Recommended diagnostic tests for confirming gastroparesis in patients with symptoms of delayed gastric emptying include gastric emptying scintigraphy as the gold standard investigation. This test quantitatively measures the rate of gastric emptying of a standardized meal and is widely endorsed in UK clinical practice guidelines for dyspepsia and related gastric motility disorders NICE CG184. Alternatively, breath tests using carbon-labeled substrates can be employed when scintigraphy is unavailable, providing a non-invasive assessment of gastric emptying. Additionally, upper gastrointestinal endoscopy is recommended initially to exclude mechanical obstruction or other structural causes of delayed gastric emptying before confirming gastroparesis NICE CG184. Emerging literature supports the use of wireless motility capsules and antroduodenal manometry for more detailed assessment of gastric motility patterns, although these are generally reserved for complex or refractory cases Hasler 2020.
In summary, the diagnostic pathway prioritizes exclusion of obstruction via endoscopy, followed by confirmation of delayed gastric emptying primarily through gastric emptying scintigraphy, with breath tests and advanced motility studies as adjuncts.