What are the causes of nausea in a patient, excluding pregnancy?

Causes of Nausea Aside from Pregnancy

Nausea in non-pregnant patients stems from gastrointestinal obstruction, medications (especially opioids and chemotherapy), metabolic derangements (hypercalcemia, hypokalemia, hyperglycemia), gastroparesis, constipation, brain metastases, and infectious gastroenteritis—with the specific cause determined by timing, associated symptoms, and medication history. 1, 2

Gastrointestinal Causes

Mechanical Obstruction and Motility Disorders

• Gastroparesis presents with postprandial fullness, early satiety, and delayed gastric emptying, affecting 20-40% of diabetic patients and 25-40% of those with functional dyspepsia 2
• Gastric outlet obstruction and bowel obstruction are common in advanced colorectal and ovarian cancer, causing persistent nausea 1
• Constipation is present in 50% of advanced patients and is frequently overlooked but readily treatable, particularly with opioid use 2
• Gastroesophageal reflux and gastritis cause nausea that responds to proton pump inhibitors or H2-receptor antagonists 1

Infectious and Inflammatory

• Viral gastroenteritis appears in epidemics with sudden onset, mild fever, diarrhea, and relatively short duration 1
• Systemic infections including sepsis, pneumonia, otitis media, and meningitis can manifest with nausea 1

Medication and Toxin-Related Causes

High-Risk Medications

• Opioids cause nausea through direct stimulation of the chemoreceptor trigger zone and delayed gastric emptying 1, 2
• Chemotherapy agents (particularly cisplatin) would cause nausea in nearly 100% of patients without prophylactic antiemetics 1
• Anticholinergic medications impair gastrointestinal motility and contribute to nausea 1
• Antipsychotics with opioid agonist properties (like lurasidone) stimulate the chemoreceptor trigger zone 3
• Check blood levels of digoxin, phenytoin, carbamazepine, and tricyclic antidepressants as potential culprits 1

Metabolic and Endocrine Causes

Critical Metabolic Derangements

• Hypercalcemia directly causes gastric dysmotility and is common in malignancy 1, 2
• Hypokalemia and hypomagnesemia impair gastrointestinal function 2
• Hyperglycemia in diabetic patients causes antral hypomotility and delayed gastric emptying 2
• Hypothyroidism slows gastrointestinal transit 2
• Metabolic disorders including phenylketonuria, hyperammonemia, maple syrup urine disease, galactosemia, and adrenocortical hyperplasia cause nausea in infants 1

Neurologic Causes

Central Nervous System Pathology

• Brain metastases and increased intracranial pressure from tumors, trauma, or hydrocephalus present with nausea, enlarging head circumference (in infants), bulging fontanelle, and neurologic signs 1
• Vestibular disturbances including motion sickness cause nausea through inner ear dysfunction 4
• Acute migraine headaches commonly present with nausea as a primary symptom 4

Cancer-Related Causes (Non-Chemotherapy)

Direct Disease Effects

• Malignant bowel obstruction occurs particularly in advanced colorectal and ovarian cancer 1
• Disease involving the gastrointestinal tract or abdomen causes nausea in 4-44% of cancer patients depending on site and stage 1
• Gastric ulcer disease and gastric volvulus are less common causes 1

Psychiatric and Functional Causes

Anxiety and Functional Disorders

• Anxiety-related nausea responds to benzodiazepines 1, 2
• Irritable bowel syndrome commonly occurs and may present with nausea 5
• Cyclic vomiting syndrome represents a distinct disorder with episodic severe nausea and vomiting 6

Diagnostic Approach by Timing

Acute Nausea (Up to 7 Days)

• Typical causes include gastroenteritis, viral syndromes, foodborne illness, acute migraine, vestibular disturbances, and medication adverse effects 4
• In the absence of alarm symptoms, treat symptomatically without extensive evaluation 4

Chronic Nausea (4 Weeks or Longer)

• Requires systematic evaluation to distinguish gastrointestinal from non-gastrointestinal causes 6
• After excluding anatomic, mechanical, and biochemical causes, categorize based on gastric emptying (delayed versus normal) 6

Critical Alarm Features Requiring Urgent Evaluation

• Bilious emesis suggests obstruction distal to the ampulla of Vater 1
• Repeated forceful vomiting warrants evaluation for underlying obstruction 1
• Weight loss exceeding 5% indicates severe pathology 1
• Neurologic signs including altered consciousness, focal deficits, or seizures 1
• Signs of dehydration or electrolyte abnormalities 1

Common Pitfalls to Avoid

• Do not overlook constipation as a readily treatable cause, especially in patients on opioids or with advanced disease 2
• Do not assume gastroparesis without confirming delayed gastric emptying via 4-hour gastric emptying scintigraphy 2
• Do not miss metabolic causes by failing to check calcium, potassium, magnesium, glucose, and thyroid function 2
• Do not ignore medication review as the most common reversible cause of nausea 2
• Do not use antimotility agents (like loperamide) when gastroparesis or obstruction is suspected, as they worsen symptoms 2