Correlation Between Indoxyl Sulfate in Chronic Kidney Disease and Olfactory Dysfunction

Olfactory dysfunction is prevalent among individuals with chronic kidney disease (CKD), with prevalence escalating alongside disease severity. The uremic toxin we observed in this study is Indoxyl sulfate (IS), a potent uremic toxin that markedly accumulates in the plasma of patients with chronic insufficiency. Olfactory damage may occur in the setting of neuronal damage due to renal failure.  27 patients, a total sample in this study with diagnosed chronic kidney disease within stage 5 on regular hemodialysis, were examined for indoxyl sulfate levels in blood plasma and then examined for their olfactory function using the Sniffin’ Sticks test. A correlation analysis was conducted between indoxyl sulfate levels and olfactory function test results in patients with CKD.  The Pearson correlation test revealed a strong, significant negative correlation between indoxyl sulfate levels and olfactory function (r = -0.613; p = 0.001). Additionally, correlations were found between indoxyl sulfate levels and each component of olfactory function: threshold value (r = -0.408; p = 0.035), discrimination (r = -0.807; p = 0.001), and identification (r = -0.703; p = 0.001). Olfactory function is compromised in individuals with chronic renal disease and correlates with the level of accumulation of the uremic toxin indoxyl sulfate.