Functional Dyspepsia 101: Causes, Symptoms, and Treatment.

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1. What do we mean by “functional” and “Dyspepsia”?

Dyspepsia is defined as difficulty digesting food. It is also called indigestion.

Dyspepsia often causes trouble in the upper abdomen, such as discomfort, fullness, pain, or burning in the upper stomach area.

Functional is a term used to describe disorders without evident disease or lesion.

Functional dyspepsia (FD) is also called:

  • Non-ulcer dyspepsia (dyspepsia without having stomach ulcers or gastritis).
  • Idiopathic dyspepsia (because the exact cause of functional dyspepsia is still unclear).

How common are dyspepsia and functional dyspepsias?

Dyspepsia is a very, very common complaint. One study estimated that about 38% of people experience indigestion (dyspepsia).

Not all dyspepsia is functional. Dyspepsia can be due to organic diseases such as chronic gastritis and peptic ulcer disease.

However, Functional dyspepsia is still the most common cause of dyspepsia. One study estimated that 75% of dyspepsia causes are functional dyspepsia (FD), and only 25% are due to organic reasons.


2. Causes of Functional dyspepsia.

We still don’t know the exact causes and mechanism of dyspepsia. Functional dyspepsia is also called (idiopathic) as we don’t fully understand its origin.

All we have are theories with little or inconsistent evidence in research.

And here are the most common theories about functional dyspepsia.

1. Abnormal Motility of the stomach:

Motility diseases are associated with dyspepsias such as gastroparesis (slow motility of the stomach), Rapid gastric emptying, impaired gastric accommodation to meals, and antral hypermotility (reference).

However, Motility abnormalities are found in only 25-35% of functional dyspepsia patients (reference).

2. Visceral Hypersensitivity.

Feeling pain at lower thresholds of stomach distension. Average amounts of food inside your stomach or duodenum are perceived as stomach distension which causes dyspepsia symptoms.

In one study, 37% of patients with functional dyspepsia had hypersensitivity to gastric distension (reference).

3. H. Pylori infection.

H. pylori is a bacteria infection of the stomach. It commonly causes gastritis and peptic ulcer disease. In addition, recent research found that it can be involved in Functional dyspepsia.

The mechanisms by which H. pylori cause functional dyspepsia are unclear. More research is needed.

4. Altered gut microbiome.

Your stomach and intestine contain billions of non-harmful micro-organisms. They’re collectively called the (gut microbiome).

Alternating the balance between the good and harmful bacteria inside your stomach and small intestine can give rise to functional dyspepsia.

Alternation of the gut microbiome can be due to medications such as antibiotics or severe infections.

Also, this theory of (altered microbiome) cannot fully explain functional dyspepsia.

5. Psychological dysfunction (anxiety, depression, and others).

Dyspepsia is more common among people with anxiety disorders, depression, somatization, and among victims of child abuse (emotional and physical) (reference).

6. Duodenal inflammation.

The presence of inflammatory cells such as eosinophils and mast cells inside the duodenum of functional dyspepsia patients is common (reference). However, These types of cells can also present in healthy individuals.

3. Symptoms of functional dyspepsia.

No single test or imaging technique can diagnose functional dyspepsia. We diagnose functional dyspepsia on symptom-based criteria.

However, you can not diagnose yourself with functional dyspepsia. And here is why:

  • Diagnosing (functional) dyspepsia necessitates the exclusion of other causes of dyspepsia (such as peptic ulcers, h. pylori infection, etc.).
  • Your doctor has to perform an endoscopy and some tests to ensure no other (organic) causes of dyspepsia.

The most famous criteria for diagnosis of functional dyspepsia are the ROME IV criteria (reference):

Functional Dyspepsia ROME IV Criteria.

1. One or more of the following:
a. Bothersome postprandial fullness
b. Bothersome early satiation
c. Bothersome epigastric pain
d. Bothersome epigastric burning
2. AND
No evidence of structural disease (including at upper endoscopy) that is likely to explain the symptoms
* The above criteria must be fulfilled for the last three months
* symptom onset at least six months before diagnosis.

The two types of functional dyspepsia.

The ROME IV criteria further divide FD (functional dyspepsia) into two types (XX):

Postprandial distress syndrome
Bothersome postprandial fullness or early satiety severe enough to impact regular activities or finish a regular-size meal for three or more days per week in the past three months, with at least a 6-month history.

Epigastric pain syndrome
Bothersome epigastric pain or epigastric burning or more days per week in the past three months, with at least a 6-month history.

Note: Both require the absence of evidence of organic, systemic, or metabolic disease that is likely to explain the symptoms on routine investigations (including at upper endoscopy).

