What is the differential diagnosis for a 15-year-old boy presenting with episodic abdominal colic and vomiting, with a normal ultrasound?

Differential Diagnosis for Episodic Abdominal Colic with Vomiting in a 15-Year-Old Boy with Normal Ultrasound

In a 15-year-old with episodic abdominal colic and vomiting with normal ultrasound, the most critical diagnoses to consider are cyclic vomiting syndrome (CVS) and cannabinoid hyperemesis syndrome (CHS), with CHS being particularly important given the age group and rising prevalence of cannabis use among adolescents. 1

Primary Differential Considerations

Cannabinoid Hyperemesis Syndrome (CHS)

• CHS should be suspected in any adolescent with chronic nausea and episodic vomiting, especially with cannabis use. 1
• Mean age of CHS patients is 30 years, but 69% are male, making this diagnosis highly relevant for a 15-year-old boy. 1
• Key diagnostic features include:
  • Stereotypical episodic vomiting resembling CVS with frequency ≥3 times annually 1
  • Cannabis use >1 year before symptom onset, with frequency >4 times per week on average 1
  • Compulsive hot-water bathing behavior (reported in 71% of cases) 1
• Resolution of symptoms requires cannabis cessation for at least 6 months or duration equal to 3 typical vomiting cycles. 1

Cyclic Vomiting Syndrome (CVS)

• CVS presents with stereotypical episodes of intense nausea and vomiting lasting hours to days, separated by symptom-free intervals. 1
• Four distinct phases characterize CVS: prodromal, emetic, recovery, and interepisodic phases. 1
• Cannabis use in CVS patients is typically occasional and often postdates the onset of episodic vomiting (making cannabis non-causal). 1
• Diagnostic workup should include one-time esophagogastroduodenoscopy to exclude obstructive lesions, blood work (CBC, electrolytes, glucose, liver function, lipase), and urinalysis. 1

Critical Distinguishing Features Between CHS and CVS

The key distinction is cannabis use pattern and temporal relationship: 1

• CHS: Prolonged (>1 year) and heavy cannabis use (>4 times weekly, often daily) precedes symptom onset 1
• CVS: Cannabis use is more occasional and often postdates the onset of episodic vomiting 1
• Hot-water bathing, while reported in both conditions, is more commonly considered an indicator of CHS 1

Other Important Differential Diagnoses

Intermittent Intestinal Obstruction

• While normal ultrasound reduces likelihood, intermittent malrotation with volvulus can present with episodic symptoms. 2, 3
• Consider if episodes include bilious vomiting, which indicates obstruction distal to the ampulla of Vater. 2, 4
• Upper GI series may be warranted if clinical suspicion remains high despite normal ultrasound. 2

Intermittent Intussusception

• Can present with crampy, intermittent abdominal pain manifested as episodes of severe discomfort. 2
• Progression to bilious vomiting suggests worsening obstruction. 2
• "Currant jelly" stools indicate mucosal damage and are concerning. 2

Metabolic/Endocrine Causes

• Addison's disease, hypothyroidism, and hepatic porphyria can mimic CVS and should be considered. 1
• Testing should be dictated by individual patient history. 1

Functional Disorders

• Functional chronic nausea and vomiting syndrome should be considered after exclusion of structural abnormalities. 1
• Gastroparesis is less common in CVS patients, and gastric emptying scans should not be ordered routinely. 1

Critical Pitfalls to Avoid

Do not dismiss episodic vomiting in adolescents without thoroughly assessing cannabis use patterns. 1

• Many patients with CHS remain uncertain about the role of cannabis and attribute symptoms to food, alcohol, stress, or existing GI disorders. 1
• Stigmatization of cannabis users can lead to underdiagnosis. 1

Avoid repeated esophagogastroduodenoscopy or upper GI imaging studies. 1

• If performed soon after a CVS episode, recognize epiphenomena of recent vomiting (mild gastritis, Mallory-Weiss tear, esophagitis) as not being causal. 1

Do not order gastric emptying scans routinely. 1

• Few CVS patients have delayed emptying, and results during an episode are uninterpretable. 1
• Cannabis or opiate use complicates interpretation. 1

Recommended Diagnostic Approach

1. Detailed cannabis use history: Duration, frequency, temporal relationship to symptom onset, and hot-water bathing behavior 1

2. Basic laboratory workup: CBC, electrolytes, glucose, liver function, lipase, urinalysis 1

3. One-time upper endoscopy to exclude obstructive lesions (if not previously done) 1

4. Selective testing based on clinical features:

   • Brain imaging if any localizing neurologic symptoms 1
   • Endocrine workup (Addison's, thyroid, porphyria) if clinically indicated 1
   • Upper GI series if concern for intermittent malrotation persists despite normal ultrasound 2

5. Therapeutic trial of cannabis cessation for 6 months or 3 typical cycle lengths if CHS suspected 1