Gastric emptying: methodology and normal ranges for two commonly used meals in the UK
Authors: Hansrod Shazmeen , James Gregory , Notghi Alp , Croasdale Jilly , O’Brien Joseph , Thomson William H. 
Published: May 2020

Aim
A recent audit has highlighted that there is a large variation in the way gastric emptying scintigraphy is performed, analysed and reported in the UK. In this study, we have established a comprehensive protocol on how to perform gastric emptying including normal ranges for two of the most widely used meals. A standardized scrambled egg sandwich was used as the main meal. Normal ranges were also established for oat porridge as an alternative gluten-free meal. We have calculated normal ranges for several functional parameters which may be used to assess gastric emptying. We hope that establishing a reliable normal range for these two simple and commonly used meals will encourage adoption of a universally accepted protocol for measurement of solid gastric emptying in the UK.

Method
A total of 42 volunteers (20 male, 22 female, age range 22–68) with no history of gastrointestinal symptoms or diabetes were studied. Each volunteer fasted overnight and consumed two meals with similar nutritional composition on two separate days: scrambled eggs with two slices of bread were consumed on one day and gluten-free porridge (40 g in 200 mL whole milk) was consumed on a different day. Each meal was radiolabelled with 10 MBq of 99mTc-DTPA. Simultaneous anterior–posterior 2-min static images were acquired with the patient standing between the gamma camera detectors. Images were acquired every 5 min over a 2 hour period, followed by a single image at 3 hour. The data were modelled using a power-exponential function that allowed measurements of gastric emptying functional parameters including lag time, half-emptying time (HET), peak emptying rate, time-to-peak emptying (TPE) and exponential half-life (EHL). Three-hour retention was also calculated. Paired t-tests were used to compare the two meals and two-sample t-tests were used to assess gender-related differences. Regression analysis was used to assess correlation of the functional parameters with age and body habitus (body surface area, BSA).

Results
All gastric emptying functional parameters were significantly different between the two meals (P < 0.001). The normal range for lag time was 0–13 min for porridge and 1–34 min for scrambled egg. The normal range for HET was 18–73 min for porridge and 44–116 min for scrambled egg. The normal range for EHL was 21–57 min for porridge and 20–82 min for scrambled egg. The normal range for 3 hour retention was <7% for porridge and <17% for scrambled egg. Only weak significance was found for gender-related differences in gastric function for the two meals (0.05 < P < 0.10). Weak correlation was also observed for some functional parameters when plotted against age and BSA (0.05 < P < 0.10).

Conclusion
We have established gastric emptying normal ranges for the two most commonly used meals in the UK. The normal ranges are meal specific and not interchangeable, with porridge showing significantly faster transit than scrambled egg for all measured parameters. Scrambled egg sandwich is the recommended meal for solid gastric emptying studies as it is more reproducible and more comparable to a normally consumed solid meal for our population. Porridge would be a suitable alternative for patients who are unable to eat egg sandwiches, for example, patients with egg allergy or gluten intolerance.