5. Mimics of functional dyspepsia.

Dyspepsia is extremely common; Many organic diseases can cause dyspepsia with symptoms identical to functional dyspepsia.

The most prevalent causes include:

  • Chronic gastritis and H. pylori infection.
  • Peptic ulcer disease.
  • Gastroesophageal reflux disease (GERD) or chronic acid reflux.
  • Food intolerances such as lactose intolerances and FODMAP intolerance.
  • Gastroparesis.
  • Irritable bowel syndrome: The overlap between IBS and FD is widespread; about 13-87% of the patients share the features of both diseases at the same time (reference).

The complete list of possible causes of dyspepsia (mimics of FD) are in the table below (reference):

Functional dyspepsia
Dyspepsia caused by structural or biochemical disease
Peptic ulcer disease
Gastroesophageal reflux disease (GERD)
Biliary pain
Chronic abdominal wall pain
Gastric or esophageal cancer
Carbohydrate malabsorption
Medications (including potassium supplements, digitalis, iron, theophylline, oral antibiotics [especially ampicillin and erythromycin], nonsteroidal anti-inflammatory drugs [NSAIDs], glucocorticoids, niacin, gemfibrozil, narcotics, colchicine, quinidine, estrogens, levodopa)
Infiltrative diseases of the stomach (e.g., Crohn’s disease, sarcoidosis)
Metabolic disturbances (hypercalcemia, hyperkalemia)
Hepatocellular carcinoma
Ischemic bowel disease, celiac artery compression syndrome, superior mesenteric artery syndrome
Systemic disorders (diabetes mellitus, thyroid, and parathyroid disorders, connective tissue disease)
Intestinal parasites (GiardiaStrongyloides)
Abdominal cancer, especially pancreatic cancer

6. Treatment

The treatments of functional dyspepsia improve most of its symptoms. However, no treatment provides a permanent cure for FD.

A. Don’t Overthink it.

Patients with a functional gut disease like functional dyspepsia are more likely to be stressed and anxious.

Functional dyspepsia is a benign medical condition that doesn’t lead to severe complications.

Overthinking and expecting the worst scenario increases the symptoms of functional dyspepsia.

B. Diet.

  • Eat smaller meals.
  • Avoid high-fat foods (high fat intake slows gastric emptying and worsens FD).
  • Some evidence suggests that Low FODMAP diet improves functional dyspepsia with bloating and IBS symptoms.
  • Avoid spicy foods.
  • Avoid carbonated drinks.
  • Avoid fried foods.

C. Acid-reducing medications.

Acid-reducing medications are particularly effective in the epigastric pain subtype of functional dyspepsia.

The most effective acid-suppressive agents are Proton Pump Inhibitors (PPIs) as omeprazole, Esomeprazole, and Dexlanzoprazole. Others include H2 blockers (as famotidine).

Your doctor may prescribe a PPI for four weeks or more. Don’t use PPIs for more extended periods unless prescribed by your doctor.

D. Prokinetics.

Prokinetic medications regulate the motility of your stomach and digestive system.

Prokinetics are particularly effective with postprandial distress syndrome (a subtype of functional dyspepsia.

Examples include Domperidone, metoclopramide, and ondansetron.

E. medications that relax stomach fundus.

Cisapride is a medication that relaxes the stomach muscle. As a result, it improves symptoms when traditional prokinetics are ineffective. Other options include Buspirone and Iberogast.

F. Antidepressants.

As we explained before, stress, depression, and anxiety plays a significant role in functional dyspepsia.

If the previous treatment is ineffective, Your doctor may prescribe a small dose of Tricyclic Antidepressant (TCA) such as amitryptiline.

G. Other treatments:

Other potentially helpful treatments of functional dyspepsia include Rifaximin (locally active gut antibiotic) and psychotherapy.

Rifaximin may help fight the harmful gut bacteria that cause disturbances in the gut microbiome.

Psychotherapy such as cognitive behavioral therapy can be tried. However, the evidence is still limited.

The usefulness of therapies for functional dyspepsia (reference):

TherapyFunctional dyspepsia subtypes
Epigastric pain syndromePostprandial distress syndrome
Acid suppression+++
Fundic relaxors+
Tricyclic antidepressants+++
Psychological therapy++

[-] → NOT effective

[+] → Mildly effective.

[++] → Very effective.

When to see a doctor (red flags):

  • Age of onset above 60.
  • Unintentional weight loss
  • Dysphagia (Difficult swallowing).
  • Odynophagia (pain during swallowing).
  • Unexplained iron deficiency anemia 
  • Persistent vomiting
  • Palpable mass or lymphadenopathy
  • Family history of upper gastrointestinal cancer.