Comparison of Ultrasound and Scintigraphy in Gastric Emptying: A Comprehensive Review.

Gastric emptying is the process by which gastric contents are transferred from the stomach to the small intestine for further digestion and nutrient absorption. It is the result of multiple gastrointestinal mechanisms and is essential for understanding the kinetics of digestion in humans. Delayed gastric emptying is clinically relevant as it is commonly observed in conditions such as gastroparesis and functional dyspepsia. A wide range of diagnostic modalities are available to assess gastric emptying, including scintigraphy, ultrasonography, magnetic resonance imaging, gastric aspiration, and stable isotope breath tests. Scintigraphy is widely regarded as the 'gold standard' technique, as it enables a direct quantitative assessment of gastric emptying following ingestion of a radiolabeled meal(s). Scintigraphy is non-invasive, reproducible, widely available, and well tolerated; however, it lacks standardized protocols, is time-consuming, costly, and necessitates exposure to ionizing radiation. Although the radiation dose is low, cumulative exposure remains a concern, particularly in pediatric and pregnant populations. In contrast, ultrasonography is safe, non-invasive, portable, inexpensive, and free from radiation exposure. Nevertheless, the application of ultrasound is limited by operator dependency and the need for technical expertise, and image quality may be affected by factors such as obesity and intraluminal gas. Furthermore, there is substantial methodological variability across studies, and its use in assessing gastric emptying of semisolid and solid meals is less well established. 3D ultrasonography, in particular, shows promise as a safe, non-invasive method for assessing gastric emptying. Further studies are required to promote the consistent application of established scintigraphic gastric emptying protocols across centers and to validate 3D ultrasound, particularly with solid meals, to potentially enhance its role as an alternative to scintigraphy. This article represents a comprehensive review based on a structured literature search with the primary aim of comparing ultrasonographic and scintigraphic measurements of gastric emptying, including the advantages and disadvantages of both methods.