 5
• Triggers: Stress, foods, menstrual cycle, sleep deprivation 5
• Relieving factors: Position changes, hot showers, specific foods

Medication/Substance Review:

• All prescription medications, over-the-counter drugs, supplements
• Recent chemotherapy or radiation
• Alcohol use

Red Flag Symptoms (Alarm Features):

• Severe abdominal pain
• Significant headache with neurologic changes
• Hematemesis or melena
• Severe dehydration
• Weight loss
• Fever with rigors

Diagnostic Approach

Initial Laboratory Testing (if indicated by history/exam):

• Urinalysis and urine pregnancy test (repeat if high suspicion despite negative test)
• Complete blood count
• Comprehensive metabolic panel (electrolytes, glucose, renal function, liver enzymes)
• Amylase/lipase (if epigastric pain)
• Thyroid-stimulating hormone
• Stool studies with cultures (if diarrhea present)

Imaging (based on clinical suspicion):

• Abdominal radiography (if obstruction suspected)
• Abdominal ultrasound or CT (if acute abdomen suspected)
• Head CT (if intracranial process suspected)

Common Pitfalls

• Missing CHS diagnosis - Always ask about cannabis use and hot water bathing behavior in this age group; CHS prevalence is rising dramatically 1
• Assuming negative pregnancy test rules out pregnancy - Consider repeating if clinical suspicion high
• Overlooking medication causes - Review ALL substances including supplements and recreational drugs
• Premature diagnosis of functional disorder - Ensure adequate exclusion of organic causes first
• Ignoring psychiatric comorbidities - CVS and functional disorders often coexist with anxiety/depression 1