Vascular calcifications in uremia: old concepts and new insights.

The annual mortality rate in uremic patients, corrected for age, sex, and race, is significantly higher than in the general population. This is primarily due to cardiovascular events. Vascular calcifications play a vital role in the development of cardiovascular morbidity and subsequent increased mortality. Vascular calcification affects both vascular intima and media layers and its mechanism remains poorly understood. Over the last few years it has been shown that, in addition to traditional cardiovascular risk factors, disturbances in mineral metabolism in the uremic milieu, calcium-containing phosphate binders, and vitamin D treatment of secondary hyperparathyroidism may contribute to the pathogenesis of vascular calcifications. Other uremia-related risk factors (e.g.increased oxidized low-density lipoprotein cholesterol, uremic toxins, increased oxidative stress, dialysis and dialysate-related factors, hemodynamic overload, hyperhomocysteinemia) may also play a role. In uremic patients, apart from these facilitating factors, decreased levels of endogenous calcification inhibitors such as fetuin-Amatrix Gla protein, osteoprotegerin, and osteopontin have also been associated with increased calcium-phosphate precipitation in extraskeletal tissues. Finally, vascular calcification is the outcome of the active and dynamic balance of procalcifying and anticalcifying influences. For the prevention and treatment of vascular calcifications, it is essential to avoid treatment modalities that lead to calcium overload, achieve good metabolic control, and optimize dialysis.