TABLE 5.

Results of the synthetic knowledge synthesis in FD research.

Theme	Color	Representative author keywords	Prevailing sub-categories
H. pylori infection	Red	Gastric cancer, gastropanel, gastrin-17, cytotoxin associated gene A (CagA), vacuolating cytotoxin, duodenal ulcer promoting gene (dupA), malignancy, gastric ulcer, duodenal ulcer, PPI, antacids, rebamipide, reflux esophagitis, quadruple therapy, triple therapy	The association between H. pylori and the development of noncardia gastric cancer and peptic ulcer disease; the molecular basis by which H. pylori induces gastric cancer; diagnostic tests for H. pylori infection; antibiotic eradication of H. pylori infection; screening and treatment for H. pylori infection; the link between gastroesophageal reflux disease (GERD) and H. pylori; the involvement of H. pylori in FD
Pathophysiological mechanisms of FD	Green	Duodenal inflammation, mast cells, eosinophils, GNB3, interleukin (IL)-17F, IL-10, melatonin, gastric motility, impaired gastric accommodation, gastric slow waves, leptin, peptide YY, cholecystokinin, glucagon-like peptide 1, motilin, gastric emptying, tegaserod, itopride, prokinetics, acotiamide, gut microbiota, small intestinal bacterial overgrowth (SIBO), the interstitial cells of Cajal (ICCs), visceral hypersensitivity, functional magnetic resonance imaging (fMRI), bile acids, brain-gut axis, enteric nervous system, vagal nerve, food allergy, dopamine, acupuncture, electroacupuncture	Neuronal mechanisms of visceral hypersensitivity in FD; abnormal visceral pain signaling in FD; subtle infiltration and activation of eosinophils and mast cells; dysregulation of the gut-brain axis in FD; neuropeptides in the pathogenesis and treatment of FD; dysregulation of enteroendocrine cells signaling in FD; pathophysiologic involvement of ICCs in FD; bile acid alterations as an important determinant in FD etiopathogenesis; food allergy as stimulants in FD symptoms; brain network alterations in FD; acupuncture treatment of FD
Extraintestinal co-morbidities and overlap syndromes associated with FD	Yellow	Migraine, chronic pelvic pain, fibromyalgia, chronic fatigue, endometriosis depression, sleep disorders, insomnia, anxiety, antidepressants, posttraumatic stress disorder, alexithymia, post-cholecystectomy syndrome, aerophagia, Crohn’s disease, celiac disease, lactose intolerance, GERD, IBS, functional constipation	The extraintestinal co-morbidities of FD, many of which are chronic painful disorders; psychological co-morbidities associated with FD; FGID overlap syndrome; FD patients with overlapping GERD
Herbal medicine in FD	Light blue; pink	Iberogast (STW5), Iberis amara, Mentha piperita, Glycyrrhiza glabra, Angelica archangelica, Carum carvi, Chelidonium majus, carraway oil, peppermint oil	Phytomedical treatment for FD
Diabetic gastroparesis	Dark blue	Glucose tolerance, type 2 diabetes mellitus, type 1 diabetes mellitus, post-prandial hyperglycemia, hyperinsulinemia, hypertriglyceridaemia, and insulin resistance, nonalcoholic fatty liver disease, high-fat meal, oxidative stress, nitric-oxide, adipose tissue, exercise, prolonged sitting	The overlap of symptoms in FD and gastroparesis; pathophysiology of FD and gastroparesis and overlap
Dietary factors in FD	Purple	Body mass index (BMI), alcohol, FODMAPs (fermentable oligo-, di-, and monosaccharides and polyols), gluten wheat	Mechanisms underlying food- and eating-induced symptoms of FD; diet-focused approach to treating FD