Renal stones and calcifications in patients with primary hyperparathyroidism: associations with biochemical variables

Objective: To study the prevalence of renal stones and nephrocalcinosis in patients with primary hyperparathyroidism (PHPT) and to appraise biochemical variables as risk factors for developing renal calcifications. Design: Cross-sectional. Materials and methods: All patients (n=177) undergoing diagnostic evaluation and surgery for PHPT at Aarhus University Hospital between 2007 and 2009. All patients underwent routine spiral CT scans of the abdomen to determine the presence or absence of renal calcifications. Results: A total of 45 patients (25.4%, 95% confidence intervals: 19.0-31.4%) had renal stones (15.3%) and/or renal calcifications (10.2%) on the CT scans. Compared with those without calcification (n=132), the group with calcification had a significantly lower plasma creatinine level (67.0+25.1 vs 74.6+17.5 mu mol/l, 2P=0.03). Moreover, CaE was higher in PHPT patients with renal calcification than in PHPT patients without (0.91 +/- 0.28 vs 0.74 +/- 0.40 mmol/mmol, 2P=0.02). The other measured or derived biochemical variables were similar in the two groups. No biochemical variable was predictive for renal calcifications in a multiple regression analysis. Conclusion: We found a high prevalence of renal calcifications among PHPT patients but no deterioration of renal function. The occurrence of calcifications was related to low plasma creatinine and a high urine calcium/creatinine ratio. However, biochemical markers in general were poor predictors for the risk of renal stones or nephrocalcinosis indicating that routine image diagnostics may be needed for the identification of these complications in order to establish indication for surgery and ensure proper treatment.