Gastrointestinal · Case 05

Normal gastric emptying. No evidence of gastroparesis.

Imaging Findings

Anterior and posterior images initially show uptake within the stomach with progressive transition of activity into the small bowel. Gastric retention curves show less than 9% of activity within the stomach at 120 minutes.

Essential Facts

What is gastric empty study?

There are two types: the solid and liquid. 

The solid phase is more sensitive than the liquid for identifying delayed gastric emptying. To spare the patient radiation exposure, solid phase is the initially examination that is performed. Liquid emptying can be used over solid when a patient is allergic to eggs, cannot tolerate large volumes of solid food, or the solid phase was normal and the clinicians still have a high index of suspicion.

Lag phase: The delay before emptying begins

Standard method: geometric mean square root of the product of the anterior and posterior image counts at each time point

Scan Information

Indications:

    Gastroparesis: stomach does not empty normally
    Monitor effects in patient with abnormal gastric motility

With Solids:

  Emptying is linear after lag phase
  mix 0.5 to 1 mCi (18.5  to  37  MBq)  of  99mTc  sulfur  colloid  with scrambled egg whites served as white bread sandwich +30 g of strawberry jam and 120 mL water
  meal   must be consumed within 10 mins
  image upright immediately after meal then every 60 mins up to 4 hours
  children : stop at 2 hours
  patient should be sitting up between images
  must not consume any solids or liquids for the 4-hour period
  vomiting renders study invalid

Normal Findings:

Adult: Retention activity at 4 hours:0-10%

Clinical research studies (Arts 2005) have reported grading severity of gastric emptying though clinical correlation is recommended

Mild (Grade 1): 11-20% retention at 4 hours
Moderate (Grade 2): 21-35% retention at 4 hours
Severe (Grade 3): 36-50% retention at 4 hours.
Very Severe (Grade 4) : >50% retention at 4 hours

Delayed emptying may be due to:

Drugs (opiates, nifedipine)
Hyperglycemia without diabetic gastroenteropathy

With Liquids:

Liquid study in adults typically use radiolabeled water with normal T1/2 emptying time being less than 15 minutes

If we do a liquid study in pediatrics, we tag their formula/milk and it is generally accepted that a normal T1/2 for a milk study is <2 hours but this is under debate given the inability to perform a research study in the pediatric population to confirm normal emptying rates.

References

Mettler, Fred A., and Milton J. Guiberteau. Essentials of Nuclear Medicine Imaging. Elsevier/Saunders, 2012.