Functional dyspepsia and gastroparesis

• Functional dyspepsia is one of the commonest disorders of gut-brain interaction: long-standing epigastric pain or burning, or postprandial fullness and early satiety, with no structural disease to explain them.
• Gastroparesis is a far less common motility disorder: the same sort of upper-gut symptoms with objective, measured delay in gastric emptying and no mechanical obstruction.
• The two sit on a spectrum. Roughly a quarter to a third of people diagnosed with functional dyspepsia have some delay in gastric emptying, and a large minority of patients swap labels over time.
• Rome IV is the symptom-based framework for functional dyspepsia; gastroparesis is diagnosed by symptoms plus a delayed gastric emptying study, most reliably a 4-hour solid-meal scintigraphy.
• For functional dyspepsia, treatment is stepped and symptom-led: test and treat Helicobacter pylori, then a trial of a proton pump inhibitor, then a tricyclic antidepressant, then prokinetics. For gastroparesis, metoclopramide is the only drug approved in the United States, with several off-label prokinetics and antiemetics used when it fails.

By the end of this page you should be able to:

1. State the Rome IV criteria for functional dyspepsia, including the postprandial distress and epigastric pain subtypes.
2. Recognise the alarm (red-flag) features that should push you towards prompt endoscopy.
3. Explain how a gastric emptying study is done and what result counts as delayed emptying.
4. Describe the link between diabetes and gastroparesis, and how glucose control interacts with gastric emptying.
5. Compare the main prokinetic drugs used in gastroparesis, including doses and key cautions.
6. Outline the stepped management of functional dyspepsia and how it differs from gastroparesis.

Functional dyspepsia is the commoner of the two and is usually called a functional disorder: investigations are normal. Gastroparesis is rarer and is defined by an abnormal test. Both produce upper abdominal symptoms after eating.

Rome IV divides functional dyspepsia into two subtypes by symptom pattern ^[1].

• Postprandial distress syndrome (PDS): bothersome postprandial fullness and/or early satiety on at least 3 days per week. ^[1]
• Epigastric pain syndrome (EPS): bothersome epigastric pain and/or epigastric burning on at least 1 day per week. ^[1]

Both subtypes require symptoms for at least 3 months with onset at least 6 months before diagnosis. In practice the subtypes overlap in up to 35% of patients, and patients rarely fit neatly into one box.

The two conditions share almost identical symptoms, and the line between them is a measurement on a scan. Studies have found that between 25% and 37% of patients meeting criteria for functional dyspepsia have some delay in gastric emptying, and that many patients change labels over time even though their symptoms barely change ^[2]. A large retrospective cohort found that 42% of patients first diagnosed with gastroparesis were reclassified as functional dyspepsia after a later normal gastric emptying study, and 37% of patients first diagnosed with functional dyspepsia were later reclassified as gastroparesis ^[2]. Because of this overlap, many authorities now place the two at opposite ends of one spectrum of gastric sensorimotor dysfunction rather than treating them as entirely separate diseases ^[2].

That spectrum view matters clinically: it explains why prokinetics help both groups in trials, and why a patient's label should never be used to withhold a treatment that makes sense for their symptoms.

Functional dyspepsia is common. Depending on the criteria and population used, reported prevalence ranges from 7% to 45% of adults, with a Rome IV global prevalence estimated around 6.8% and rates of about 10% in Canada, the United States and the United Kingdom ^[1][3]. In Asia the rates are lower, roughly 6% in China versus 10% in the United States ^[3].

H. pylori is one plausible contributor to the geographic split. Asian populations have more H. pylori infection, and chronic H. pylori gastritis may alter gastroduodenal motility and reduce ghrelin secretion from gastric cells, which could delay gastric emptying and produce postprandial fullness. The postprandial distress subtype is more common in Asia, while the epigastric pain subtype is more common in Western cohorts ^[3].

Gastroparesis is much rarer. Using a United States national health-insurance database, the overall standardised prevalence was about 267.7 per 100,000 adults, falling to 21.5 per 100,000 when the stricter definition of delayed emptying with symptoms persisting for more than 3 months was applied ^[2][3]. Among patients in that database with available race data, 1.9% identified as Asian ^[3]. Women are affected more often than men, idiopathic gastroparesis in particular falls on young women, and using the United States clinformatics database diabetes was the single most common cause at 57.4% ^[3].

