Gastroparesis is one phenotype with three failure points: the vagus for accommodation and coordination, the interstitial cells of Cajal for rhythm, and smooth muscle for force. Diabetes hits two of the three, surgery hits the vagus, idiopathic disease hits the pacemaker, and drugs mimic the whole picture by slowing the antrum. Four-hour scintigraphy with strict drug holds and controlled glucose anchors the diagnosis, and the favored move is often to stop a drug rather than confirm a disease. Topics covered Three-system model of gastric emptying Diabetic and idiopathic gastroparesis GLP-1 agonists and drug-induced delay Four-hour gastric emptying scintigraphy Pre-test drug holds and glucose control Prokinetic drugs by mechanism Antiemetics and refractory interventions Emptying-symptom mismatch Key decisions Diagnose delayed emptying only with four-hour scintigraphy: more than 10 percent retained at four hours is diagnostic; grade severity as mild 10-15, moderate 15-35, severe over 35 percent. Confirm glucose under 200 before testing, hold prokinetics 2-3 days (false negatives), hold opioids, anticholinergics, cannabinoids, and tobacco (false positives); for delayed emptying on a GLP-1 agonist, stop the drug and repeat only if symptoms persist. Scope first to exclude obstruction, bezoar, or pyloric stenosis before ordering the emptying study, especially in a diabetic with vomiting. Metoclopramide is the only approved prokinetic, first-line, capped near 12 weeks for tardive dyskinesia risk; prolactin elevation makes it the favored cause of secondary amenorrhea in a young woman. Domperidone needs a baseline ECG and QTc below 450 in men, 470 in women; IV erythromycin is the most effective agent for an acute inpatient flare but oral form fails long-term via tachyphylaxis. Intrapyloric botulinum toxin is recommended against and is the favored wrong answer; gastric electrical stimulation helps diabetics with severe vomiting, and G-POEM suits selected refractory patients with real baseline retention. For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected]. (00:00) - Three failure points (01:24) - Diabetic gastroparesis (02:14) - Idiopathic and post-surgical causes (03:02) - Drug causes and GLP-1 agonists (05:03) - Diagnostic workup and scintigraphy (08:35) - Treatment foundation and diet (09:55) - Prokinetic drugs by mechanism (14:49) - Refractory options and next episode

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