Stones left unturned: Missed opportunities to diagnose primary hyperparathyroidism in patients with nephrolithiasis.

Background: Nephrolithiasis is a sequela of primary hyperparathyroidism and an indication for parathyroidectomy. The prevalence of primary hyperparathyroidism in patients with nephrolithiasis is 3% to 5%; however, recent studies suggest that many hypercalcemic patients with nephrolithiasis never undergo workup for primary hyperparathyroidism. Our goal is to evaluate primary hyperparathyroidism screening rates at a tertiary academic health institution and identify opportunities to increase referral rates in patients presenting with nephrolithiasis.

Methods: We retrospectively reviewed 15,725 patients across an academic health system who presented with nephrolithiasis between 2012 and 2020. Calcium levels measured within 6 months of presentation were identified, and those with hypercalcemia (≥10.3 mg/dL) were reviewed if parathyroid hormone levels were measured. Patients with primary hyperparathyroidism were evaluated to see if they were referred to a specialist for treatment.

Results: Of 15,725 patients presenting with nephrolithiasis, 12,420 (79%) had calcium levels measured; 630 patients (4.0%) were hypercalcemic, and 207 (33%) had parathyroid hormone levels measured. Patients were more likely to have parathyroid hormone levels sent if they were older, had higher calcium levels, or presented to an outpatient clinic (P = .028, P = .002, P < .001). We identified 89 patients (0.6%) with primary hyperparathyroidism, of which only 35 (39%) were referred for treatment.

Conclusion: The proportion of patients presenting with nephrolithiasis ultimately diagnosed with primary hyperparathyroidism was significantly lower than others have reported. Additionally, a substantial number of patients with nephrolithiasis did not have calcium and/or parathyroid hormone levels measured. These missed opportunities for diagnosis are critical as early definitive management of primary hyperparathyroidism can prevent recurrent nephrolithiasis and other primary hyperparathyroidism-related end organ effects.