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Nuclear medicine · Gastroenterology

Gastric emptying scan, 4-hour scintigraphic test for gastroparesis and rapid gastric emptying.

A 4-hour scintigraphic gastric emptying scan measures the percentage of a Tc-99m-labelled standard meal remaining in the stomach at 1, 2, 3 and 4 hours. The gold-standard test for gastroparesis (delayed emptying) and dumping syndrome (rapid emptying).

A patient at a London clinic undergoing a gastric emptying scan under a gamma camera

Key facts

What a gastric emptying scan is, in six lines.

The essentials - what the test measures, what the meal is, what the threshold means, and who reads it.

  • 4-hour scintigraphic gastric emptying study

  • Standard low-fat egg-white meal with Tc-99m label

  • Emptying at 4 hours < 90% = gastroparesis

  • Very rapid emptying suggests dumping syndrome

  • Reported by a nuclear medicine consultant

  • Complements gastroscopy and manometry

Preparation and pathway

From referral to plan - what happens, in order.

The seven steps of a standard 4-hour scintigraphic gastric emptying study.

  1. 01

    Before

    Gastroenterology referral

    A gastroenterology referral confirms the scan is the right next step, with prokinetics and diabetic control noted.

  2. 02

    Before

    Fast for 6 hours

    Nothing to eat for 6 hours before the appointment. Sips of water are fine.

  3. 03

    Before

    Withhold prokinetics for 48 hours

    Metoclopramide, domperidone, prucalopride and erythromycin are held for 48 hours unless your gastroenterologist advises otherwise.

  4. 04

    On the day

    Consume the Tc-99m egg-white meal

    A standardised low-fat egg-white meal is labelled with Tc-99m and eaten within 10 minutes under supervision.

  5. 05

    On the day

    Serial gamma-camera images

    Images are acquired immediately after the meal and at 1, 2, 3 and 4 hours - you sit or lie under the gamma camera for a few minutes each time.

  6. 06

    After

    Nuclear medicine reporting

    A consultant nuclear medicine physician calculates the percentage retention at each time point and issues a written report.

  7. 07

    After

    Structured plan with your gastro

    Your gastroenterologist reviews the report and sets the treatment plan - dietary, prokinetic, endoscopic or surgical.

Typical appointment: ~4 hours. Report: within a few working days.

What it shows

When a gastric emptying scan is the right test.

The scan answers a specific question - how fast the stomach empties, and whether that fits with symptoms. These are the most common presentations.

  • Delayed gastric emptying (gastroparesis)

    The gold-standard diagnostic finding - retention above published thresholds at 2 and 4 hours.

  • Very rapid emptying (dumping)

    Excessive early emptying suggests dumping syndrome, often after gastric surgery.

  • Reflux during scanning

    The gamma camera can pick up reflux of the labelled meal into the oesophagus.

  • Post-surgical anatomy alteration

    Changes after fundoplication, sleeve gastrectomy or bypass are visible on the study.

  • Response to prokinetic therapy

    Repeat studies quantify how much a prokinetic drug has changed emptying.

  • Baseline before bariatric surgery

    Baseline emptying informs surgical planning and post-op comparison.

  • Post-fundoplication assessment

    Assesses emptying after anti-reflux surgery when symptoms persist.

  • Red flag: severe gastroparesis with malnutrition - nutritional support and MDT

    Severe delay with weight loss and dehydration needs urgent nutritional support and MDT input.

Treatment options / next steps

What happens after an abnormal scan.

A stepped ladder - dietary first, then prokinetics, then endoscopic and surgical options for refractory cases.

  • Dietary modification

    Small, low-fat, low-fibre meals eaten frequently - the first-line intervention for most patients.

  • Prokinetics

    Metoclopramide, domperidone or prucalopride to accelerate emptying, with cardiac and neurological monitoring.

  • Erythromycin as prokinetic

    Motilin agonist used short-term for symptomatic control when other prokinetics fail.

  • Gastric pacing (specialist)

    Implanted gastric electrical stimulator for refractory diabetic or idiopathic gastroparesis.

  • Endoscopic pyloromyotomy (G-POEM)

    Endoscopic division of the pylorus - an increasingly used option for outlet-obstruction gastroparesis.

  • Pyloric botulinum injection

    Temporary chemical relaxation of the pylorus, sometimes used to predict G-POEM response.

  • Bariatric surgery consideration

    In selected patients with severe gastroparesis, gastrectomy or bypass may be considered by an MDT.

  • MDT gastroenterology follow-up

    Long-term follow-up in a specialist motility clinic with dietitian and endocrine input where relevant.

Safety and eligibility

Safe, low-dose, well-tolerated.

A low-dose nuclear medicine study - the practical points are fasting, held medications and pregnancy.

  • Very low radiation dose

    The Tc-99m dose is small and comparable to a few months of natural background radiation.

