Effects of synbiotic treatment on serum level of p-cresol in haemodialysis patients: a preliminary study

Background. para-Cresol, which is present in the blood mainly as p-cresyl sulphate, is a protein-bound uraemic toxin that is produced in the intestine by certain intestinal bacteria, and its production is affected by various intestinal environmental factors. Patients with end-stage renal disease who are undergoing haemodialysis (HD) often have defective bowel function leading to abnormal defecation. Since treatment with synbiotics (SYN), which are a combination of probiotics and prebiotics, is reported to improve bowel habit, we examined the effects of SYN on the serum p-cresol level in HD patients. Methods. Nine HD patients received SYN (Lactobacillus casei strain Shirota and Bifidobacterium breve strain Yakult as probiotics and galacto-oligosaccharides as prebiotics) three times a day for 2 weeks. The duration of the study was 4 weeks (2 weeks of pretreatment observation and 2 weeks of treatment). The subjects were asked to complete a questionnaire about their bowel habits (defecation frequency, stool quantity, stool form and ease of defecation) during the study period. Serum p-cresol levels before and after SYN treatment were determined. Results. According to the questionnaire conducted during the pretreatment observation period, HD patients with a high serum p-cresol level tended to have hard stools with difficulty in defecation. With SYN treatment, stool quantity increased significantly and hard, muddy or soft stools tended to be replaced by normal ones. The serum p-cresol level also decreased significantly. Conclusions. It was found that uraemic toxin, p-cresol, was associated with constipation and that SYN treatment resulted in normalization of bowel habits and a decrease of serum p-cresol levels in HD patients. Therefore, SYN treatment may be anticipated to reduce the toxic effect of p-cresol in HD patients.