How is gastroparesis diagnosed on upper endoscopy in an adult with chronic nausea, vomiting of undigested food, early satiety, bloating, and risk factors such as diabetes, prior gastric surgery, neurologic disease, or opioid/anticholinergic use?

Gastroparesis Cannot Be Diagnosed on Endoscopy Alone

Endoscopy serves only to exclude mechanical obstruction—it cannot diagnose gastroparesis, which requires objective demonstration of delayed gastric emptying through gastric emptying scintigraphy or breath testing. 1

Role of Endoscopy in the Diagnostic Algorithm

Primary Purpose: Exclusion of Mechanical Obstruction

• Upper endoscopy (EGD) must be performed first to rule out mechanical gastric outlet obstruction, peptic ulcer disease, malignancy, or other structural lesions before diagnosing gastroparesis. 1, 2, 3
• The American Gastroenterological Association emphasizes that gastroparesis is defined as delayed gastric emptying in the absence of mechanical obstruction, making endoscopy a necessary exclusionary test rather than a diagnostic one. 1

Endoscopic Findings Are Non-Specific

• Endoscopy in gastroparesis patients may show retained food or bezoars in the stomach, but these findings are neither sensitive nor specific for gastroparesis. 4, 5
• A normal-appearing stomach on endoscopy does not rule out gastroparesis, and conversely, retained gastric contents do not confirm the diagnosis without objective gastric emptying testing. 1

Required Diagnostic Testing After Endoscopy

Gold Standard: Gastric Emptying Scintigraphy

• Gastric emptying scintigraphy performed for 4 hours after ingestion of a radiolabeled solid meal is the gold standard and required test to diagnose gastroparesis. 1, 2
• The test must use proper methodology: the radioisotope must be cooked into the solid portion of the meal (standardized low-fat egg white meal with 99mTc sulfur colloid). 1, 2
• Testing for less than 2 hours is inaccurate and should never be used—extending to 4 hours increases diagnostic yield by approximately 25% compared to 2-hour testing. 1, 2
• Normal gastric retention at 4 hours is <10%; gastroparesis is confirmed when retention is >10% at 4 hours. 2

Critical Testing Preparation

• Withdraw all medications that influence gastric emptying (prokinetics, opioids, anticholinergics, GLP-1 agonists) for 48-72 hours before testing. 2
• In diabetic patients, monitor and control blood glucose during testing—hyperglycemia itself slows gastric emptying and can cause false-positive results. 1, 2, 3
• Avoid smoking on the test day. 2

Alternative Diagnostic Methods

• Breath testing using non-radioactive 13C-octanoate correlates well with scintigraphy and serves as a validated alternative when scintigraphy is unavailable. 1, 2, 6
• Wireless motility capsule can assess gastric emptying time along with small bowel and colonic transit. 6
• Antroduodenal manometry should be reserved for patients with persistent symptoms despite normal gastric emptying, to differentiate neuropathic versus myopathic motility disorders. 1, 2

Clinical Diagnostic Algorithm

Step 1: Clinical Assessment

• Evaluate for cardinal symptoms: nausea, vomiting (especially of undigested food), early satiety, postprandial fullness, bloating, and epigastric pain. 1, 7
• Identify risk factors: diabetes (especially long-standing type 1), prior gastric surgery, neurologic disease, medications (opioids, anticholinergics, GLP-1 agonists), or recent viral illness. 1, 3, 5

Step 2: Upper Endoscopy

• Perform EGD to exclude mechanical obstruction, peptic ulcer disease, malignancy, and other structural abnormalities. 1, 2, 3

Step 3: Objective Gastric Emptying Testing

• If endoscopy shows no mechanical obstruction, proceed with 4-hour gastric emptying scintigraphy using proper methodology. 1, 2
• If scintigraphy is unavailable, use 13C-octanoate breath testing as an alternative. 1, 2

Step 4: Additional Testing if Needed

• If gastric emptying is normal but symptoms persist, consider antroduodenal manometry to evaluate for other motility disorders. 1, 2
• Consider wireless motility capsule or EndoFLIP for assessment of pyloric dysfunction in patients being considered for pyloric-directed therapies. 6

Common Pitfalls to Avoid

• Never diagnose gastroparesis based on symptoms alone or endoscopic findings of retained food—objective delayed gastric emptying must be documented. 1
• Do not rely on 2-hour or shorter gastric emptying studies, as they miss approximately 25% of gastroparesis cases. 2
• Failure to discontinue gastroparesis-exacerbating medications before testing leads to false-positive results. 2
• In diabetic patients, uncontrolled hyperglycemia during testing causes false-positive results. 1, 2
• Symptoms correlate poorly with the degree of gastric emptying delay—do not assume severe symptoms indicate severe gastroparesis or vice versa. 1, 7

Therapeutic Implications of Proper Diagnosis

• Proper diagnosis with documented delayed gastric emptying is essential before initiating prokinetic therapy, considering gastric electrical stimulation, or pursuing advanced interventions like G-POEM. 1
• For patients being considered for advanced therapies (gastric electrical stimulation or G-POEM), gastric retention >20% at 4 hours is preferred, as this threshold predicts better clinical success. 2