by Felix C.

Describe the CKD mineral and bone disorder (CKD-MBD)

  • Definitions:

    • CKD-MBD refers to abnormalities in mineral and/or bone metabolism in CKD.

    • Renal osteodystrophy refers specifically to issues with bone metabolism due to CKD.

  • Pathophysiology

    • CKD results in hypocalcemia via different mechanisms.

      • ↓ Renal excretion of phosphate → hyperphosphatemia → calcium phosphate precipitation in tissues → ↓ Ca2+

      • ↓ Renal hydroxylation of vitamin D → ↓ 1,25-dihydroxyvitamin D → ↓ intestinal Ca2+ absorption → ↓ Ca2+

    • Chronically decreased calcium levels can cause secondary hyperparathyroidism, which can progress to tertiary hyperparathyroidism.

  • Histological classification

    • Secondary hyperparathyroidism: high turnover bone disease or osteitis fibrosa cystica (metabolic bone disease)

    • Osteomalacia: defective bone mineralization

    • Mixed uremic bone disease: secondary hyperparathyroidism with osteomalacia

    • Adynamic bone disease: decreased bone formation without osteomalacia

  • Clinical features (may be asymptomatic initially)

    • Musculoskeletal

      • Fractures

      • Bone and periarticular pain

      • Muscular weakness and pain

    • Extraskeletal

      • Focal vascular calcification (atherosclerotic plaques)

      • Diffuse vascular calcification (medial calcific sclerosis and calcific uremic arteriolopathy)

  • Diagnostics [31]

    • Laboratory studies: frequent monitoring with a mineral and bone disorder panel

    • Imaging (not routinely indicated)

      • X-ray may show sclerotic changes (rugger jersey spine), brown tumors, and/or subperiosteal bone thinning.

      • Consider bone mineral density testing for patients with CKD category G3–G5.

  • Treatment (under specialist guidance): The goal is to normalize phosphate, calcium, and PTH levels. [30][31]

    • Treatment of hyperphosphatemia, e.g.:

      • Dietary phosphate restriction

      • Phosphate binders (e.g., sevelamer)

    • Treatment of hyperparathyroidism, e.g.:

      • Cholecalciferol or ergocalciferol supplementation for vitamin D deficiency or insufficiency

      • Calcitriol (not routinely recommended)

      • Calcimimetics (e.g., cinacalcet)

      • Parathyroidectomy (last-line therapy)


Felix C.


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