Optimization and Standardization of Gastric Emptying: Getting the Most Out of this Valuable Diagnostic Tool

1138 Background: Gastrointestinal diseases are a pervasive medical problem, representing almost 20% of primary care visits and approximately $30 billion in healthcare costs each year. The breadth and heterogeneity of clinical presentations create significant challenges for both primary care physicians and subspecialists alike. Introduced in 1966, gastric emptying scintigraphy (GES) is performed via radiolabeling of the solid or liquid component of a meal which is then consumed and the gastric counts measured by scintigraphy (1). For a long time, there was a lack of standardization in GES, including differences in meal, patient preparation, image acquisition, and variations in the quantitative data reported (2). The lack of standardization limited the clinical utility of GES, making it difficult to interpret or compare results from other institutions and often leading to repeat testing. In order to eliminate this significant shortcoming, consensus guidelines were formulated by the Society of Nuclear Medicine and the American Neurogastroenterology and Motility Society in 2007 (3-5). The guidelines provided a simple and easy to follow protocol for patient preparation, exam performance and reporting. Despite being adopted by both the ACR and SNMMI, a decade later Farrell et al. found that only 3% of nuclear medicine practices were compliant with the 2007 protocol (2). Purpose and Educational Goals The purpose of this exhibit is to review the current role of GES in the diagnostic toolset for evaluating gastric motility, the research supporting its utilization, as well as the appropriate methodology and interpretation of GES studies. Cases will be used to highlight the spectrum of normal and abnormal findings for both solid and liquid meals. In this exhibit, we will describe the pathophysiology and classification of abnormal gastrointestinal motility. We will review the consensus guidelines for performing standardized solid and liquid GES (3). We will discuss the interpretative criteria for GES. Lastly, we will discuss the future of GES, including intragastric differential distribution. Key teaching points The symptoms of gastrointestinal transit disorders are extremely common in primary care patients and lead expensive medical care. Symptoms include dysphagia, nausea, vomiting, early satiety, bloating, pain, diarrhea, and constipation. The Rome diagnostic criteria were created to help diagnose and treat gastrointestinal disorders, with the latest iteration being the Rome IV diagnostic criteria. Current diagnostic tools for evaluating gastrointestinal transit disorders include the use of endoscopy, manometry, barium fluoroscopy, motility capsules and gastric emptying breath tests. The strong benefits of GES are its ability to quantitatively and qualitatively analyze gastrointestinal motility disorders. The 2007 GES consensus guidelines are based on the protocol by Tougas et al (6). The GES protocol consists of a standard low-fat meal that needs to be completed within a limited time, with defined imaging time points. Gastrointestinal functional disorders are defined by counts at the defined time points. GES in the diagnosis of functional disorders is an evolving field. The regional distribution of radioactive counts within the stomach has been shown to help diagnose different functional disorders. Conclusions: GES is a very useful diagnostic modality in the evaluation of gastrointestinal disease, providing a qualitative and quantitative assessment of gastric motility under physiologic conditions. GES is a well-established tool in the diagnosis of gastroparesis as well as useful in characterizing rapid emptying and regional gastric functional disorders. Because of the persistent variation in the practice of GES, despite long-standing national guidelines, it is important that radiologists and nuclear medicine physicians be knowledgeable of its proper performance and interpretation.