Diagnosis and Treatment of CKD-MBD

Diagnostic Approach

• The American College of Physicians recommends monitoring serum levels of calcium, phosphate, PTH, and alkaline phosphatase activity beginning in CKD G3a 1
• The Kidney Disease: Improving Global Outcomes (KDIGO) guideline suggests frequency of monitoring should be based on CKD stage: CKD G3a-G3b, CKD G4, and CKD G5/G5D have different monitoring frequencies for calcium, phosphate, and PTH 1
• The National Kidney Foundation recommends that alkaline phosphatase activity should be monitored every 12 months in CKD G4-G5D, or more frequently with elevated PTH 1
• Treatment decisions should be based on trends in PTH levels rather than single values, according to the American College of Physicians 2
• Dual-energy X-ray absorptiometry (DXA) BMD testing is recommended for patients with CKD G3a-G5D if results will impact treatment decisions, as suggested by the American College of Physicians 2
• DXA BMD predicts fractures across the spectrum of CKD severity, including CKD G3a to G5D, according to the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 2
• Lateral abdominal radiograph can detect vascular calcification, and echocardiogram can detect valvular calcification, as recommended by the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 1
• Bone biopsy remains the gold standard for diagnosis and classification of renal osteodystrophy, according to the American College of Physicians 2

Treatment Approach

• The American College of Physicians recommends basing treatment on serial assessments of phosphate, calcium, and PTH levels, considered together 2
• Treatment choices should take into account potential adverse effects, such as antiresorptives exacerbating low bone turnover, and denosumab causing hypocalcemia, as suggested by the American College of Physicians 3, 4
• The Kidney Disease: Improving Global Outcomes (KDIGO) guideline suggests lowering elevated phosphate levels toward the normal range 2
• Focus treatment on patients with overt hyperphosphatemia rather than maintaining normal phosphate levels in non-dialysis patients, according to the American College of Physicians 3
• Consider dietary phosphate restriction, phosphate binders, and intensified dialysis for G5D patients, as recommended by the American College of Physicians 2
• Limit use of calcium-based phosphate binders in patients with hyperphosphatemia, according to the American College of Physicians 3
• Avoid hypercalcemia in all GFR categories of CKD, as suggested by the American College of Physicians 3
• Treat patients with PTH values that are progressively increasing or persistently above the upper limit of normal, according to the American College of Physicians 3
• Do not base treatment on a single elevated value, as recommended by the American College of Physicians 3
• For patients not on dialysis, avoid routine use of calcitriol or vitamin D analogues due to increased risk of hypercalcemia, according to the American College of Physicians 3
• For patients on dialysis, calcimimetics, calcitriol, and vitamin D analogues are acceptable first-line options, as suggested by the American College of Physicians 3
• Consider low-dose active vitamin D supplementation to help control PTH, according to the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 5
• Monitor for hypercalcemia when using vitamin D supplementation, as recommended by the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 5
• Treat metabolic acidosis to improve bone health by reducing bone resorption, according to the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 5

Monitoring and Follow-up

• Regularly assess response to therapy with laboratory monitoring of mineral metabolism parameters, as suggested by the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 5
• Continue monitoring BMD in patients receiving treatment for CKD-associated osteoporosis, according to the American College of Physicians 2
• Bone disease in CKD is complex with overlapping features of renal osteodystrophy and other forms of osteoporosis, as described by the Kidney Disease: Improving Global Outcomes (KDIGO) guideline 6, 7

Bone Mineral Density Assessment and Management in Chronic Kidney Disease

When to Perform DXA BMD Testing

• In adults with CKD stages 3–5 (eGFR < 60 mL/min/1.73 m²) at risk for osteoporosis, DXA BMD testing should be performed only if the results will influence treatment decisions, because hip BMD reliably predicts fractures across all CKD stages. KDIGO 2017 guideline supports this approach. 8

• DXA BMD is indicated in CKD G3a‑G5D patients who have biochemical evidence of CKD‑MBD (elevated intact PTH, abnormal serum calcium or phosphate). 8

• DXA BMD is also indicated in CKD G3a‑G5D patients with traditional osteoporosis risk factors (post‑menopausal status, men > 50 years, chronic glucocorticoid use). 8

• Testing should be limited to situations where low or declining BMD would lead to concrete interventions such as fall‑prevention programs or initiation of osteoporosis medication. 9

• The 2017 KDIGO guideline reversed the 2009 recommendation against routine BMD testing after prospective cohort studies showed that hip BMD predicts fractures in CKD patients with accuracy comparable to the general population. 8

Initial Biochemical Assessment Before DXA

• Prior to ordering DXA, obtain serum calcium, serum phosphate, and intact PTH to evaluate for CKD‑MBD. 8

• Measure 25‑hydroxyvitamin D to identify deficiency that may affect bone health and treatment planning. 10

• Treatment decisions should be based on trends in PTH over time, not on a single isolated value. 11

Interpreting DXA Results in CKD

• Hip BMD is the most reliable anatomical site for fracture prediction in CKD patients; multiple studies demonstrate a consistent association between low hip BMD and increased fracture risk across CKD stages G3a‑G5D. 8

• WHO T‑scores can be applied to CKD patients as they predict fracture risk similarly to the general population, including those on dialysis or with kidney transplants. 10

• A key limitation of DXA is its inability to differentiate high‑ versus low‑turnover renal osteodystrophy, which is important because anti‑resorptive agents may exacerbate low‑turnover bone disease. 8

Role of Bone Biopsy

• Bone biopsy is reasonable when the specific type of renal osteodystrophy would change management decisions. 8

• Indications include:

  • Inconsistent PTH trends that conflict with the clinical picture. 8
  • Unexplained hypercalcemia. 12
  • Persistent bone pain with rising bone‑specific alkaline phosphatase. 12
  • Uncertainty before initiating anti‑resorptive therapy. 8

• For CKD G3a‑G4, a bone biopsy is no longer required before starting anti‑resorptive therapy, given emerging evidence of efficacy and safety in these stages. 9

Management Framework – Optimizing Mineral Metabolism

• Serial assessment of phosphate, calcium, and PTH together (rather than isolated values) should guide treatment decisions. 8

• Lower elevated phosphate toward the normal range (Grade 2C evidence). Strategies include dietary phosphate restriction, non‑calcium‑based phosphate binders, and intensified dialysis for G5D patients. 8

• Avoid hypercalcemia in all CKD stages (Grade 2C evidence). 8

• Supplementation:

  • Provide vitamin D (≥ 400 IU daily) and monitor for hypercalcemia. Evidence from KDIGO and Kidney International supports this target. 10

Common Pitfalls to Avoid

• Do not order DXA if the result will not alter management; testing must be decision‑driven. 8

• Do not treat based on a single elevated PTH value; rely on longitudinal trends. 8

• Do not assume normal BMD excludes bone disease; CKD patients may have normal BMD yet abnormal bone turnover. 10