Intestinal bacteria-derived putrefactants in chronic renal failure

Background. Phenols and indoles are fermentation products and putrefactants of intestinal bacterial origin. They present a problem in chronic renal failure and hemodialysis patients because they accumulate in the body as uremic toxins. Methods. A comparative study was performed in groups of patients with chronic renal failure (CRF) before the initiation of dialysis, hemodialysis patients (HD), and healthy adults to investigate changes in intestinal flora and to measure the blood levels of uremic toxins. Results. The level of Escherichia coli was significantly increased in the CRF and HD groups compared with the healthy controls (P= 0.02, controls vs CRF before dialysis; P= 0.0014, controls vs HD). Fecal concentrations of phenol and scatole were most highly elevated in the HD group, and the difference between the CRF and HD groups was significant (P= 0.02 for phenol; P= 0.01 for scatole). Serum concentrations of phenol, p-cresol, and indican were significantly elevated in the CRF group (P= 0.01; P= 0.008; and P < 0.0001 vs controls, respectively). For indican, a correlation was found between fecal and serum concentrations only in the HD group (correlation coefficient of 0.821; P= 0.04). In the CRF group, a correlation was obtained between the urine and serum concentrations of phenol and p-cresol (0.852, P= 0.01; 0.758, P= 0.02, respectively). A correlation was also found between the serum concentrations of indican and serum creatinine (SCr) (0.610; P= 0.004) and [beta]2-microglobulin ([beta]2-MG) (0.739; P= 0.005). Conclusions. An abnormal balance of intestinal bacterial flora and increased intestinal bacteria-derived putrefactants were observed in the CRF group. The increased concentration of toxins with renal sclerosing effects, such as indican, may contribute to further deterioration of renal function.