Gastric Emptying Scintigraphy
The next best study is gastric emptying scintigraphy performed over 4 hours using a standardized radiolabeled solid meal. 1
Clinical Reasoning
This patient's presentation is classic for diabetic gastroparesis:
- Early satiety, postprandial bloating, epigastric pain, nausea, and vomiting are the cardinal symptoms of gastroparesis 2
- Uncontrolled type 2 diabetes is one of the three most common causes of gastroparesis (diabetic, idiopathic, and postsurgical) 2
- Unremarkable EGD appropriately rules out mechanical obstruction, which must be excluded before diagnosing a motility disorder 1
Proper Testing Protocol
Gastric emptying scintigraphy must be performed for at least 2 hours, with 4-hour testing providing higher diagnostic yield and accuracy. 1
Key technical requirements:
- Use a standardized low-fat egg white meal labeled with 99mTc sulfur colloid, consumed with jam and toast as a sandwich 1
- The radioisotope must be cooked into the solid portion of the meal for accurate results 1
- Shorter test durations (<2 hours) are inaccurate for determining gastroparesis 1
Critical Pre-Test Preparation
Before performing the study:
- Withdraw medications that influence gastric emptying for 48-72 hours (prokinetics, opioids, anticholinergics) 1
- Monitor and maintain blood glucose in the normal range during testing, as hyperglycemia itself can slow gastric emptying and cause false positive results 1
- Avoid smoking on the test day 1
Why Not Other Tests
Do NOT order gastric emptying studies routinely for bloating and distention alone, but gastric emptying scintigraphy is specifically indicated when nausea and vomiting are prominent symptoms, as in this patient. 3
Alternative methods exist but are less preferred:
- Breath testing using non-radioactive substances correlates well with scintigraphy and can be used as an alternative if scintigraphy is unavailable 1
- Antroduodenal manometry may help differentiate neuropathic versus myopathic motility disorders but is reserved for patients with persistent symptoms despite normal gastric emptying 1
Important Caveats
- Failure to demonstrate delayed gastric emptying does not necessarily rule out gastropathy 1
- Symptoms correlate poorly with the degree of gastric emptying delay, so relying solely on symptoms for diagnosis is inadequate 1
- In 30% of patients, the characterization of gastric emptying as normal, delayed, or rapid may differ between repeat studies, so a diagnosis based on a single study may occasionally be inaccurate 4
- A diagnosis of refractory gastroparesis requires persistent symptoms, particularly nausea and vomiting, in the context of reliably established gastric emptying delay 5