Hypophosphatemia

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Presentation :

• Characteristic findings in severe hypophosphatemia are HF, muscle weakness, rhabdomyolysis, hemolytic anemia, and metabolic encephalopathy

Pathophysiology :

• Common causes include:
  • refeeding after starvation
  • insulin administration for severe hyperglycemia
  • hungry bone syndrome following parathyroidectomy
  • respiratory alkalosis
  • chronic diarrhea
  • chronic alcoholism
  • hyperparathyroidism
  • vitamin D deficiency

Diagnostic Testing:

• If the cause of hypophosphatemia is not evident from the history, a 24-hour urine phosphate collection or calculation of the FePO4 from a random urine sample can help differentiate renal from extrarenal causes:
  • FePO4 = (Urine PO4 × Serum Creatinine × 100)/(Serum PO4 × Urine Creatinine)
• Urine phosphate excretion >100 mg/d or an FePO4 >5% indicates renal phosphate wasting

Treatment :

• In asymptomatic patients, administer oral phosphorus replacement as a sodium or potassium salt (ie: PhosNaK).
• IV phosphate repletion is indicated for symptomatic patients or for those whose phosphorus level is <2 mg/dL.

Prognosis:

References: