What is the appropriate diagnostic and management approach for a patient presenting with persistent vomiting for 3 months, considering potential underlying gastrointestinal conditions?

Differential Diagnosis for Persistent Vomiting (3 Months)

For an adult with persistent vomiting lasting 3 months, the differential diagnosis must systematically address gastrointestinal, neurologic, metabolic, psychiatric, and medication-related causes, with the diagnostic approach prioritizing exclusion of mechanical obstruction, gastroparesis, and cyclic vomiting syndrome. 1

Critical Initial Categorization

Determine if the vomiting pattern is continuous versus episodic, as this fundamentally changes the differential diagnosis:

• Continuous daily vomiting suggests gastroparesis, mechanical obstruction, medication effects, metabolic disorders, or functional disorders 1, 2
• Episodic vomiting with well periods strongly suggests cyclic vomiting syndrome (CVS), which requires ≥3 discrete episodes in a year with 2 occurring in the prior 6 months, each lasting <7 days and separated by at least 1 week of baseline health 3

Primary Differential Diagnoses

Gastrointestinal Causes

Mechanical obstruction must be ruled out urgently, particularly if bilious vomiting is present, as this represents a surgical emergency requiring immediate fluoroscopy upper GI series 4:

• Malrotation with volvulus (can present at any age, not just neonates) 5
• Adhesions from prior surgery
• Malignancy causing gastric outlet obstruction
• Hiatal hernia 5

Gastroparesis is a leading cause of chronic vomiting and requires gastric emptying scintigraphy (2-4 hour study) for diagnosis 4:

• Diabetic gastroparesis
• Post-viral gastroparesis
• Idiopathic gastroparesis

Peptic ulcer disease and malignancy require upper endoscopy if symptoms persist beyond 7 days or worsen despite treatment 4

Cyclic Vomiting Syndrome

CVS should be strongly suspected if stereotypical episodes of acute-onset vomiting occur, lasting <7 days, with at least 3 discrete episodes in a year 3:

• Prodromal symptoms include impending sense of doom, panic, fatigue, mental fog, restlessness, anxiety, headache, bowel urgency, diaphoresis (70-80% of patients), or flushing 3
• Personal or family history of migraine is present in 20-30% of CVS patients 3
• Critical pitfall: Screen for cannabis use >4 times weekly for >1 year, as this suggests cannabinoid hyperemesis syndrome (CHS) rather than CVS, requiring 6 months of cessation to differentiate 3, 4
• Hot water bathing is NOT pathognomonic for CHS and occurs in 48% of CVS patients who don't use cannabis 4

Neurologic Causes

Increased intracranial pressure from tumor, trauma, or hydrocephalus typically causes other neurologic signs 5:

• Headache pattern changes
• Visual disturbances
• Focal neurologic deficits
• Altered mental status

Metabolic and Endocrine Causes

Pregnancy must be considered in any woman of childbearing age 1, 6

Metabolic disorders include 5:

• Diabetic ketoacidosis
• Adrenal insufficiency
• Hypercalcemia
• Uremia
• Thyroid disorders

Medication and Toxin-Related Causes

Opioids cause nausea in 10-50% of patients 4

Other common culprits include:

• Chemotherapy agents 1
• Antibiotics 4
• Recent anesthesia 4

Psychiatric Causes

Psychiatric comorbidities are present in 50-60% of CVS patients and should be screened in all patients with chronic vomiting 3:

• Anxiety disorders
• Depression
• Panic disorder
• Bulimia nervosa
• Rumination syndrome

Diagnostic Approach Algorithm

Step 1: Immediate Red Flags (Require Urgent Evaluation)

• Bilious vomiting = surgical emergency until proven otherwise 4
• Acute abdomen (severe abdominal pain, distention, absent bowel sounds) = immediate surgical consultation 4
• Severe dehydration or metabolic abnormalities 7
• Altered sensorium or neurologic signs 7

Step 2: Pattern Recognition

• Episodic with well periods: Pursue CVS diagnosis with cannabis screening 3, 4
• Continuous daily: Pursue gastroparesis, obstruction, medication causes 4, 1

Step 3: Initial Testing

Basic laboratory evaluation 6, 8:

• Complete metabolic panel (electrolytes, glucose, renal function, liver function)
• Complete blood count
• Thyroid-stimulating hormone
• Pregnancy test (if applicable)
• Urinalysis

Imaging 6, 8:

• Plain abdominal radiography to assess for obstruction
• Upper GI series if bilious vomiting or obstruction suspected 4

Step 4: Advanced Testing Based on Clinical Suspicion

• Upper endoscopy if symptoms persist >7 days to exclude mechanical obstruction, peptic ulcer disease, malignancy 4
• Gastric emptying scintigraphy if gastroparesis suspected (requires 2-4 hour study) 4
• Head CT if intracranial process suspected 8

Common Pitfalls to Avoid

• Missing medication causes: Always review opioids, chemotherapy, antibiotics, and recent anesthesia 4
• Misinterpreting hot water bathing: This occurs in 48% of CVS patients without cannabis use and is not specific to CHS 4
• Overlooking psychiatric comorbidities: Present in 50-60% of CVS patients and treating underlying anxiety can decrease episode frequency 3
• Assuming all episodic vomiting is CVS: Must screen for cannabis use >4 times weekly for >1 year to differentiate CHS 3, 4
• Delaying endoscopy: Patients with alarm symptoms or risk factors for gastric malignancies require esophagogastroduodenoscopy 8