Diagnosis and treatment of osteoporosis in chronic renal disease.

Osteoporosis is the most prevalent metabolic bone disease leading to low-trauma (fragility) fractures worldwide. There is no reason why osteoporosis, as defined by different criteria, cannot accompany the derangements in bone metabolism that characterize chronic kidney disease (CKD). In fact, osteoporosis could and should be included in the broad characterization of CKD-mineral and bone disorder (CKD-MBD), as recently proposed by the Kidney Disease: Improving Global Outcomes working group. The pathophysiology leading to osteoporosis or CKD-MBD shares many common yet distinctly different pathways. Both pathways may lead to impairment of bone strength and low-trauma fractures. The challenge for clinical practice is how to discriminate between osteoporosis and CKD-MBD in fracturing patients. There is agreement that in the absence of aberrant biochemical tests suggesting CKD-MBD in stages 1 through 3 CKD, osteoporosis can be diagnosed using the World Health Organization criteria or development of low-trauma fractures. The distinction between osteoporosis and CKD-MBD becomes more difficult in stages 4 and 5 through 5D CKD. In fracturing patients with these levels of severe CKD, careful biochemical assessment of bone turnover markers and, in selected cases, bone biopsy is needed to eliminate CKD-MBD and to diagnose osteoporosis by exclusion. In stages 1 through 3 CKD, the current registered osteoporosis pharmacologic therapies can be used to treat osteoporosis. In stage 4, 5, and 5D these agents can be considered off-label, but only after very careful considerations and only in fracturing patients without CKD-MBD. We need better noninvasive means of discriminating among all these metabolic bone diseases and prospective data to guide us to the use of agents that alter bone remodeling in high-risk patients with more severe CKD.