Serum Uric Acid Levels and Renal Damage in Hyperuricemic Hypertensive Patients Treated With Renin–Angiotensin System Blockers

Background A correlation between hyperuricemia and renal target organ damage (TOD) was shown in hypertensive patients, locally mediated by the activation of renin–angiotensin system (RAS). We investigated whether high serum uric acid (UA) levels could negatively affect tubulointerstitial damage in hyperuricemic essential hypertensive patients with normal renal function, on treatment with RAS-blocking drugs. Methods We studied 40 patients with World Health Organization stage I–II essential hypertension, 9 with high serum UA levels (hyperuricemic group) and 31 with normal serum UA levels (normouricemic group, either normouricemics, n = 15, or formerly hyperuricemics in chronic allopurinol treatment, n = 16). All patients were on RAS-blocking drugs (either angiotensin-converting enzyme inhibitors or angiotensin II receptors blockers). Evaluation of renal TOD included urinary albumin excretion (UAE), Doppler ultrasound renal resistive index (RRI) and renal volume-to-resistive index ratio (RV/RRI) measurements. Results Hyperuricemics had significantly higher RRI and lower RV/RRI values than normouricemics. Creatinine clearance and UAE were similar between groups. Linear regression analysis showed that RV/RRI values were inversely related to serum UA levels (r = −0.57, P < 0.01). The logistic regression analysis selected serum UA as an independent predictor of decreased RV/RRI (odds ratio 4.45, 95% CI 1.47–13.45, P = 0.01). Conclusions In hyperuricemic hypertensives normal serum UA levels are associated with normal RV/RRI, integrated marker of tubulointerstitial damage and renal arteriolopathy, independently of RAS activation.