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Abstract: SA-PO304

Differential Effects of Thiazide, Alkali, or Both on Urine Determinants of Stone Risk in Calcium Oxalate (CaOx) and Calcium Phosphate (CaP) Stone Formers

Session Information

Category: Bone and Mineral Metabolism

  • 502 Bone and Mineral Metabolism: Clinical

Authors

  • Steely, Audrey, University of Chicago Division of the Biological Sciences, Chicago, Illinois, United States
  • Worcester, Elaine M., University of Chicago Division of the Biological Sciences, Chicago, Illinois, United States
  • Prochaska, Megan, University of Chicago Division of the Biological Sciences, Chicago, Illinois, United States
Background

Thiazide type diuretics, potassium citrate (K-Cit), and lifestyle changes are used to prevent calcium kidney stones. Thiazides decrease stone risk by decreasing urine calcium (Ca). Citrate (Cit) is an inhibitor that decreases urine supersaturations (SS); however, it also increases urine pH and therefore Ca phosphate (CaP) SS. Thus, the effect of K-Cit on stone risk is complex.

Methods

To study the effects of common treatments for Ca stone risk we analyzed the 24-hour urinalysis of Calcium Oxalate (CaOx) and CaP stone formers (SF) by 4 different treatment types: lifestyle, K-Cit, thiazide, or both medications.

Results

Thiazides reduced urine Ca in both CaOx SF (-74±95 mg/day) and CaP SF (-102±100 mg/day). K-Cit alone and when combined with thiazide had no effect on urine Ca. K-Cit increased urine Cit in CaOx SF (252±306 mg/day), but not in CaP SF (36±353 mg/day). Thiazide decreased urine Cit among CaP SF (-118± 249 mg/day). K-Cit and thiazide combined increased Cit in CaOx SF (118±264 mg/day), but not CaP SF (94±217 mg/day). Urine pH rose in all groups except CaP SF on only lifestyle treatment. Among CaOx SF, pH increased in patients receiving K-Cit (0.6±0.6) and both (0.7±0.6) compared to patients receiving thiazide (0.1±0.5). There is a similar pattern among CaP SF receiving K-Cit (0.3±0.5), both (0.5±0.5), or thiazide (0.1±0.3). Thiazide decreased CaOx SS in both CaOx SF (-3.3±3.5) and CaP SF (-3.1±2.9). K-Cit did not lower CaOx SS in either CaOx or CaP SF. Thiazide decreased CaP SS in both CaOx SF (-0.5±0.9) and CaP SF (-0.8±0.9).

Conclusion

K-Cit had no significant effect on urine Ca and increased urine Cit levels in CaOx SF; however, increased urine pH lead to increased CaP SS for CaOx SF. The study raises questions about the best preventive treatment for patients with CaP stones and suggests that K-Cit may not confer the same benefits on CaP SF as it does on CaOx SF.

Figure 1. Boxplots of the change in urine CaOx and CaP SS by treatment group and stone type. Each includes t-tests comparing treatment groups.

Funding

  • NIDDK Support