Gastroparesis is likely under-diagnosed outside the West. In some Asian countries more than 60% of institutions have no gastric emptying test at all, and survey work has reported that a quarter of Asian clinicians had never diagnosed gastroparesis in their career ^[3]. A survey-based estimate put gastroparesis-like symptoms at 0.3% in Singapore and 1.3% in South Korea among non-diabetic people, and 0.9% in South Korea and 4.5% in China among diabetic people ^[3].

No single cause has been identified. The current view is that functional dyspepsia is a multifactorial disorder of gut-brain interaction. Factors that have been associated with it include older age, female sex, low body mass index, H. pylori infection, use of aspirin or non-steroidal anti-inflammatory drugs, lower educational level, altered gastric accommodation, visceral hypersensitivity, duodenal eosinophilia and mast-cell activation, impaired duodenal barrier function, and psychological factors such as anxiety and depression ^[1].

Post-infectious functional dyspepsia following a bout of gastroenteritis is a recognised subset. H. pylori deserves special mention, because a subgroup of patients with dyspepsia (H. pylori-associated dyspepsia) improves after eradication. Most patients with true functional dyspepsia do not improve, so H. pylori is causative only in a minority ^[1].

Gastroparesis is classified by cause. The commonest etiologies are diabetes, idiopathic, drug-induced, post-surgical and viral ^[3]. Diabetes accounts for about 57.4% of cases in the United States database quoted above ^[3].

Drug-induced gastroparesis is important because it is potentially reversible. Medications that slow gastric emptying or function include opioids (including tramadol and tapentadol, which retard orocecal transit and gastric emptying respectively), anticholinergics, GLP-1 receptor agonists and cannabinoids. Narcotics must not be used to treat the pain of gastroparesis because they worsen emptying ^[4]. Post-surgical cases follow vagotomy, fundoplication, gastric bypass and other operations. Viral (including after norovirus) and connective tissue causes are less common.

Diabetes is the leading cause of gastroparesis worldwide, so any clinician who manages diabetes will meet it. In the United States database it produced 57.4% of gastroparesis cases, and the prevalence of diabetic gastroparesis is higher in type 2 than type 1 diabetes in at least one meta-analysis (12.5% versus 8.3%) ^[3][6].

The pathophysiology is autonomic neuropathy. Chronic hyperglycaemia damages the autonomic nerves of the stomach, most importantly the vagus, which is the longest autonomic nerve and carries roughly three-quarters of parasympathetic activity, so it is especially vulnerable in a length-dependent neuropathy. The result is reduced gastric accommodation, antral hypomotility, pyloric dysfunction and electrical dysrhythmia, together with altered visceral sensation. Gastroparesis is the commonest clinical manifestation of gastrointestinal autonomic neuropathy, which affects 30% to 50% of people with diabetes ^[6].

Acute hyperglycaemia itself delays gastric emptying in people with diabetes, and the DCCT/EDIC studies showed that delayed gastric emptying was associated with gastrointestinal symptoms and with both early and long-term hyperglycaemia ^[4]. Better glycaemic control is plausible good practice, but the evidence is nuanced: in one study 6 months of intensive therapy that lowered HbA1c from a mean of 10.6% to 9% did not change gastric emptying half-time, while a continuous insulin-infusion plus continuous glucose-monitoring study in 45 poorly controlled patients improved symptom scores and meal tolerance at 24 weeks ^[4]. One study also found that HbA1c level was significantly associated with the 4-hour retention value on nuclear gastric emptying scan ^[4]. The American College of Gastroenterology (ACG) guideline therefore suggests optimal glucose control in diabetic gastroparesis to reduce the risk of worsening, a conditional recommendation based on low-quality evidence ^[4].

Gastroparesis-related admissions have also risen, partly because of greater use of motility-impairing agents such as opioids, GLP-1 receptor agonists and recreational marijuana ^[6].

The exact mechanisms differ by condition.

