Hyperphosphatemia due to impaired phosphate excretion occurs in which condition?

• A. Renal failure
• B. Massive cellular lysis releasing phosphate
• C. Increased calcium citrate complexation
• D. Crush injury

Answer: (A)

Phosphate balance is largely controlled by the kidneys, which filter phosphate and then excrete what isn’t needed. When kidney function is impaired, phosphate excretion drops, so serum phosphate rises—that’s hyperphosphatemia due to impaired excretion, as seen in renal failure. The other scenarios raise phosphate for different reasons: massive cellular lysis or crush injury release phosphate from damaged cells into the blood, not because excretion is faulty; increased calcium citrate complexation mainly affects calcium binding rather than causing persistent phosphate retention.