A. A. Perez1, D. F. Schneider1, S. C. Pitt1, K. L. Long1, A. Chu1, R. S. Sippel1 1University Of Wisconsin,Endocrine Surgery,Madison, WI, USA
Introduction:
Kidney stones are a common manifestation of primary hyperparathyroidism (PHPT), and a strong indicator for surgical treatment of PHPT. Effective detection and treatment of PHPT is critical for managing the risk of recurrent stone disease and other complications of unmanaged PHPT. In this study, we examined predictors of kidney stones in PHPT patients and determined how effectively the diagnosis of PHPT is made in patients who first present with stones.
Methods:
We performed a retrospective analysis of surgically treated PHPT patients, comparing 247 patients who were kidney stone-formers (SF) and 1,047 patients with no stones (NS). We identified 51 SF patients who presented with a stone before their PHPT diagnosis, and whose stone evaluation and treatment was completed entirely within our health system for further analysis. Extracted data included clinical assessment and treatment of stones as well as timing of PHPT evaluation.
Results:
Compared to NS patients, SF patients were more likely to be male (28.6% vs 19.7%, p=0.002) and to be normocalcemic (26.6% vs. 16.9%, p=0.001) than the NS patients. SF patients also had higher alkaline phosphatase (92 IU/L vs. 85 IU/L, p=0.012) and higher 24-hour urinary calcium levels (342 mg/day vs 304 mg/day, p=0.005). On multivariate analysis, being male and having a higher 24-hour urine calcium and alkaline phosphatase were independently associated with a greater incidence of kidney stone formation. Despite these differences, 52.7% of SF had 24-hour urinary calcium levels within the normal range at the time of surgery. Of the 51 SF patients with full chart available for review, 72.5% (n=37) had a serum calcium drawn within 6 months of the first stone episode. Hypercalcemia was present in 43.2% of these patients (n=16), but only 10 (62.5%) of these patients had a serum PTH ordered within 3 months of their elevated calcium. Patients that had both a calcium and PTH drawn within 9 months of their first episode of kidney stones had a significantly shorter time from their first stone to surgical treatment than the other patients (median 8.5 months vs. 49.1 months, p=0.001).
Conclusion:
SF patients were found to be stronger excreters of calcium, but elevated urinary calcium and serum alkaline phosphatase levels did not identify the majority of PHPT patients at risk of forming kidney stones. Many patients with kidney stones had normal serum calcium levels and normal urinary calcium levels highlighting the need to carefully evaluate all SF for the possible treatable cause of hyperparathyroidism. Timely consideration of PHPT as well as prompt serum calcium and PTH evaluation significantly reduces time to treatment and minimize the risks of complications of longstanding PHPT.
