Gastroparesis
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Direct answer
Gastroparesis is delayed gastric emptying in the absence of mechanical obstruction, causing early satiety, nausea, bloating and vomiting of food eaten many hours earlier. Diabetes and idiopathic causes are the commonest, and the diagnosis is confirmed by gastric emptying scintigraphy showing more than about 10 per cent of a solid meal retained at four hours. Mechanical obstruction must be excluded first.
What you must remember
- Diabetic gastroparesis: The commonest identifiable cause; a diagnosis of exclusion, managed with tight glycaemic control.
- Idiopathic gastroparesis: A large group with no clear cause, some following a viral illness.
- Drug causes: Opioids, anticholinergics, tricyclic antidepressants and GLP-1 receptor agonists all slow gastric emptying.
- Post-surgical: Vagal injury after vagotomy or fundoplication can produce delayed emptying.
- Diagnosis: Upper GI endoscopy first to exclude obstruction, then gastric emptying scintigraphy with a solid meal, with retention above about 10 per cent at four hours.
- Prokinetics: Metoclopramide, with a tardive dyskinesia warning for prolonged use; erythromycin is a short-term option, and domperidone is used elsewhere with QT concerns.
A worked pathway: vomiting undigested food
A 46-year-old man with type 1 diabetes for 20 years has early satiety, vomiting of food eaten six hours earlier and a 6 kg weight loss. His HbA1c is high. The first step is a medication review, because opioids, anticholinergics and GLP-1 agonists can all slow emptying and change the cause. The second step is upper GI endoscopy to exclude pyloric stenosis, gastric outlet obstruction and malignancy, since these mimic gastroparesis. The third is gastric emptying scintigraphy with a standard solid meal, which in this case shows substantial retention at four hours.
With obstruction and drugs excluded, the diagnosis is diabetic gastroparesis. Management begins with glycaemic optimisation, because hyperglycaemia itself slows gastric emptying. The patient is advised to eat small, frequent, low-fat and low-fibre meals, and a short course of metoclopramide is considered, with the tardive dyskinesia risk explained. Electrolytes are checked because vomiting can cause hypokalaemia, and nutrition is assessed. Severe malnutrition may need nasojejunal feeding, and refractory cases are referred for endoscopic or surgical options.
Where the exam tries to catch you
The classic trap is attributing vomiting of undigested food to gastroparesis without endoscopy. Gastric outlet obstruction and gastric cancer produce the same symptoms, and endoscopy is the first test that excludes them. A second trap is the medication cause: GLP-1 receptor agonists delay gastric emptying, so the drug history must be checked before blaming diabetes. A third is metoclopramide. Its dopamine-blocking action carries a risk of tardive dyskinesia, especially with prolonged use, and examiners test this warning. Finally, the diagnosis rests on objective emptying tests, not symptoms alone, so a vignette that gives symptoms without a scintigraphy result is incomplete.
Frequently asked questions
What is the gold standard test for gastroparesis?
Gastric emptying scintigraphy with a standard solid meal is the reference test for gastroparesis, with retention above about 10 per cent at four hours indicating delayed emptying. Breath tests and capsule-based methods are alternatives in some centres.
Which prokinetic drug carries a risk of tardive dyskinesia?
Metoclopramide, a dopamine antagonist, carries a risk of tardive dyskinesia, especially with prolonged use, so it is given for limited periods in gastroparesis. Erythromycin, a motilin agonist, is an alternative for short-term use.
Which drugs can cause delayed gastric emptying and gastroparesis?
Opioids, anticholinergic drugs, tricyclic antidepressants and GLP-1 receptor agonists can all delay gastric emptying. A medication review is therefore a required part of the work-up before attributing gastroparesis to diabetes.
Why must mechanical obstruction be excluded in gastroparesis?
Mechanical obstruction, such as pyloric stenosis or gastric cancer, can mimic gastroparesis with vomiting and early satiety. Upper gastrointestinal endoscopy is therefore performed before accepting a diagnosis of gastroparesis.
What is the first step in managing diabetic gastroparesis?
Glycaemic control is the first step in managing diabetic gastroparesis, because hyperglycaemia slows gastric emptying. Dietary modification to small, frequent, low-fat and low-fibre meals is added before drug therapy.