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

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

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.

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).

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.