Idiopathic Hypercalciuria Diagnosis — ESENeph MCQ

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EasyRenal Stone DiseaseIdiopathic Hypercalciuria DiagnosisESENeph

A 50-year-old man with CKD G3a has a 24-hour urine calcium of 12 mmol/day (elevated). His serum calcium is 2.35 mmol/L (normal) and PTH is 4.2 pmol/L (normal). He has had 3 calcium oxalate stones. What is the diagnosis?

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Correct answer: D — Idiopathic hypercalciuria

Elevated urinary calcium with normal serum calcium and normal PTH defines idiopathic hypercalciuria – the most common metabolic abnormality in calcium stone formers (found in 40-60%). It may be absorptive (increased GI calcium absorption), renal (reduced tubular reabsorption), or resorptive. Treatment includes Thiazide diuretics (reduce urinary calcium), dietary sodium restriction (<2 g/day – sodium and calcium share proximal tubular reabsorption), adequate dietary calcium (1000-1200 mg/day – low calcium diets paradoxically worsen stones), and high fluid intake.

Reference: EAU 2024 – Urolithiasis; Coe et al 2005 – Idiopathic Hypercalciuria