Urinary indoxyl sulfate is a clinical factor that affects the progression of renal failure

We recently demonstrated that indoxyl sulfate is a stimulating factor for t he progression of chronic renal failure (CRF). In this study we determined whether the urine or serum levels of indoxyl sulfate are related to the pro gression rate of CRF in undialyzed uremic patients. Fifty-five CRF patients with a serum creatinine of >2 mg/dl who had not been treated with an oral sorbent (AST-120) were randomly enrolled in the study, We measured the seru m and urine levels of indoxyl sulfate, and estimated the recent progression rate of CRF as the slope of the reciprocal serum creatinine versus time (1 /S-Cr-time) plot, The mean urinary amount of indoxyl sulfate in the patient s was 60 mg/day. Those with indoxyl sulfate urine levels of > 60 mg/day had a significantly faster progression rate of CRF than those with < 60 mg/day . Especially, those patients with indoxyl sulfate urine levels of >90 mg/da y had the highest CRF progression rate and those with indoxyl sulfate urine levels of <30 mg/day had the slowest CRF progression rate, Urinary indoxyl sulfate had a significantly negative correlation with the slope of the 1/S -Cr-time plot. However, the serum level of indoxyl sulfate or the ratio of serum indoxyl sulfate to creatinine was not significantly correlated with t he slope of the 1/S-Cr-time plot. In conclusion, high urine levels of indox yl sulfate are related with a rapid progression of CRF in undialyzed uremic patients, Thus, urinary indoxyl sulfate is one of the clinical factors tha t affect CRF progression.