How to manage hyperphosphatemia?

Management of Hyperphosphatemia in Chronic Kidney Disease

For patients with CKD G3a-G5D, treatment of hyperphosphatemia should be initiated only for progressively or persistently elevated serum phosphate levels, focusing on dietary phosphate restriction, phosphate binders, and increased dialytic removal in dialysis patients. 1

Diagnostic Approach

• Monitor serum phosphate levels based on CKD stage:
  • CKD G3a-G3b: Every 6-12 months
  • CKD G4: Every 3-6 months
  • CKD G5/G5D: Every 1-3 months 1

Treatment Algorithm

Step 1: Dietary Phosphate Management

• Limit dietary phosphate intake to treat hyperphosphatemia 1
• Consider phosphate source when making dietary recommendations:
  • Animal-based phosphate: 40-60% absorption
  • Plant-based phosphate: 20-50% absorption
  • Inorganic phosphate (food additives): Highest bioavailability 1
• Practical recommendations:
  • Guide patients toward fresh and homemade foods rather than processed foods
  • Educate patients about hidden phosphate sources in food additives
  • Involve an experienced dietitian in phosphorus management 1

Step 2: Phosphate Binders

• Initiate phosphate binders only for progressively or persistently elevated serum phosphate 1
• Phosphate binder selection:
  1. Avoid aluminum-containing phosphate binders for long-term use due to toxicity risk 1
  2. Restrict dose of calcium-based phosphate binders in adults with CKD G3a-G5D 1
  3. Consider non-calcium based binders (sevelamer, lanthanum carbonate, iron-based binders) when:
     • Risk of hypercalcemia exists
     • Evidence of vascular calcification is present
     • PTH levels are persistently low 1

Step 3: For Dialysis Patients (CKD G5D)

• Increase dialytic phosphate removal for persistent hyperphosphatemia 1
• Use dialysate calcium concentration between 1.25-1.50 mmol/L (2.5-3.0 mEq/L) 1

Management of Associated Conditions

Secondary Hyperparathyroidism

• Evaluate patients with progressively rising or persistently elevated PTH for:
  • Hyperphosphatemia
  • Hypocalcemia
  • High phosphate intake
  • Vitamin D deficiency 1
• Treatment approach:
  • Increase active vitamin D dosage and/or decrease phosphate supplement dosage 2
  • For severe hyperparathyroidism (PTH >800 pg/mL) refractory to medical therapy, consider parathyroidectomy 2

Calcium Management

• In adults with CKD G3a-G5D, avoid hypercalcemia 1
• In children with CKD G3a-G5D, maintain serum calcium in age-appropriate normal range 1

Target Levels and Monitoring

• Aim for serum phosphate levels toward the normal range 1
• Target calcium-phosphorus product <55 mg²/dL² 3
• For PTH, target 100-200 pg/mL for dialysis patients 3
• Monitor treatment response regularly:
  • Serum phosphate, calcium, and PTH levels
  • Signs of adverse effects (hypercalcemia, gastrointestinal symptoms)
  • Vascular calcification

Important Considerations and Pitfalls

1. Avoid preventive treatment: Do not initiate phosphate-lowering therapy in normophosphatemic patients with CKD 1

2. Balance risks of calcium-based binders: While effective, they may contribute to vascular calcification. The 2017 KDIGO update moved away from recommending calcium restriction only in specific conditions to a more general recommendation to restrict calcium-based binder doses 1

3. Consider food sources: Not all dietary phosphate is equally bioavailable. Focus on reducing highly absorbable inorganic phosphate from food additives 1

4. Individualize phosphate binder selection: Consider CKD stage, presence of other CKD-MBD components, and side effect profiles 1

5. Recognize limitations of dietary restriction alone: In most CKD patients, dietary restriction while maintaining adequate protein intake is not sufficient to control serum phosphate levels 4

By following this evidence-based approach to hyperphosphatemia management, clinicians can help reduce cardiovascular morbidity and mortality associated with phosphate abnormalities in CKD patients.