What is the workup for postprandial vomiting?

Diagnostic Workup for Postprandial Vomiting

The diagnostic workup for postprandial vomiting should begin with a thorough assessment for mechanical obstruction, gastroparesis, and functional disorders, as these represent the most common causes requiring specific interventions. 1

Initial Assessment

• Obtain detailed history focusing on timing of vomiting in relation to meals, character of vomitus (bilious, bloody, undigested food), associated symptoms, and duration of symptoms 1
• Evaluate for risk factors including diabetes, recent surgery, medication use (especially opioids, anticholinergics), and cannabis use 1
• Physical examination should focus on hydration status, abdominal tenderness, and presence of distension to identify potential complications 1
• Differentiate vomiting from regurgitation, rumination, and bulimia to ensure accurate diagnosis 1

Basic Laboratory Testing

• Complete blood count, serum electrolytes, glucose, liver function tests, and lipase to rule out metabolic causes and assess for complications (diagnostic yield 70-80%) 1
• Urinalysis to evaluate hydration status and rule out renal causes (sensitivity 90%, specificity 80%) 1
• For persistent vomiting >2-3 weeks, evaluate thiamin levels to prevent neurological complications 1

First-Line Diagnostic Tests

• Upper endoscopy (esophagogastroduodenoscopy) is essential to rule out mechanical obstruction before diagnosing a functional or motility disorder (diagnostic accuracy 95%) 1, 2
• Gastric emptying scintigraphy is the gold standard test for diagnosing gastroparesis (sensitivity 90%, specificity 80%) 1, 2
• The scintigraphy should be performed for at least 2 hours after ingestion of a radiolabeled meal, with 4-hour testing providing higher diagnostic yield and accuracy 1, 2

Proper Gastric Emptying Scintigraphy Technique

• The radioisotope must be cooked into the solid portion of the meal for accurate results 2
• A standardized low-fat, egg white meal labeled with 99mTc sulfur colloid consumed with jam and toast as a sandwich is recommended 2
• Medications that influence gastric emptying should be withdrawn for 48-72 hours prior to testing 2
• Blood glucose should be monitored and maintained within normal range during the test, as hyperglycemia itself can slow gastric emptying 2

Alternative Diagnostic Methods

• Breath testing using non-radioactive substances correlates well with scintigraphy and can be used as an alternative when scintigraphy is unavailable 2
• Antroduodenal manometry provides information about coordination of gastric and duodenal motor function and may help differentiate between neuropathic or myopathic motility disorders 2

Common Pitfalls to Avoid

• Relying solely on symptoms for diagnosis is inadequate as symptoms correlate poorly with the degree of gastric emptying delay 2
• Failure to control blood glucose during testing can lead to false positive results 2
• Not accounting for medications that can affect gastric emptying (prokinetics, opioids, anticholinergics) can lead to inaccurate results 2

Management Considerations

• Ensure adequate hydration with oral or intravenous fluids as needed to prevent dehydration and electrolyte imbalances 1
• Consider antiemetic therapy such as ondansetron for symptom control while completing diagnostic evaluation 1, 3
• For suspected gastroparesis, dietary modifications including smaller, more frequent meals with lower fat and fiber content may provide symptomatic relief 1, 4
• Evaluate and consider discontinuing medications that may cause or exacerbate vomiting 1