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E-Case #4-B Davonna Cufley, M.D. July 2-6, 2001 Ms. U is a 76 yo woman who comes in for routine follow-up. History includes manic-depressive disorder, nephrolithiasis x 2, GERD, and osteoporosis. Bone scan 1 yr ago showed T-score of 3.18 at the hip. She was prescribed alendronate but stopped it due to "aching in all my bones." She refuses estrogen as it caused mood changes. She wants to prevent hip fracture and has begun calcium supplementation, but is concerned that it may be increasing her risk for recurrent nephrolithiasis. A 24-hour urine for calcium excretion was normal 1 year ago. What is the risk of causing recurrent nephrolithiasis from calcium supplementation? Or from dietary calcium? Curhan, et al: Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Annals of Internal Medicine, Volume 126(7). 1 April 1997 497-504 Design: prospective cohort study over 12 years; 91,731 women from the Nurses Health Study who had no history of kidney stones. Self-administered food frequency questionnaires were used to assess diet. The main outcome measure was incident symptomatic kidney stones. Lower stone formation was seen with higher dietary calcium: RR .65 for women in the highest quintile of dietary calcium intake compared with women in the lowest quintile (CI .50 to .83). The relative risk in women who took supplemental calcium compared with women who did not was 1.2 (CI 1.02 to 1.41). Conclusions: high intake of dietary calcium appears to decrease risk for symptomatic kidney stones, whereas intake of supplemental calcium may increase risk. Because calcium reduces the absorption of oxalate, the apparently opposite effects of supplemental vs dietary calcium may be associated with the timing of calcium ingestion relative to the amount of oxalate consumed. However, other factors present in dairy products (the major source of dietary calcium) could be responsible for the decreased risk seen with dietary calcium. Note: a diet high in sodium increased risk (1.3), as did sucrose (1.52), but fluid (.61) and potassium (.65) lowered risk. Is osteoporosis more common in pts with nephrolithiasis? Yes. Lower bone mineral density is seen in renal calcium stone formers, especially in hypercalciuric patients (Trinchieri, et al., 1998). Stone formers without hypercalcuria, like Mrs. U, may have low bone density, too: 44% (15 of 34) of normocalciuric patients in Trinchieri's series of male stone formers had low bone density. Diet is important: in this series, dietary calcium intake and serum calcium was significantly lower in those with low bone mineral density compared to those with normal bone density. Trinchieri: J Urol, Volume 159(3). March 1998 654-7 References have been sent to each clinic site.
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