Makindo Medical Notes

⚠️ Hyperphosphataemia is common in patients with kidney disease and can lead to vascular and soft tissue calcification if not recognised and treated early.

📖 About

• Hyperphosphataemia = elevated phosphate in the blood.
• Common in chronic kidney disease (CKD) and acute kidney injury (AKI).

📊 Aetiology / Definition

• Serum phosphate >4.5 mg/dL (>1.46 mmol/L).
• 🩺 Reduced GFR → decreased phosphate excretion.
• ⬇️ PTH or pseudo-hypoparathyroidism → increased tubular phosphate reabsorption.

🔎 Causes

• ⛔ CKD stages 3–5 or AKI (most common).
• 💊 Phosphate-containing enemas or laxatives.
• 🧬 Tumour lysis syndrome or rhabdomyolysis (massive cell breakdown).
• 🦴 Endocrine: Hypoparathyroidism & pseudohypoparathyroidism.

🧑‍⚕️ Clinical Features

• Often asymptomatic (detected biochemically).
• 🩻 Can cause metastatic calcification in vessels/soft tissue.
• 📈 Chronic phosphate retention → secondary hyperparathyroidism.
• Severe cases: tetany, pruritus, red eyes (calcific conjunctivitis).

🔬 Investigations

• Check U&E, creatinine, phosphate (P), calcium (Ca), magnesium (Mg), potassium (K).
• 🔄 Look at calcium–phosphate product (risk of calcification if >55 mg²/dL²).
• 📈 PTH: Elevated in secondary hyperparathyroidism due to CKD.

💊 Management

• 👩‍⚕️ Treat underlying renal disease.
• 🥗 Dietary phosphate restriction (avoid cola drinks, dairy, processed foods).
• 💊 Phosphate binders (e.g., Sevelamer, Lanthanum, Calcium acetate).
• 💧 IV fluids: improve GFR & phosphate excretion (useful in AKI/TLS).
• 🧬 Tumour lysis syndrome: IV saline, allopurinol/rasburicase, dialysis if refractory.
• Dialysis in severe symptomatic hyperphosphataemia with renal failure.

💡 Pearls

• Always interpret phosphate in context of calcium — high phosphate + low calcium → neuromuscular irritability.
• Long-term complication: vascular calcification → accelerated atherosclerosis in CKD patients.
• Phosphate binders are taken with meals to block absorption.
• Dialysis patients: serum phosphate control is crucial to reduce cardiovascular risk.

📚 References

• BNF – Sevelamer
• National Kidney Foundation – Phosphorus and Kidney Disease