[CKD-MBD (Chronic Kidney Disease-Mineral and Bone Disorder). Bone metabolism in CKD-MBD]

"Abnormality in bone metabolism" is one of the three components that construct CKD-MBD besides "abnormality in laboratory examination" and "abnormality in soft tissue calcification". However, not all the bone metabolic disorders found in CKD patients are regarded as symptoms of CKD-MBD. Generally, bone metabolic abnormality in CKD-MBD is recognized as that caused by abnormality in systemic mineral metabolism associated with CKD. Bone metabolism in CKD-MBD displays wide spectrum. Conventionally, bone metabolism in CKD patients was classified into 5 categories according to two assessment axis, "bone cell activity" and "bone mineralization". Recently, a new system called "Turnover Mineralization-Volumec (TMV) classification" was advocated that applied cancellous bone volume as another major assessment axis. However, both the new and the old are totally dependent on histological findings, and therefore they are practically no use at bedside. It is highly desirable to establish new classification based on non-invasive study results and clinical outcomes.