  • Pregnancy - relative contraindication

    Not offered in pregnancy unless the clinical need is exceptional and consultant-approved.

  • Breastfeeding

    Short interruption of breastfeeding is usually advised - the team gives specific timings.

  • Fast for 6 hours

    Nothing to eat for 6 hours beforehand. Sips of water are fine.

  • Withhold prokinetics 48 hours

    Metoclopramide, domperidone, prucalopride and erythromycin are stopped for 48 hours before the scan.

  • Diabetic patients

    Blood glucose above 15 mmol/L can slow emptying artefactually - the team may reschedule if levels are high.

  • Egg allergy

    Tell the team in advance - an alternative meal preparation is used.

  • Opiates and cannabinoids

    Both delay emptying and should be paused, where safe, in the days before the scan.

  • Bring your medication list

    A full list of current medications and doses helps interpretation and the onward plan.

Red flags and higher-risk groups

When the scan and the plan matter most.

Groups in which findings materially change management, and where an MDT view is often needed.

  • Severe gastroparesis with dehydration

  • Malnutrition secondary to gastroparesis

  • Post-vagotomy gastroparesis

  • Diabetic gastroparesis

  • Neurodegenerative disease (Parkinson’s)

  • Amyloidosis

  • Post-radiotherapy gastroparesis

  • Dumping syndrome with hypoglycaemia

  • Pregnancy (relative contraindication)

Reading your report

A gastric emptying report can look intimidating. It isn’t.

Whatever the finding, the report keeps to the same four parts.

A London consultant nuclear medicine physician reviewing gastric emptying scintigraphy images

A quiet reminder

The report is written for your doctor, not for you - and that’s normal.

Ask your clinician to talk you through it before your follow-up.

  1. 01 Header

    Indication and medications

    Your details, the reason for the scan and the medications that could influence emptying.

  2. 02 Technique

    Meal, isotope dose and imaging schedule

    The labelled meal used, the Tc-99m dose administered and the times images were acquired.

  3. 03 Findings

    Percentage retention at 1, 2, 3 and 4 hours

    The gastric retention percentages at each time point, compared against published normal ranges.

  4. 04 Impression

    The conclusion: read this first

    Normal, delayed (gastroparesis) or rapid (dumping) emptying, with the concrete next step.

Recognised by major UK insurers

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Frequently asked

Common questions about gastric emptying scans.

Quick answers on the meal, the radiation, held medications, and what an abnormal scan means for treatment.

  • What does a gastric emptying scan show?

    The percentage of a standardised low-fat Tc-99m-labelled egg-white meal remaining in the stomach at 1, 2, 3 and 4 hours. Retention above published thresholds means gastroparesis; very rapid emptying suggests dumping syndrome.

  • How long does the test take?

    The whole appointment runs for about 4 hours. You eat the labelled meal and then return under the gamma camera for a few minutes at 1, 2, 3 and 4 hours.

  • Is it safe? What about the radiation?

    The Tc-99m dose is small and roughly comparable to a few months of natural background radiation. It is not offered in pregnancy unless the clinical need is exceptional.

  • Do I have to fast?

    Yes - nothing to eat for 6 hours before the scan. Sips of water are fine.

  • Which medications do I need to stop?

    Prokinetics (metoclopramide, domperidone, prucalopride, erythromycin) are held for 48 hours unless your gastroenterologist tells you otherwise. Opiates and cannabinoids should also be paused where safe.

  • What happens if my scan is abnormal?

    A gastroenterologist reviews the report and sets a plan - dietary changes and prokinetics first, then G-POEM, gastric pacing or bariatric surgery in refractory cases.

Sources

Published 2026-07-30 · Written by the Pulse Atlas editorial team · Next review 2027-07-30 · 5 min read

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In practice, in London

The London pathway for gastric emptying scan

With gastric emptying scan, the London question is usually about report turnaround and the radiologist reading it - not whether the scan is available. On the NHS, gastric emptying scan typically sits behind a triage step and a wait that can stretch from a few weeks into months. In London’s private sector, the same appointment often lands within days. That speed matters when symptoms are disrupting work, sleep, or a plan you’d already committed to - and it’s the single most common reason people consider going private in the first place.

The mechanics are straightforward: a consultant appointment, any tests done at a nearby CQC-registered site, and a written report back within a few days. London’s density of private diagnostics - Marylebone, the City, Chelsea, Canary Wharf - means most patients can find something that fits around work without a cross-town trek. For gastric emptying scan specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.

Honesty about expectations is part of the job. A private gastric emptying scan appointment in London won’t change the underlying medicine - the guidelines, the consultants, and the equipment are largely the same as on the NHS. What it changes is speed, continuity, and the amount of time you get to actually talk through the findings. Consultants working in the UK are GMC-registered, and private facilities in England are regulated by the CQC.