Evaluation of Cyclic Vomiting Syndrome
The appropriate evaluation for suspected cyclic vomiting syndrome requires a focused initial workup including basic blood work (CBC, electrolytes, glucose, liver function tests, lipase), urinalysis, and one-time upper endoscopy or upper GI imaging to exclude obstructive lesions, with additional testing only when specific clinical features suggest alternative diagnoses 1.
Initial Laboratory and Imaging Workup
The baseline evaluation should systematically exclude organic causes while avoiding unnecessary repeated testing:
Basic Laboratory Tests:
- Complete blood count
- Serum electrolytes and glucose
- Liver function tests
- Lipase
- Urinalysis 1
Structural Evaluation:
- One-time esophagogastroduodenoscopy (EGD) OR upper GI imaging to exclude obstructive lesions 1
- If EGD is performed soon after a CVS episode, recognize that mild gastritis, erythematous streaking, Mallory-Weiss tears, or esophagitis are epiphenomena of recent vomiting and not causal 1
- Avoid repeated EGD or upper GI imaging studies 1
What NOT to Order Routinely
Gastric emptying scans should NOT be ordered routinely because:
- Few CVS patients have delayed gastric emptying
- Results obtained during a CVS episode are uninterpretable
- Cannabis or opiate use further complicates interpretation 1
Conditional Testing Based on Clinical Features
Additional diagnostic testing should be dictated by individual patient history and specific clinical clues 1:
Consider testing for mimicking conditions when suggested by history:
- Addison's disease (adrenal insufficiency workup)
- Hypothyroidism (thyroid function tests)
- Hepatic porphyria (urine porphyrins)
- Metabolic disorders in children: aminoacidopathies, organic acidurias, fatty acid oxidation defects 2
Neurologic evaluation:
- Any localizing neurologic symptoms mandate brain imaging and neurology referral 1
- Consider in patients with concerning neurologic findings to exclude space-occupying lesions 2
Cannabis Use Assessment
A critical component of evaluation involves detailed cannabis use history 1:
Distinguish CVS from Cannabinoid Hyperemesis Syndrome (CHS):
- CHS criteria: Prolonged (>1 year) AND heavy cannabis use (>4 times weekly, often daily) that precedes symptom onset
- CVS pattern: Occasional cannabis use that often postdates the onset of episodic vomiting
- Diagnostic test: Cannabis cessation for 6 months or at least 3 typical cycle lengths; continued vomiting after this period rules out CHS 1
Screening for Comorbid Conditions
The evaluation should identify associated conditions that impact management 3:
- Migraine headaches (present in >40% of patients, with 38.9% family history) 4
- Anxiety and depression (present in ~30% of cases) 4
- Autonomic dysfunction
- Sleep disorders
- Substance use disorders
These comorbidities require referral to appropriate specialists (neurologist, psychiatrist, sleep specialist, psychologist, substance use specialist) 1, 3.
Common Pitfalls to Avoid
- Do not pursue repeated endoscopic or imaging studies once structural causes are excluded 1
- Do not use BMI as a screening tool for malnutrition - 47% of CVS patients may be overweight or obese despite 70% being at risk for malnutrition 5
- Do not dismiss patients who continue cannabis use - they should still be offered abortive and prophylactic therapy, which can be effective even with ongoing use 1
- Do not order gastric emptying studies routinely or during episodes 1
Nutritional Assessment
Given that malnutrition is common (70% at risk, 62.5% meeting criteria for malnutrition), consider validated nutritional screening tools like the Patient-Generated Subjective Global Assessment Short Form (PG-SGA-SF) or Malnutrition Screening Tool (MST), with referral to a registered dietitian nutritionist when indicated 5.