From the Guidelines
The next step in managing this 57-year-old postmenopausal woman with kidney stones who is taking calcium supplements for osteoporosis prevention is to assess urinary calcium excretion. This is based on the evidence from the study by EN Taylor and GC Curhan 1, which suggests that a patient with calcium urolithiasis who wishes to continue calcium supplementation should collect 24-h urine samples on and off the supplement to determine if the urinary supersaturation of the calcium salt in question increases during the period of supplement use. The following steps should also be considered:
- Increase fluid intake to at least 2-2.5 liters per day to help prevent stone formation 1
- Reduce sodium intake to less than 2,300 mg daily to decrease urinary calcium excretion 1
- Maintain normal dietary calcium intake (1,000-1,200 mg daily) to reduce the risk of stone formation 1
- Consider adding a thiazide diuretic like hydrochlorothiazide 12.5-25 mg daily if her 24-hour urine shows hypercalciuria to reduce urinary calcium excretion while protecting bone health 1 It is essential to note that calcium supplements remain important for her osteoporosis prevention, and appropriate calcium intake can actually reduce kidney stone risk when taken with meals by binding to oxalate in the gut 1. Some key points to consider:
- Calcium citrate is preferred over calcium carbonate for stone formers because it helps alkalize the urine and has better absorption 1
- The use of a urease inhibitor, AHA, may be beneficial in patients with struvite stones, although the extensive side effect profile may limit its use 1
- A 24-hour urine collection should be performed to identify specific metabolic abnormalities contributing to her stone formation 1
From the Research
Next Steps in Managing Kidney Stones
The patient in question is a 57-year-old postmenopausal woman with a history of kidney stones, currently taking calcium supplements for osteoporosis prevention. Given her condition, the next steps should focus on managing her kidney stone risk while considering her osteoporosis prevention needs.
- Assessing Urinary Calcium Excretion: This is a crucial step as it directly relates to her condition of forming kidney stones. High urinary calcium excretion can increase the risk of forming calcium stones 2, 3.
- Considering Thiazide Diuretics: Thiazide diuretics, such as hydrochlorothiazide, have been shown to reduce urinary calcium excretion and are used in the prevention of recurrent calcium kidney stones 3, 4, 5. However, their effectiveness and potential side effects, such as hypokalemia, should be carefully considered 4, 6.
- Monitoring Serum Calcium and Parathyroid Hormone: While assessing urinary calcium, it's also important to monitor serum calcium levels and parathyroid hormone (PTH) to understand the body's calcium regulation and to adjust treatments accordingly.
- Continuing or Adjusting Calcium Supplements: The decision to continue, adjust, or discontinue calcium supplements should be based on the patient's overall calcium balance, bone health, and risk of forming kidney stones. It's essential to weigh the benefits of calcium supplementation for osteoporosis prevention against the potential risk of increasing urinary calcium excretion.
- Other Considerations: Bone densitometry may be useful in assessing the patient's bone health and guiding the management of osteoporosis. However, this is more relevant to her osteoporosis prevention rather than the immediate management of kidney stones.
Key Considerations
- The use of thiazide diuretics can be effective in reducing urinary calcium excretion but may come with side effects and requires careful patient selection and monitoring 3, 4, 6.
- The management of kidney stones and osteoporosis prevention must be balanced, considering the potential interactions between treatments for these conditions.
- Regular monitoring of urinary and serum calcium, along with other relevant parameters, is essential for adjusting the treatment plan as needed.