Background Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders characterized by recurrent abdominal pain associated with defecation or a change in bowel habits. Leading to significant negative effect on patients’ quality of life and huge financial burden to health system, the management of IBS is a great challenge. Probiotics are considered as an effective therapy; however, in a lack of high-quality evidence of efficacy, no strain- and dose-specific probiotics were recommended in clinical guidelines. This study aims to evaluate the efficacy of the Bifidobacterium quadruple viable tablet in the treatment of IBS-D. Methods/design A multicenter randomized controlled trial will be performed in fourteen hospitals. A total of three hundred patients who fulfill the eligibility criteria will be stratified divided into an experimental group and a control group randomly in a ratio of 1:1. The experimental group is treated with the Bifidobacterium quadruple viable tablet while the control group is treated with placebo. All the patients will receive a 4-week treatment and a 2-week follow-up. The primary outcome is the effectiveness in improving abdominal pain and stool consistency; the secondary outcome includes evaluation of overall symptom relief, frequency of defecation, bloating, urgency of defecation, remedial medication, score of IBS-QOL, and changes of microbiota and metabonomics. Physical examination, vital signs, laboratory tests, adverse events, and concomitant medication will be taken into account for intervention safety assessment during the trial. Discussion This multicenter randomized controlled trial may provide high-quality evidence on the efficacy of the Bifidobacterium quadruple viable tablet for IBS-D on both physical and mental dimensions in China. To fill the gap of previous probiotic intervention studies, in addition, this study will also present safety assessment which will be a significant emphasis. Trial registration ChiCTR1800017721. Registered on 10 August 2018.

Objectives: In China, four symptoms of functional gastrointestinal disorders, postprandial fullness, early satiety, bloating, and abdominal distension are commonly and interchangeably expressed as a single chief complaint, "Zhang". In this study we aimed to explore the most efficient method of determining the characteristics of symptoms in such patients.Methods: Consecutive patients with the chief complaint of abdominal "Zhang" from December 2017 to June 2018 were included. Their symptom patterns were determined by face-to-face interviews. Patients with a single symptom (postprandial fullness, early satiety, bloating, or abdominal distension) completed the questionnaire assessing their understanding of the symptoms using three methods including concept terms, pictograms, and verbal descriptions.Results: A total of 230 patients (121 men, 109 women; mean age 43.7 ± 12.6 y) were included. Verbal descriptions were most applicable to identify patients' symptom patterns, followed by concept terms and pictograms. Early satiety was the most difficult to identify (20.9% agreement between patient's understanding and doctor's diagnosis by using concept term), whereas fullness and bloating had apparently higher recognition (70.7% and 72.1% by concept terms). Elder patients (>60 y) and those with more frequent symptom attacks (≥once daily) showed relatively poorer understanding of the symptoms. Conclusions:Early satiety is poorly identified by patients. Existing pictograms fail to show comprehension-improving features in a Chinese cultural setting. Verbal descriptions may be the best option for diagnosing abdominal "Zhang". More caution is required during the inquiry of medical history from elder patients with frequent symptom attacks.