Which of the following is a major renal manifestation of hypercalcemia?

• A. Hematuria
• B. Proteinuria
• C. Kidney stones
• D. Flank pain

Answer: (C)

When calcium is high, the kidneys handle more calcium by excreting it in the urine, making the urine supersaturated with calcium salts. This favors precipitation and stone formation, especially calcium oxalate stones, so calcium-based kidney stones are the major renal manifestation of hypercalcemia. Hematuria or proteinuria can occur but are not the defining renal feature, and flank pain is typically a symptom that arises with passing a stone rather than a direct result of hypercalcemia itself. Chronic hypercalcemia can also impair the kidney’s concentrating ability and lead to nephrocalcinosis or diabetes insipidus, but the classic renal issue doctors look for with elevated calcium is calcium stone formation.