Determinants of urolithiasis before and after parathyroidectomy in patients with primary hyperparathyroidism.

Objective: To assess the determinants of urolithiasis in patients with primary hyperparathyroidism (PHPT) before and after parathyroidectomy (PTX).

Methods: Institutional Research Ethics approval was obtained. A retrospective review was performed for patients presenting with PHPT to the stone, surgical oncology, and otolaryngology clinics at 2 tertiary-care centers from January 2006 to November 2011. Demographic, clinical, and surgical data were collected together with 24-hour urine collections before and after PTX.

Results: Of 332 patients undergoing PTX, 255 (68.2% female patients) had PHPT. Mean age was 60.3 years (range, 18-91). Before PTX, renal calcification was detected in 51 (20%) patients, nephrolithiasis in 48 (18.8%), and nephrocalcinosis in 3 (1.2%) patients. Compared with PHPT patients without stones, PHPT patients with stones were significantly younger (56.4 vs 61.3 years, P=.02), less likely to be female (54.9% vs 71.9%, P=.03), and had significantly lower levels of vitamin D (19.7 vs 23.5 ng/mL, P=.03). Nine patients (3.5%) developed stones after PTX and were found to have significantly higher post-PTX total serum calcium levels when compared with those without stones. Although hypercalciuria was detected in 62% of pre-PTX stone formers, none of those who tested had post-PTX hypercalciuria (P<.001). On multivariate regression analysis, post-PTX stone formation was associated with male gender (adjusted odds ratio [95% confidence interval]: 6.8 [5.3-7.2], P=.01) and post-PTX hypercalcemia (adjusted odds ratio [95% confidence interval]: 1.48 [1.33-2.12], P=.02).

Conclusion: Pre-PTX urolithiasis was associated with younger age, male gender, and lower levels of vitamin D, whereas post-PTX urolithiasis was independently predicted by male gender and hypercalcemia.