What is functional dyspepsia?

What is Functional Dyspepsia?

Functional dyspepsia (FD) is a disorder of gut-brain interaction characterized by bothersome epigastric pain, burning, early satiation, or postprandial fullness lasting more than 8 weeks, without any structural or biochemical abnormality found on investigation that explains the symptoms. 1

Core Definition and Diagnostic Criteria

FD requires the presence of one or more of four cardinal symptoms that are bothersome enough to affect daily activities: 1

• Epigastric pain (upper central abdominal pain)
• Epigastric burning
• Early satiation (inability to finish a normal-sized meal)
• Postprandial fullness (uncomfortable fullness after eating)

These symptoms must persist for at least 8 weeks according to the Rome IV clinical criteria used in routine practice, though the formal Rome IV research criteria require 3 months of symptoms with onset at least 6 months prior. 1, 2 Critically, appropriate investigation (typically endoscopy) must show no structural disease such as peptic ulcer, cancer, or esophagitis that would explain the symptoms. 1

Prevalence and Clinical Impact

• FD affects approximately 7% of individuals in the community, making it one of the most common gastrointestinal disorders. 1
• The annual prevalence of dyspepsia overall in Western countries is approximately 25%, with most patients ultimately having FD as the underlying cause after investigation. 1
• FD accounts for 2-5% of all primary care consultations. 1

Clinical Subtypes

The Rome IV criteria recognize two overlapping subtypes of FD: 2, 3

• Epigastric Pain Syndrome (EPS): Predominant symptom is bothersome epigastric pain or burning occurring at least 1 day per week
• Postprandial Distress Syndrome (PDS): Predominant symptoms are bothersome postprandial fullness or early satiation occurring at least 3 days per week

These subtypes frequently overlap in the same patient, and the distinction has limited therapeutic implications in routine practice. 1, 3

Key Distinguishing Features from GERD

The critical distinction between FD and gastroesophageal reflux disease (GERD) is the predominant symptom: 1, 4

• In FD, the predominant symptom is epigastric pain or discomfort centered in the upper abdomen
• In GERD, the predominant symptom is heartburn (burning sensation starting in the epigastrium but radiating to the chest) or acid regurgitation occurring more than once weekly 1, 4

However, there is substantial symptom overlap in clinical practice: 63-66% of patients with heartburn also have coexisting epigastric pain, and approximately one-third of FD patients have coexisting GERD symptoms. 1, 4 The key is to ask patients to identify their single most bothersome or predominant symptom to guide diagnosis and treatment. 4

Pathophysiology: A Disorder of Gut-Brain Interaction

FD should be explained to patients as a disorder of gut-brain interaction (DGBI), not a psychological condition, but rather a condition where multiple mechanisms along the gut-brain axis malfunction: 1

• Delayed gastric emptying (present in ~30% of patients) 3
• Impaired gastric accommodation (inability of the stomach to relax properly after eating, particularly important in PDS) 3
• Visceral hypersensitivity (heightened sensitivity to normal gastric activities) 3, 5
• Duodenal mucosal alterations including low-grade inflammation and impaired barrier function 3
• Post-infectious changes (approximately 10% develop FD after acute gastroenteritis with pathogens including Norovirus, Giardia, Salmonella, E. coli O157, and Campylobacter) 1
• Psychological factors including stress, anxiety, and depression 3, 5

Common Overlapping Conditions

FD frequently coexists with other functional disorders: 1

• Irritable bowel syndrome (IBS) overlaps in up to 50% of FD patients. The key distinction: in FD, abdominal pain is unrelated to defecation, whereas in IBS, pain is related to bowel movements. 1
• Other functional bowel disorders (functional constipation, functional diarrhea, functional bloating) can also overlap. 1
• Eating disorders or disordered eating behavior are increasingly recognized in FD patients. 1

What FD is NOT

FD excludes several important conditions: 1, 2

• Patients with predominant heartburn should be classified as GERD, not FD 1, 4
• Persistent vomiting suggests another disorder and requires investigation 2
• Alarm features exclude a diagnosis of FD until investigated: unintentional weight loss, dysphagia, rectal bleeding, family history of gastric/esophageal cancer 2
• Any structural abnormality on endoscopy (peptic ulcer, cancer, esophagitis) means the patient does not have FD by definition 1

Clinical Pitfalls to Avoid

• Do not diagnose FD in patients ≥55-60 years with new-onset symptoms without appropriate investigation, as malignancy must be excluded. 1
• Do not overlook H. pylori testing, as eradication provides modest benefit (6-14% therapeutic gain) and prevents future peptic ulcer disease and gastric cancer. 1, 6
• Do not assume all upper abdominal symptoms are FD—always consider medication-induced dyspepsia, particularly from NSAIDs and opioids. 1
• Do not dismiss the diagnosis as "all in the patient's head"—FD has demonstrable physiological abnormalities and significantly impairs quality of life. 1