In functional dyspepsia, current evidence supports a multifactorial disorder: impaired gastric accommodation, delayed gastric emptying in a subset, visceral hypersensitivity (especially in the epigastric pain subtype), central nervous system amplification of pain signals, duodenal eosinophilia and mast-cell activation, impaired duodenal barrier function, low-grade immune activation and altered gut microbiota. HPA-axis dysregulation and psychological distress feed back into motility and sensation. No single mechanism is dominant, and they interact through neural, hormonal and immune routes ^[1].

In gastroparesis, the core problem is delayed gastric emptying secondary to an abnormal enteric or extrinsic nerve drive: antral hypomotility, pyloric dysfunction (including reduced pyloric compliance), loss of interstitial cells of Cajal, electrical dysrhythmia (tachygastria or bradygastria), antroduodenal discoordination, impaired gastric accommodation and altered visceral sensation. In diabetes, vagal autonomic neuropathy is the central driver ^[3].

Both conditions share impaired gastric accommodation, visceral hypersensitivity and gut-brain dysregulation, which is the practical basis for the spectrum model.

Both diseases present with upper-gut symptoms. The patient commonly reports postprandial fullness, early satiety, epigastric pain or burning, nausea, bloating, belching and, in functional dyspepsia, sometimes weight loss from eating less ^[1][2].

The symptom balance differs on average. In functional dyspepsia the most common symptoms are postprandial fullness (86%), bloating (84%), epigastric pain (74%) and early satiety (72%) ^[2]. In gastroparesis nausea (96%) and vomiting (88%) are the most prevalent features, with postprandial fullness (68%) and bloating (52%) also frequent; early satiety and loss of appetite occur in 42% and 26% ^[2]. Nausea and vomiting are therefore the symptoms that should make you think of gastroparesis rather than functional dyspepsia, although the overlap is large.

Large subsets of both groups of patients also report nausea, vomiting and bloating, and symptom severity alone cannot separate the two. Objective gastric emptying testing is required where the distinction will change management.

Alarm features are the symptoms that raise the probability of organic disease (peptic ulcer, bleeding, malignancy) and should prompt prompt endoscopy rather than a symptom-based diagnosis of functional dyspepsia ^[1].

• Unintentional weight loss
• Gastrointestinal bleeding (haematemesis, melaena, iron-deficiency anaemia)
• Dysphagia
• Persistent vomiting
• Progressive dyspepsia in older adults
• Family history of upper gastrointestinal cancer
• Onset of symptoms at an older age, or symptoms in a region with high gastric cancer rates

Guidelines differ on the age at which uncomplicated dyspepsia without alarm features warrants endoscopy: 60 years in the North American guideline (with non-invasive H. pylori testing under 60) and 55 years in other reviews ^[1][3].

The main question is whether the patient has functional (no structural cause) or organic dyspepsia, and, if symptoms suggest gastroparesis, whether there is another cause of gastric stasis.

In a patient labelled with functional dyspepsia, persistent severe nausea and vomiting that does not respond to standard treatment should trigger a 4-hour solid-phase gastric emptying study, because gastroparesis explains poor response in many such patients ^[1].

A focused history and examination come first: symptom duration, character, relation to meals, medication list, alarm features and family history. Basic blood tests (full blood count, coeliac serology where indicated, metabolic profile) and non-invasive H. pylori testing (urea breath test or stool antigen) are the usual first steps in low-risk patients.

In patients with alarm features, or with age above the threshold, endoscopy excludes ulcers, erosions and malignancy. A normal endoscopy in a patient with epigastric symptoms is what allows a positive Rome IV diagnosis of functional dyspepsia, rather than a diagnosis of exclusion ^[1]. Retained gastric food seen on endoscopy has a positive predictive value for delayed gastric emptying of only 55% overall (32% in patients without risk factors, 79% in type 1 diabetes), and can be caused by medications such as opioids, acid suppressants and cardiovascular drugs, so it is not itself diagnostic of gastroparesis ^[4].

In low-risk dyspeptic patients without alarm features, guidelines recommend initial non-invasive testing for H. pylori and eradication if positive. This reduces the number of normal endoscopies. If H. pylori is negative, empirical acid suppression is the next step.

