TO THE EDITOR: Park et al1 examined functional dyspepsia (FD) using technetium-99m-phytate gastric emptying scintigraphy and reported no between-group difference in gastric emptying half-life, yet retention rates in the FD group were consistently lower than those in controls across time points.1 We commend the authors but note several protocol features that may have contributed to an appearance of relatively faster emptying and attenuate group differences.
First, the test meal was ~180 kcal. We acknowledge that Park et al1 described cultural and practical considerations for this meal choice; however, lower-calorie/low-fat meals are known to shorten gastric residence and may reduce detection of delayed emptying relative to the validated 255-kcal low-fat egg-white standard. Lower-calorie, low-fat meals shorten gastric residence and can reclassify delayed emptying as normal or rapid. Consensus statements recommend a standardized low-fat egg-white meal (~255 kcal) with fixed timing at 0, 1, 2, and 4 hours.2,3
Second, 4-hour imaging was conditional on the 2-hour result. Routine 4-hour acquisition detects more abnormalities than 2-hour protocols and is the basis of widely used reference values; therefore, we suggest obtaining 4-hour images in all subjects to align with widely used consensus protocols and reference values, not only those exceeding a 2-hour threshold.4-6
Third, baseline imbalances (higher rates of current smoking, higher body mass index, and diabetes in FD) may confound retention curves and group comparisons.1 Covariate-adjusted models (eg, mixed-effects analyses of retention over time with prespecified stratification by diabetes/body mass index) and sensitivity analyses using complete 0-4–hour data and 4-hour–only classification would clarify whether the “faster” pattern persists after addressing protocol-related bias.
In summary, the combination of a sub-255 kcal meal, non-mandatory 4-hour imaging, and metabolic confounding may partly account for the observed retention pattern in FD. We respectfully encourage the authors to provide the above sensitivity analyses to strengthen inference for clinicians and readers.
Footnotes
Financial support: This work was supported by the Soonchunhyang University Research Fund.
Conflicts of interest: None.
References
- 1.Park HL, Lee J, Kwon SJ, Lee S, Lee I, Oh JH. Clinical relevance of gastric emptying time in functional dyspepsia. J Neurogastroenterol Motil. 2025;31:366–373. doi: 10.5056/jnm24138. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Abell TL, Camilleri M, Donohoe K, et al. Consensus recommendations for gastric emptying scintigraphy: a joint report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine. Am J Gastroenterol. 2008;103:753–763. doi: 10.1111/j.1572-0241.2007.01636.x. [DOI] [PubMed] [Google Scholar]
- 3.Tougas G, Eaker EY, Abell TL, et al. Assessment of gastric emptying using a low fat meal: establishment of international control values. Am J Gastroenterol. 2000;95:1456–1462. doi: 10.1111/j.1572-0241.2000.02076.x. [DOI] [PubMed] [Google Scholar]
- 4.Ziessman HA, Bonta DV, Goetze S, Ravich WJ. Experience with a simplified, standardized 4-hour gastric-emptying protocol. J Nucl Med. 2007;48:568–572. doi: 10.2967/jnumed.106.036616. [DOI] [PubMed] [Google Scholar]
- 5.Guo JP, Maurer AH, Fisher RS, Parkman HP. Extending gastric emptying scintigraphy from two to four hours detects more patients with gastroparesis. Dig Dis Sci. 2001;46:24–29. doi: 10.1023/A:1005697422454. [DOI] [PubMed] [Google Scholar]
- 6.Pathikonda M, Sachdeva P, Malhotra N, Fisher RS, Maurer AH, Parkman HP. Gastric emptying scintigraphy: is four hours necessary? J Clin Gastroenterol. 2012;46:209–215. doi: 10.1097/MCG.0b013e31822f3ad2. [DOI] [PubMed] [Google Scholar]