What are the differential diagnoses for nausea and vomiting?

Differential Diagnosis for Nausea and Vomiting

The differential diagnosis for nausea and vomiting is extensive and must systematically evaluate gastrointestinal, medication-related, metabolic, neurologic, and psychiatric causes, with particular attention to life-threatening conditions and commonly missed diagnoses.

Medication and Toxin-Related Causes

• Opioid therapy causes nausea in up to 50% of patients, particularly with initiation or dose escalation 1
• Cardiac and neurologic medications including digoxin, phenytoin, carbamazepine, and tricyclic antidepressants require therapeutic drug monitoring when suspected 1
• Chemotherapy and radiation therapy are major contributors with substantial impact on quality of life 2, 3, 1
• Cannabis use is associated with cannabinoid hyperemesis syndrome (CHS), cyclic vomiting syndrome (CVS), and cannabinoid withdrawal syndrome 4

Gastrointestinal Causes

• Constipation, especially in opioid-treated patients, is frequently overlooked but common 1
• Gastric outlet obstruction and bowel obstruction (mechanical or functional) must be excluded 2, 1
• Gastritis and gastroesophageal reflux disease respond to proton-pump inhibitors or H₂-receptor antagonists 1
• Gastroparesis requires gastric emptying study for diagnosis 5, 6
• Gastroenteritis and viral syndromes are typical causes of acute symptoms 7, 6
• Foodborne illness presents with acute onset 7

Metabolic and Endocrine Causes

• Hypercalcemia is a critical trigger, particularly in oncologic patients, and is frequently missed 1
• Pregnancy must be considered in all women of childbearing age; nausea and vomiting of pregnancy typically begins at 4-6 weeks gestation and peaks at 8-12 weeks 8, 1, 9
• Hyperemesis gravidarum is defined by severe nausea/vomiting beginning before 16 weeks gestation with inability to eat/drink normally and strongly limiting daily activities 8
• Electrolyte disturbances including hyponatremia, hypokalaemia, and metabolic alkalosis 8, 1
• Organ system failure including uremia 2, 1
• Thyroid dysfunction occurs in two-thirds of women with hyperemesis gravidarum 8
• Diabetes can cause gastroparesis 2

Neurologic Causes

• Central nervous system pathology including increased intracranial pressure, brain metastases, tumors, or structural lesions 2, 1, 6, 9
• Cyclic vomiting syndrome presents with stereotypical episodes of acute-onset vomiting lasting less than 1 week, with at least 3 discrete episodes in the previous year and absence of symptoms between episodes 4, 10
• CVS triggers include stress, sleep deprivation, hormonal fluctuations, infections, and migraine history 4, 10, 1
• Vestibular dysfunction and motion sickness 7, 6
• Acute migraine headaches 7, 6

Psychiatric and Functional Causes

• Anxiety and panic disorders may present with nausea; benzodiazepines can be useful for anxiety-related symptoms 1
• Anticipatory nausea and vomiting occurs as a conditioned response after negative past chemotherapy experiences, with incidence ranging from 18% to 57% 2
• Psychogenic disorders should be considered in chronic cases 11, 6, 9

Critical Pitfalls to Avoid

• Do not attribute nausea to opioids without first evaluating for constipation, which is common and readily treatable 1
• In cancer patients, hypercalcemia is frequently missed and must be actively screened 1
• Mechanical bowel obstruction should not be overlooked, particularly in patients with abdominal malignancies or prior abdominal surgery 1
• Hot-water bathing is not pathognomonic for cannabinoid hyperemesis syndrome; approximately 48% of CVS patients without cannabis exposure exhibit this behavior 4, 1
• Ketonuria is not an indicator of dehydration in pregnancy and should not be used to assess severity of hyperemesis gravidarum 8

Temporal Classification

• Acute nausea and vomiting lasts up to 7 days and is typically self-limited, often from gastroenteritis, viral syndromes, or medication effects 7, 6
• Chronic nausea and vomiting persists for 4 weeks or longer and requires systematic evaluation for underlying pathology 7, 5, 11
• Delayed-onset symptoms develop more than 24 hours after chemotherapy administration, reaching maximal intensity at 48-72 hours with cisplatin 2