How should I evaluate and manage bone mineral density in an adult with chronic kidney disease (stage 3–5, eGFR <60 mL/min/1.73 m²) who is at risk for osteoporosis?

Evaluation and Management of Bone Mineral Density in CKD

In adults with CKD stages 3–5 (eGFR <60 mL/min/1.73 m²) at risk for osteoporosis, perform DXA BMD testing to assess fracture risk if the results will change your treatment decisions, as hip BMD reliably predicts fractures across all CKD stages. 1

When to Perform BMD Testing

Obtain DXA BMD in CKD G3a-G5D patients who have:

• Evidence of CKD-MBD (elevated PTH, abnormal calcium/phosphate) 1
• Traditional osteoporosis risk factors (postmenopausal women, men >50 years, glucocorticoid use) 1
• Only if low or declining BMD will lead to interventions such as fall prevention strategies or osteoporosis medications 1

The 2017 KDIGO guideline reversed the 2009 recommendation against routine BMD testing after prospective cohort studies demonstrated that hip BMD predicts fractures in CKD patients with accuracy similar to the general population. 1

Initial Biochemical Assessment

Before ordering DXA, measure these parameters to evaluate for CKD-MBD:

• Serum calcium 1, 2
• Serum phosphate 1, 2
• Intact PTH 1, 2
• Alkaline phosphatase activity 2, 3
• 25-hydroxyvitamin D 1, 2

Monitoring frequency based on CKD stage: 2

• CKD G3a-G3b: Every 6-12 months
• CKD G4: Every 3-6 months
• CKD G5/G5D: Every 1-3 months

Base treatment decisions on trends in PTH levels, not single values. 1

Interpreting DXA Results in CKD

Hip BMD is the most reliable site for fracture prediction in CKD. 1 Multiple studies show consistent associations between low hip BMD and fracture risk across CKD stages G3a-G5D. 1

Use WHO T-scores as in the general population – they predict fracture risk similarly in CKD patients, including dialysis and transplant recipients. 1

Important limitation: DXA cannot distinguish between types of renal osteodystrophy (high vs. low bone turnover). 1 This matters because antiresorptive agents may worsen low-turnover bone disease. 2

When to Consider Bone Biopsy

Bone biopsy is reasonable when knowing the type of renal osteodystrophy will change management: 1

• PTH trends are inconsistent or conflicting with clinical picture 1
• Unexplained hypercalcemia develops 1, 3
• Persistent bone pain with rising bone-specific alkaline phosphatase 1, 3
• Before starting antiresorptive therapy in uncertain cases 1

Critical update: Bone biopsy is no longer a prerequisite before antiresorptive therapy in CKD G3a-G4, given growing evidence of efficacy and safety in these stages. 1

Management Framework

Optimize Mineral Metabolism First

Treat based on serial assessments of phosphate, calcium, and PTH together, not isolated values: 1, 2

1. Lower elevated phosphate toward normal range (Grade 2C) 1, 2

   • Dietary phosphate restriction
   • Phosphate binders (limit calcium-based binders) 2
   • Intensified dialysis for G5D patients 2

2. Avoid hypercalcemia in all CKD stages (Grade 2C) 1, 2

3. Treat progressively rising or persistently elevated PTH 2

   • Non-dialysis: Avoid routine calcitriol/vitamin D analogues (hypercalcemia risk) 2
   • Dialysis: Calcimimetics, calcitriol, or vitamin D analogues acceptable 2

4. Ensure adequate supplementation: 1

   • Calcium 1000 mg daily
   • Vitamin D at least 400 IU daily (monitor for hypercalcemia) 1, 2

5. Treat metabolic acidosis to reduce bone resorption 4, 2

Antiresorptive Therapy Considerations

For CKD G3a-G4 with low BMD and traditional osteoporosis risk factors:

• Bisphosphonates (alendronate, risedronate) and denosumab have comparable efficacy in improving BMD and reducing fractures 5
• No longer contraindicated based on eGFR alone in stages 3-4 5

Critical warnings for advanced CKD (G4-G5D): 6

Denosumab carries a boxed warning for severe hypocalcemia in advanced kidney disease. 6 Before initiating:

• Evaluate for CKD-MBD with intact PTH, serum calcium, 25(OH)D, and 1,25(OH)₂D 6
• Treatment should be supervised by a provider with CKD-MBD expertise 6
• The presence of CKD-MBD markedly increases hypocalcemia risk 6

Monitor serum calcium closely after any antiresorptive agent, especially in CKD G4-G5D. 6

Common Pitfalls to Avoid

1. Don't order DXA if results won't change management – testing should be decision-driven 1

2. Don't rely on spine BMD alone – hip BMD is more reliable in CKD, as spine measurements can be falsely elevated by vascular calcification 7

3. Don't treat based on a single elevated PTH value – use trends over time 1, 2

4. Don't assume normal BMD excludes bone disease – CKD patients can have normal BMD with abnormal bone turnover 1

5. Don't start antiresorptives without correcting hypocalcemia first – pre-existing hypocalcemia must be corrected 6

6. Don't use bone-specific alkaline phosphatase alone – it's more reliable than PTH for bone turnover assessment but should be combined with other markers 3, 8

Ongoing Monitoring

Continue monitoring in patients receiving treatment: 2

• Serial BMD measurements to assess response 2
• Regular biochemical monitoring of calcium, phosphate, PTH 2
• Assess for complications: osteonecrosis of jaw, atypical femoral fractures 6

If discontinuing denosumab, transition to another antiresorptive agent to prevent multiple vertebral fractures. 6