How Should Unexplained Nausea and Vomiting Be Investigated?

Answer in brief: Persistent nausea and vomiting require a staged evaluation: first exclude urgent obstruction, metabolic disturbance, pregnancy and neurologic or medication causes; then use endoscopy or imaging when structural disease is plausible. Gastroparesis should be diagnosed only when symptoms coexist with objectively delayed gastric emptying and no mechanical obstruction; current AGA guidance favors a four-hour gastric emptying study over shorter protocols.[1]

Start with acuity and physiology

Acute severe vomiting with pain, distention, obstipation, GI bleeding, neurologic findings, major electrolyte disturbance or dehydration demands urgent assessment. Chronic nausea requires a broader history: meal relationship, early satiety, weight loss, cannabis use, migraine, vestibular symptoms, diabetes, prior surgery and medications.

Medication review has become central

GLP-1 receptor agonists, opioids, dopamine agonists, digoxin, antibiotics, chemotherapy and many other agents can delay gastric emptying or trigger nausea. Ask explicitly about cannabis and cannabinoid products because cannabinoid hyperemesis syndrome is frequently missed.

Exclude obstruction before diagnosing gastroparesis

Upper endoscopy and/or imaging are indicated when symptoms suggest gastric outlet obstruction, luminal disease or another structural cause. Retained food at endoscopy is a clue but is not by itself diagnostic of gastroparesis.

Test gastric emptying correctly

The 2025 AGA gastroparesis guideline suggests against two-hour or shorter studies compared with a four-hour gastric emptying study.[1] The result must be interpreted alongside symptoms and medication exposure. Prokinetics, opioids, GLP-1 drugs and glycemic status can meaningfully affect testing.

Broaden the differential when gastric emptying is normal

Functional dyspepsia or chronic nausea/vomiting syndromes.
Rumination syndrome.
Cyclic vomiting syndrome.
Cannabinoid hyperemesis syndrome.
Vestibular or central neurologic disease.
Migraine-related symptoms.
Pregnancy, adrenal, thyroid, renal or metabolic disorders.

Management follows the diagnosis

For confirmed gastroparesis, nutrition and glycemic optimization are foundational. AGA’s 2025 guideline conditionally supports metoclopramide and erythromycin, while discouraging several therapies as routine first-line choices.[1] For rumination or gut-brain disorders, behavioral therapy and diaphragmatic breathing may be more effective than escalating antiemetics.

Practical sequence

Stabilize dehydration/electrolytes and exclude emergencies.
Review medications, cannabis, pregnancy and systemic causes.
Use EGD/imaging if obstruction or mucosal disease is plausible.
If gastroparesis is suspected, obtain an appropriately performed four-hour gastric emptying study.
If emptying is normal, reconsider rumination, cyclic vomiting, functional dyspepsia and central causes.

Questions trainees should be able to answer

What must be excluded before diagnosing gastroparesis?
Why is a four-hour gastric emptying study preferred?
Which medication exposures commonly cause nausea or delay gastric emptying?

Frequently asked questions

Does retained food on EGD diagnose gastroparesis? No. It raises suspicion but objective gastric-emptying testing and exclusion of obstruction are required.

Should every patient with chronic nausea get a gastric emptying study? No. Testing is most useful when symptoms and clinical context suggest impaired gastric emptying.

What is new in gastroparesis guidance? AGA’s 2025 guideline emphasizes four-hour testing and individualized treatment; recommendations for many interventions remain conditional because evidence is limited.[1]

Free further reading from Dr. Thomson

GI Practice Review — free book library
First Principles of Gastroenterology and Hepatology — free book library

References

1. Staller K, Parkman HP, Leiman DA, et al. AGA Clinical Practice Guideline on the Management of Gastroparesis. Gastroenterology. 2025. doi:10.1053/j.gastro.2025.08.004.

2. Camilleri M, Kuo B, Nguyen L, et al. ACG Clinical Guideline: Gastroparesis. Am J Gastroenterol. 2022;117:1197-1220.

3. Thomson ABR. Practice Review in Gastroenterology. CAPstone Academic Publishers; 2014.

Educational use only. This article is intended for clinicians and trainees and does not replace patient-specific medical judgment or local guidance.