Mild hyperuricemia and subclinical renal damage in untreated primary hypertension

Background: Subclinical renal damage and hyperuricemia are not uncommon in patients with primary hypertension. Whether mild hyperuricemia reflects a subclinical impairment of renal function or contributes to its development is currently debated. We investigated the relationship between serum uric-acid levels and the occurrence of early signs of kidney damage. Methods: Four hundred eighteen patients with primary hypertension were studied. Albuminuria was measured as the albumin-to-creatinine ratio, and creatinine clearance was estimated by the formula of Cockcroft and Gault. Interlobar resistive index and renal abnormalities, ie, the renal volume-to-resistive index ratio, were evaluated by renal Doppler and ultrasound. Results: Uric acid was directly related to resistive index (P =.007) in women and to albuminuria (P =.04) in men, and was inversely related to the renal volume-to-resistive index ratio in both men (P =.005) and women (P =.02). Patients with uric-acid levels above the median showed a higher prevalence of microalbuminuria (14% nu 7%, P =.012) and of renal abnormalities (41% nu 33%, P =.007). Moreover, when creatinine clearance was taken as a covariate, patients with increased uric-acid levels showed higher albuminuria and resistive indices, and a lower renal volume-to-resistive index ratio. Even after adjustment for several risk factors, each standard deviation increase in serum uric acid entailed a 69% higher risk of microalbuminuria, and a 39% greater risk of ultrasound detectable renal abnormalities. Conclusions: Mild hyperuricemia is associated with early signs of renal damage, ie, microalbuminuria and ultrasound-detectable abnormalities, regardless of the glomerular filtration rate in primary hypertension. Am J Hypertens 2007;20:1276-1282 (c) 2007 American Journal of Hypertension, Ltd.