Functional dyspepsia (FD) refers to one or a group of symptoms originating from the gastroduodenal region that cannot be explained by organic, systemic, or metabolic diseases. The primary symptoms include postprandial fullness, early satiety, epigastric pain, and burning sensations, with other possible symptoms such as abdominal bloating, belching, nausea, and emesis.
Etiology and Pathogenesis
Multiple factors contribute to the development and progression of FD.
Gastroduodenal Motility Disorders
These are characterized by delayed gastric emptying and impaired gastric accommodation. Approximately 40% of FD patients exhibit delayed gastric emptying, with a significant reduction in the rate of solid food emptying. Nearly half of FD patients show impaired gastric accommodation.
Visceral Hypersensitivity
Hypersensitivity to mechanical distension in FD patients may be a key factor in symptoms such as postprandial pain, belching, nausea, and fullness. The heightened sensitivity to gastric distension after meals is significantly associated with the severity of postprandial symptoms.
Gastric Acid, Infection, and Dietary Factors
Gastric acid, infections, and dietary habits may play roles in FD pathogenesis. Some FD patients experience symptoms resembling peptic ulcers and respond well to acid-suppressing medications. Dietary factors and infections are also important triggers of FD.
The diverse symptoms of FD may be linked to different pathophysiological mechanisms, which are not entirely independent but rather interact with and influence each other. Central regulatory abnormalities contribute to gastrointestinal motility disorders and visceral hypersensitivity. Dysfunction in the "gut-brain axis," caused by multiple factors, is considered a crucial mechanism in the development of FD.
Clinical Manifestations
The onset is often gradual, presenting as a persistent or recurrent condition. Many patients report dietary or psychological triggers. Symptoms may vary over the course of the disease, with one or a group of symptoms predominating. The main symptoms include postprandial fullness, early satiety, epigastric pain, epigastric burning, belching, loss of appetite, nausea, and emesis.
Postprandial Fullness and Early Satiety
These symptoms are closely related to food intake. Postprandial fullness refers to a feeling of bloating after a normal meal, while early satiety describes a sensation of fullness shortly after beginning to eat, despite initial hunger.
Epigastric Pain
This is a common symptom that is often associated with food intake, presenting as postprandial pain, though it may also occur without a specific pattern. Some patients experience epigastric burning sensations.
Extragastrointestinal Manifestations
Many patients also report symptoms such as insomnia, anxiety, depression, headaches, and difficulty concentrating.
Diagnosis and Differential Diagnosis
The diagnosis of FD can be considered based on the following criteria:
- The presence of one or more of the following symptoms: postprandial fullness, early satiety, epigastric pain, or epigastric burning.
- A chronic course of symptoms that are persistent or recurrent (symptoms must have been present for at least 6 months, with the diagnostic criteria fulfilled in the last 3 months).
- Routine examinations, including upper gastrointestinal endoscopy, reveal no evidence of organic, systemic, or metabolic diseases to explain the symptoms.
FD patients can be classified into two subtypes based on specific symptoms:
- Postprandial Distress Syndrome (PDS): Characterized by postprandial fullness and/or early satiety, with symptoms triggered and persisting after meals.
- Epigastric Pain Syndrome (EPS): Characterized by epigastric pain and/or burning sensations, which are not clearly related to food intake.
Overlap between these two subtypes is common in clinical practice.
Diseases that need to be differentiated from FD include:
- Various organic diseases of the stomach and duodenum, such as peptic ulcers and gastric cancer.
- Hepatobiliary and pancreatic diseases, such as chronic viral hepatitis, chronic cholecystitis, and chronic pancreatitis.
- Systemic or other conditions that may cause similar upper gastrointestinal symptoms, such as diabetes, kidney disease, rheumatic and autoimmune diseases, and psychiatric or neurological disorders.
- Dyspepsia caused by nonsteroidal anti-inflammatory drugs (NSAIDs) or other medications.
- Other functional gastrointestinal disorders and motility disorders, such as gastroesophageal reflux disease (GERD) and irritable bowel syndrome (IBS).
Treatment
The treatment aims to alleviate symptoms and improve the quality of life for patients.
General Management
Providing reassurance, educational guidance, and open communication is essential for FD patients. Clear information about the diagnosis should be conveyed to help patients understand that FD is not life-threatening, thereby alleviating their fears and doubts. Efforts to gain patient cooperation and enhance treatment adherence are important. Patients are encouraged to develop healthy lifestyle and dietary habits, reduce the intake of irritant and gas-producing foods, and avoid high-fat diets.
Pharmacological Treatment
Acid-Suppressing Medications
Proton pump inhibitors (PPIs) or H2 receptor antagonists (H2RAs) are effective in controlling FD symptoms and can be considered the first-line treatment for EPS. Both H2RAs, standard-dose PPIs, and low-dose PPIs can significantly improve FD symptoms. However, long-term use of high-dose PPIs does not enhance efficacy and may increase the risk of adverse drug reactions.
Prokinetic Agents
Prokinetic drugs are an effective treatment option for PDS and can alleviate symptoms in some FD patients. Medications such as cinitapride, itopride, mosapride, domperidone, and trimebutine improve gastrointestinal motility through various mechanisms, relieving dyspeptic symptoms and enhancing the quality of life.
Digestive Enzyme Supplements
Digestive enzyme preparations can serve as adjunctive therapy for dyspepsia, alleviating symptoms such as upper abdominal bloating and poor appetite, which are associated with meals.
Neuromodulators
Neuromodulators are suitable for patients with poor responses to conventional treatments and significant anxiety or depressive symptoms. Commonly used medications include tricyclic antidepressants, norepinephrine reuptake inhibitors, and selective serotonin reuptake inhibitors (SSRIs). These should be initiated at low doses, with attention to potential adverse effects. The choice of neuromodulator may depend on the FD subtype and the presence of psychological disorders.
Psychological Therapy
Psychological therapy can be used as a supplementary approach for patients with severe symptoms and poor responses to pharmacological treatment. It helps patients develop positive coping strategies, adjust their perception of symptoms, and reduce symptom-related focus. This, in turn, can alleviate FD symptoms and improve quality of life.
Prognosis
FD symptoms can recur intermittently and may affect quality of life, but the condition generally follows a benign course.