Dyspepsia refers to chronic or recurrent upper gastrointestinal (GI) symptoms originating from the gastroduodenal region with a significant impact on patients' lives. Functional dyspepsia comprises the diagnostic categories of epigastric pain syndrome (EPS) with epigastric pain or burning and postprandial distress syndrome (PDS) with meal-related fullness or early satiation, which are unexplained after routine investigation including upper GI endoscopy 2. Despite the common occurrence of FD in up to 15% of the general population, the underlying pathophysiology remains unclear and no treatments of proven efficacy are available in Europe for this condition. Our group has demonstrated increased duodenal mucosal permeability and low-grade inflammation in FD patients, correlating with meal-related symptoms. The causes of the barrier defect and immune activation are unknown but candidates include psychological stress, luminal food components, (bile) acid and microbiota. The symptoms most closely associated with increased eosinophil counts in the duodenum are early satiation and postprandial fullness, which are typical PDS symptoms, and which are also associated with impaired gastric accommodation to meal ingestion and delayed gastric emptying. Previously the efficacy of the Kampo medicine Rikkunshito (TJ-43) has been shown in FD. The exact mode of action remains to be determined. Previous studies have provided mechanistic evidence that rikkunshito is able to improve gastric accommodation, improve food intake and enhance circulating levels of the orexigenic gut peptide ghrelin. The aim of this study is to evaluate the efficacy of Rikkunshito in comparison to placebo in PDS patients recruited from primary care in Belgium, and to evaluate whether this is associated with changes in duodenal mucosal low-grade inflammation.