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Kidney Stones

Update in Diagnosis and Management

Uric Acid is Very Insoluble at Low pH

Slide 23

February 2010

We will now briefly discuss other types of kidney stones. Fortunately, the urinary risk factors for each of these is more straightforward. Uric acid is very insoluble in urine with a pH less that 5.3. Hence, uric acid stones are all about having an acidic urine. Causes of acidic urine include excessive gastrointestinal losses of bicarbonate from diarrhea or illeostomies or a relatively protein rich diet such as the Atkins diet. More recently, it has been demonstrated that patients with insulin resistance or diabetes tend to have very acidic urine. The mechanism here seems to involve, at least in part, decreased renal ammoniagenesis and hence increased excretion of the daily acid load in the form of titratable acid. Treatment is fairly gratifying in that urinary alkalinization to a pH> 6 to 6.5 with oral citrate will effectively prevent uric acid crystallization, and even dissolve some pre existing uric acid stones.

Uric Acid Insoluble


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