The evidence-based epidemiology of HCV-associated kidney disease.

Novel information supports a definite link between hepatitis C virus (HCV) infection and chronic kidney disease (CKD) in the general population. HCV is associated with a large spectrum of histopathological lesions in both native and transplanted kidneys. Kidney disease is probably uncommon in HCV-infected patients even if its exact frequency remains unknown. The most common HCV-associated nephropathy is type I membranoproliferative glomerulonephritis, usually in the context of type II mixed cryoglobulinemia. Controversial information exists on the relationship between positive HCV serology and CKD but several surveys at population-based level suggest that infection with HCV per se is associated with an increased risk of having or developing renal insufficiency or proteinuria. According to a novel meta-analysis of observational studies (4 clinical studies, 93,919 unique individuals), positive HCV serology was an independent and significant risk factor for proteinuria; the summary estimate for adjusted relative risk is 1.55 with a 95% confidence interval (CI) of 1.14; 2.12, p = 0.0001 (random-effects model). The mechanisms of these associations appear complex, but both viral and non-viral processes have been implicated. Prospective studies are needed to fully characterize the exact impact of chronic HCV infection on kidney function trajectories over time.