Causes of Intractable Nausea and Vomiting
Intractable nausea and vomiting results from identifiable structural, metabolic, medication-related, or functional causes that must be systematically evaluated and treated—the most critical reversible causes include gastric outlet obstruction, bowel obstruction, constipation, opioid use, hypercalcemia, and medication toxicity. 1
Structural/Mechanical Causes
The NCCN Palliative Care Guidelines emphasize that structural causes must be identified first as they often require urgent intervention 1:
- Gastric outlet obstruction - treat with corticosteroids initially; consider endoscopic stenting or decompressing G-tube if medical management fails
- Bowel obstruction (complete or partial)
- Severe constipation - particularly common with opioid use, occurring in ~50% of advanced cancer patients and most opioid-treated patients 1
Metabolic and Endocrine Causes
Check for hypercalcemia immediately in any patient with intractable vomiting, as this is a rapidly reversible cause 1. Additional metabolic causes include 2:
- Addison's disease (adrenal insufficiency)
- Hypothyroidism
- Hepatic porphyria
- Hyperammonemia
- Diabetic ketoacidosis
Medication-Induced Causes
Obtain blood levels of digoxin, phenytoin, carbamazepine, and tricyclic antidepressants as these commonly cause vomiting at toxic levels 1. Other medication causes:
- Opioids - consider opioid rotation if vomiting persists 1
- Chemotherapy agents (cisplatin, carboplatin, cyclophosphamide, doxorubicin)
- Anticholinergic medications
- Antacids
Gastrointestinal Causes
- Gastritis or gastroesophageal reflux - manage with proton pump inhibitors or H2 receptor antagonists 1
- Gastroparesis
- Functional dyspepsia
- Superior mesenteric artery syndrome 3
Neurologic Causes
Brain metastases and increased intracranial pressure are critical not-to-miss diagnoses 4. A particularly important but under-recognized cause is:
- Neuromyelitis optica spectrum disorder (NMOSD) - presents with intractable vomiting due to area postrema involvement; look for associated visual disturbances, nystagmus, or neurologic signs; confirm with aquaporin-4 (AQP4) IgG antibodies 5
- Posterior fossa tumors
- Hydrocephalus
Cannabis-Related Causes
In patients with chronic cannabis use, consider 6, 7:
- Cannabinoid hyperemesis syndrome (CHS) - requires prolonged (>1 year) and heavy cannabis use (>4 times weekly, often daily) preceding symptom onset
- Diagnosis requires 6 months or at least 3 typical cycle lengths of cannabis cessation to confirm
- Patients often report compulsive hot water bathing for symptom relief (44% in CVS patients) 7
Critical distinction: If cannabis use postdates vomiting onset or is only occasional, CHS is excluded and cyclic vomiting syndrome (CVS) is more likely 6
Functional Disorders
When structural and metabolic causes are excluded, consider 6:
- Cyclic vomiting syndrome - stereotypical episodes of acute-onset vomiting lasting <1 week, with at least 3 episodes in the previous year and 2 in the past 6 months, occurring at least 1 week apart; absence of vomiting between episodes
- Functional vomiting
- Chronic idiopathic nausea
Common Pitfalls
Do not perform repeated esophagogastroduodenoscopy or upper GI imaging once obstruction is excluded 6. If performed soon after a vomiting episode, recognize that mild gastritis, erythematous streaking, Mallory-Weiss tears, or esophagitis are epiphenomena of recent vomiting, not causal 6.
Avoid routine gastric emptying scans in CVS patients, as few have delayed emptying and results during an active episode are uninterpretable; cannabis or opiate use further complicates interpretation 6.
Do not stigmatize cannabis users - obtain a detailed timeline of cannabis use relative to symptom onset to distinguish CHS from CVS 6, 7.