New Recommendations on CKD Related Mineral and Bone Disorder (CKD-MBD)

New York, NY (2007-01-04)

There have been numerous observational studies recently published that show a clear association between the physiologic alterations in mineral homeostasis, vitamin D and bone metabolism, and cardiovascular function that occur in CKD. The descriptive term that we frequently use to discuss this group of related abnormalities is renal osteodystrophy. However, the literal interpretation of renal osteodystrophy is a progressive degeneration of bone due to inadequate nourishment. While the altered bone metabolism and progressive bone disease that occurs in CKD is a critical part of this syndrome, it is but one component of this inter-related group of abnormalities. To properly evaluate and determine a treatment plan for our patients with CKD, it is essential that we simultaneously consider all of the components of this disorder. The adoption of a more inclusive name with a clear definition based on readily available clinical parameters would promote clarity in how clinicians communicate about, evaluate and treat the systemic disorder of mineral and bone metabolism that is prevalent in CKD.

In September, 2006, Kidney Disease: Improving Global Outcomes (KDIGO) sponsored a Controversies Conference on the Definition, Evaluation, and Classification of Renal Osteodystrophy. 1 This international group of 70 physicians, representing 21 countries, made a number of recommendations on the descriptive nomenclature for disturbances of bone and mineral metabolism in CKD. The principal recommendation from the conference was that the terminology used to describe the bone and mineral abnormalities associated with CKD should be refined. Specifically, the term renal osteodystrophy (ROD) should be used exclusively to describe the alterations in bone morphology that occur in patients with CKD based on histologic examination of a bone biopsy. The clinical, biochemical, and imaging abnormalities that have previously been identified as correlates of ROD should be defined more broadly as a clinical entity or syndrome to be called Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). The definition of CKD-MBD is:

A systemic disorder of mineral and bone metabolism due to CKD manifested by either one or a combination of the following:

  • Abnormalities of calcium, phosphorus, PTH, or vitamin D metabolism
  • Abnormalities in bone turnover, mineralization, volume, linear growth, or strength
  • Vascular or other soft tissue calcification

The participants in the KDIGO Controversies Conference also made recommendations on what parameters should be evaluated as part of the initial assessment of Mineral and Bone Disorder. The initial evaluation should include measurement of serum PTH, calcium (either ionized or total corrected for albumin), phosphorus, alkaline phosphatase (total or bone-specific), and bicarbonate concentrations. Imaging for soft tissue calcification should also be accomplished. A lateral abdominal X-ray can be used as the initial screening test for calcification. A positive finding of aortic calcification on an abdominal radiograph, may warrant further semi-quantitative evaluation by CT scan. If there are inconsistencies in the biochemical markers (e.g. high PTH but low alkaline phosphatases), unexplained bone pain, or unexplained fractures, a bone biopsy would be indicated. Additional tests to assess linear growth rate are needed in children with CKD.

References:

  1. Moe S, Drueke T, Cunningham J, Goodman W, Martin K, Olgaard K, Ott S,
    Sprague S, Lameire N, Eknoyan G: Definition, evaluation, and classification of
    renal osteodystrophy: a position statement from Kidney Disease: Improving
    Global Outcomes (KDIGO). Kidney Int 69:1945-1953, 2006