A 2022 meta-analysis of 29 randomised controlled trials in H. pylori-positive patients showed that eradication gave a statistically significant benefit for cure (relative risk for dyspepsia not cured 0.91; 95% CI 0.88 to 0.94) and for symptom improvement (relative risk for symptoms not improving 0.84; 95% CI 0.78 to 0.91) ^[1].

Gastric emptying scintigraphy is the standard test for gastroparesis and the only way to confirm the diagnosis objectively ^[3][4]. It should also be performed when functional dyspepsia is severe, atypical or unresponsive to standard therapy, and when persistent severe nausea and vomiting make gastroparesis likely ^[1].

How it is done ^[3][4][5]:

• The patient fasts and stops medications that affect gastric motility (opioids, cannabinoids, prokinetics, antiemetics and neuromodulators) for about 48 hours beforehand.
• A standardised solid meal is eaten, radiolabelled with technetium-99m, classically a low-fat egg-white meal (about 255 kcal, 2% fat) although higher-fat (300 kcal, 30% fat) egg-white meals are also used. ^[3]
• Imaging of the stomach is performed over at least 3 hours, and preferably 4 hours, to measure the percentage of the meal retained. Unless more than 90% of the meal has emptied by 3 hours, scanning to 4 hours is ideal. ^[4]
• A 13C-spirulina breath test is approved by the United States Food and Drug Administration and correlates well with scintigraphy; it is a good alternative when scintigraphy is unavailable.

What counts as delayed emptying depends on the meal and protocol ^[3][4][5]:

• With the standard low-fat egg meal (255 kcal, 2% fat), more than 10% retention at 4 hours defines delayed emptying. ^[4][5]
• With the higher-fat egg-white meal (300 kcal, 30% fat), more than 20% retention is abnormal.
• A common scintigraphic rule of thumb is gastric retention of more than 60% at 2 hours and/or more than 10% at 4 hours.
• An older radiopaque marker test is not recommended, because markers do not empty with solid food. A wireless motility capsule may be an alternative to scintigraphy but is less accurate for gastric emptying and gives more false-positive delayed results; it is now discontinued in many markets.

For the reasons above, a gastric emptying study done at one centre cannot always be compared directly with one done at another. Test meal composition, calories, fat content and duration of imaging all change the result, and the same patient can change classification on repeat testing.

Prokinetic, antiemetic and neuromodulating drugs should be stopped 48 hours before testing. Full-thickness gastric biopsies are reserved for research. Electrogastrography and other gastric function tests are research or adjunctive tools and do not replace scintigraphy. In diabetes, HbA1c is relevant because poor control worsens emptying. ^[4]

Rome IV requires one or more of the following, fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis, after exclusion of structural disease ^[1][2]:

• Bothersome postprandial fullness
• Bothersome early satiety
• Bothersome epigastric pain
• Bothersome epigastric burning

Subtypes are defined by frequency: PDS symptoms on at least 3 days per week, EPS symptoms on at least 1 day per week ^[1].

A working classification used in the literature, taken from the National Institute of Diabetes and Digestive and Kidney Diseases gastroparesis consortium and the United European Gastroenterology / European Society of Neurogastroenterology and Motility (UEG/ESNM) consensus, is ^[2]:

• Definite gastroparesis: delayed gastric emptying on standard scintigraphy plus symptoms (nausea and/or vomiting, postprandial fullness, early satiety, bloating or epigastric pain) for more than 3 months.
• Probable gastroparesis: the same symptoms plus retained food on endoscopy or an upper GI study, without scintigraphy.
• Possible gastroparesis: typical symptoms alone, or delayed emptying on scintigraphy without symptoms.
• Gastroparesis-like syndrome: typical symptoms with normal scintigraphy.

The gastroparesis cardinal symptom index is a patient-reported tool used in trials. It covers nausea, vomiting, postprandial fullness/early satiety and bloating. It allows tracking of severity over time but is not a diagnostic test ^[3].

Functional dyspepsia has no cure; the goal is symptom control and quality of life. The most-cited stepped algorithm comes from the 2017 joint ACG/Canadian Association of Gastroenterology (CAG) guideline, compared with the 2019 UEG/ESNM European guideline ^[1].

