Differences and Intersections in Renal Biopsy Findings in Patients with Asymptomatic Hyperuricemia and Gout

Abstract

The aim of this study is to establish the association between asymptomatic hyperuricemia and gout with morphological and immunofluorescent changes in the renal biopsy. A total of 64 patients, 46 with asymptomatic hyperuricemia and 18 with gout were included in this retrospective study. Renal biopsy findings, clinical and laboratory data were analyzed by using medical documentation. We did not find a significant difference in the distribution of chronic renal failure between the two groups. In the gout group, the proportion of patients with nephrolithiasis was higher (p <0.001), and the presence of erythrocyturia was more common (p = 0.047). The percentage of damaged glomeruli (p = 0.249) and the distribution of mesangial proliferation (p = 0.536) was similar in the groups. The proportion of patients with interstitial fibrosis > 50$% was significantly higher in the gout group (p = 0.032), but no difference was observed in the distribution of tubular atrophy > 50% (p = 0.183). In subjects not receiving urate-lowering therapy, serum uric acid levels were comparable in the different stages of tubular atrophy and interstitial fibrosis. We found that in both asymptomatic hyperuricemia and gout, there is a deposition of immune deposits subepithelially, subendothelially, in the mesangium and in the vessel walls. In gout, the kidneys are affected to a much greater extent. We consider that not only the increased serum uric acid is important, but also monosodium urate crystals deposited in the renal interstitium causing a chronic inflammatory process followed by fibrosis. We suggest that the activation of the innate immune system by soluble uric acid and crystals with the subsequent development of a proinflammatory state in the body has led to the activation of complement and deposition of immune deposits in the kidneys.