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Kidney Stones

Update in Diagnosis and Management

Calcium Phosphate is Very Insoluble at High pH!

Slide 24

February 2010

Calcium phosphate stones are the exact opposite, since calcium phosphate precipitates in urine with an alkaline pH > 6.3. Many of these patients have a defect in renal acidification, or renal tubular acidosis.

Causes include autoimmune diseases affecting the kidney such as Sjogrens disease, monoclonal protein diseases with peritubular deposits, and certain drugs (for example toperimate or acetazolamide which both block carbonic anhydrase).

In patients with renal tubular acidosis, in addition to a high urinary pH, they also develop hypocitraturia because of the associated systemic acidosis, as well as hypercalciuria, probably due to effects of bone buffering of the acid load. All of these also favor calcium phosphate precipitation.

Treatment often consists of citrate repletion with potassium citrate, although this can potentially make things worse if the urinary pH goes up further. Therefore, it is very important to watch serial urinary supersaturation profiles to monitor treatment effect in these patients.

Calcium Phosphate Insoluble


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