Step by step ^[1]:

1. H. pylori test and treat. First-line in positive patients, because eradication cures a minority and improves symptoms in more.
2. Proton pump inhibitor trial. An 8-week trial at standard daily dose. In a Cochrane review of 25 randomised trials, PPI and H2-receptor antagonist therapy did not differ significantly (relative risk 0.88; 95% CI 0.74 to 1.04), although the evidence is low quality. There is no benefit in doubling the proton pump inhibitor dose if 8 weeks fails. ^[1]
3. Antidepressant. Tricyclic antidepressants (such as amitriptyline) have shown a statistically meaningful benefit over placebo; selective serotonin reuptake inhibitors have not.
4. Prokinetics. Slight but statistically significant benefit across 26 randomised trials, but no prokinetic is currently marketed for functional dyspepsia in the United States, Canada or Europe. Metoclopramide has never been trialled in functional dyspepsia and its use here is guesswork. Domperidone data were judged biased and unclear.
5. Psychological therapy. Cognitive behavioural and other psychotherapies have shown benefit in trials similar to those in irritable bowel syndrome, but the evidence is limited, interventions can be expensive, and they require patient engagement.
6. Other factors. Reassurance, dietary advice, sleep hygiene, weight management and treatment of comorbid anxiety or depression are part of good care. Complementary and alternative therapy is not routinely recommended; individual agents such as the herbal preparation STW 5 or acupuncture have small trial support and uncertain benefit.

Targets differ by subtype. In Asian consensus, EPS is treated with a proton pump inhibitor with or without a prokinetic, and PDS with a prokinetic with or without a proton pump inhibitor ^[3]. Proton pump inhibitors are thought to help a subset with ulcer-like or reflux-like dyspepsia, and prokinetics help those with meal-related symptoms.

Long-term proton pump inhibitor use should be reassessed every 6 to 12 months, with withdrawal attempts as per United States Food and Drug Administration advice, because they are not risk-free. ^[1]

Gastroparesis management is harder, because the only drug approved by the United States Food and Drug Administration specifically for gastroparesis is metoclopramide. The guiding principles are ^[4][5]:

1. Exclude and treat reversible causes. Review all medications; stop opioids and anticholinergics where possible. Control glucose in diabetes.
2. Nutrition. Maintain oral intake if at all possible. A small-particle diet reduces symptoms and improves gastric emptying; avoid nondigestible fibre (anything that crunches) and very high-fat meals. Purée, soups and blenderised food are good proxies. If oral intake fails, progress to enteral feeding via jejunostomy, then (rarely) parenteral nutrition.
3. Pharmacotherapy. Metoclopramide first-line, then off-label prokinetics and antiemetics.
4. Procedures for refractory disease: gastric electrical stimulation, pyloromyotomy (G-POEM) and, rarely, surgery.

Only metoclopramide has direct FDA approval; everything else is off-label or experimental. Where availability is restricted (domperidone in the United States), local practice and formulary dictate choice.

Antiemetics such as 5-HT3 antagonists (ondansetron) and antihistamines (promethazine) control nausea and vomiting but do not accelerate gastric emptying ^[4].

Central neuromodulators (nortriptyline and similar drugs) are not recommended for gastroparesis; a well-designed nortriptyline trial was negative ^[4][5]. Haloperidol is not supported either. Herbal therapies such as rikkunshito and STW 5 (Iberogast) should not be recommended ^[4].

Gastric electrical stimulation may be considered for symptoms as a humanitarian-use device, and it appears most helpful for refractory vomiting. Intrapyloric botulinum toxin injection is not recommended on randomised trial evidence ^[4]. For refractory gastroparesis, pyloromyotomy (G-POEM) is suggested over no treatment for symptom control, largely on open-label data plus a pilot sham-controlled trial; gastric peroral endoscopic myotomy carries promising evidence, especially in refractory disease ^[4][5].

Because diabetes is the leading cause, diabetic gastroparesis deserves explicit attention ^[4][6].

