Definitive diagnosis of<unk>  not typically made in ED
Gold standard is gastric emptying scintigraphy of a solid-phase meal
Other studies assessing emptying: tests, upper GI barium study, ultrasound for changes in antral area
ED workup to exclude alternative diagnoses and complications (e.g. dehydration, Electrolyte abnormalities)
CBC, BMP, LFTs, lipase
Urinalysis, uHCG
Consider:
ECG (if >50 or at risk for cardiac disease)
RUQ US
Acute abdominal series including an upright CXR (if risk for perforated ulcer)
CT abdomen/pelvis to rule out obstruction
Upper endoscopy or radiographic upper GI series to exclude mechanical obstruction or ulcer disease
Gold standard is gastric emptying scintigraphy of a solid-phase meal
Other studies assessing emptying: tests, upper GI barium study, ultrasound for changes in antral area
ECG (if >50 or at risk for cardiac disease)
RUQ US
Acute abdominal series including an upright CXR (if risk for perforated ulcer)
CT abdomen/pelvis to rule out obstruction
Upper endoscopy or radiographic upper GI series to exclude mechanical obstruction or ulcer disease
Gastroparesis
ACS/MI
Dysphagia
Boerhaave's
Dysuria
DKA
Constipation 
Intracranial Hemorrhage