• Glucose control. Acute hyperglycaemia delays gastric emptying and chronic hyperglycaemia is the principal driver of diabetic autonomic neuropathy. The ACG guideline suggests optimal glucose control to reduce the risk of worsening gastroparesis, although intensive control alone does not necessarily normalise gastric emptying half-time in trials. Continuous subcutaneous insulin infusion plus continuous glucose monitoring improved symptoms and meal tolerance in a small 24-week study ^[4]. HbA1c correlates with the 4-hour retention value on nuclear scan in one study ^[4].
• Glucose monitoring. Gastroparesis makes glucose erratic and hypoglycaemia risk unpredictable, so individualised insulin regimens and frequent glucose monitoring matter. Adjunctive agents that slow gastric emptying should be reviewed (for example GLP-1 receptor agonists).
• Diet. A small-particle diet is particularly well supported in diabetic gastroparesis, and a low-fat small-particle approach has demonstrated symptom relief plus improved gastric emptying and glycaemic control ^[4][5].
• Acupuncture may benefit diabetic gastroparesis specifically but cannot be recommended for other gastroparesis etiologies ^[4].
• Macrovascular and microvascular context. Gastroparesis is part of a wider diabetic autonomic neuropathy syndrome, so cardiovascular, renal and retinopathy screening are part of holistic care ^[6].

Functional dyspepsia rarely causes structural harm; its burden is quality of life, nutritional compromise and healthcare use. Occasional weight loss from eating less, anxiety and depression are common.

Gastroparesis carries a greater morbidity:

• Malnutrition and weight loss, dehydration, electrolyte disturbance
• Bezoar formation (retained food) and aggravation of symptoms
• Brittle or erratic diabetes control
• Aspiration risk in severe vomiting
• Increased hospitalisations
• Psychiatric morbidity from chronic illness
• Mortality in some series with severe disease and comorbidity

Gastroparesis also overlaps and is confused with functional dyspepsia, which leads to misdiagnosis and delayed care.

Functional dyspepsia is chronic and fluctuating but does not progress to malignancy or organ failure if the diagnosis is correct. Symptoms vary, and many patients respond to stepped therapy or reassurance.

Gastroparesis has a less favourable course, although many patients stabilise. Overlap with functional dyspepsia means that symptoms may improve even when emptying does not, and vice versa. Prognosis is worse in diabetic gastroparesis with poor control and in patients needing repeated hospitalisations. Long-term follow-up is sensible.

Pregnancy and breastfeeding. Data specific to functional dyspepsia in pregnancy are limited and a conservative approach is taken: non-pharmacologic measures and proton pump inhibitors with the best safety profile, with specialist input. Metoclopramide crosses the placenta; any prokinetic use in pregnancy is specialist-led. Domperidone is excreted in breast milk.

Children. Functional dyspepsia occurs in children and adolescents and is managed along adult principles; paediatric motility testing and drug licensing differ. Gastroparesis in children is most often post-viral or drug-induced.

Older adults. Comorbidity, polypharmacy and susceptibility to drug-induced extrapyramidal effects (metoclopramide) are heightened. New-onset dyspepsia in later life warrants more caution and a lower threshold for endoscopy.

Diabetes. See the diabetic gastroparesis section above. Type 2 diabetes is a more common setting than type 1 in most cohorts.

When gastric emptying scintigraphy is unavailable, clinicians rely on clinical judgement. The important points are:

• Many centres in Asia and other regions have no gastric emptying test at all, so patients with gastroparesis-like symptoms are often treated as functional dyspepsia ^[3].
• A careful endoscopy (where available) to exclude obstruction and gross pathology is the priority.
• Where nuclear medicine is absent, a clinical diagnosis of probable gastroparesis can be made on symptoms plus retained food on endoscopy, and treatment can proceed empirically.
• Proton pump inhibitors, domperidone (where licensed), erythromycin (cheaper macrolide) and dietary modification of texture and fat are low-cost, widely available options.
• In type 2 diabetes, optimising glucose control, even before specialist referral, is universally available and plausibly helps.
• Referral should be sought where possible for refractory cases, because severe disease benefits from specialised prokinetic and endoscopic intervention.

Related (plain text, not yet linked on this site): diabetes mellitus, Helicobacter pylori infection, gastro-oesophageal reflux disease, nausea and vomiting in adults, diabetes complications and autonomic neuropathy, irritable bowel syndrome, peptic ulcer disease.