As was mentioned in the previous section, increasing urinary levels of citrate decrease the chances of future stone formation. Citrate inhibits calcium oxalate and calcium phosphate stone formation by competing with oxalate and phosphate for the binding sites on the calcium ion, thereby limiting the total number of calcium oxalate and calcium phosphate crystals present in the urine. Citrate can also be metabolized in the body to bicarbonate, which causes the urine to become more alkaline (less acidic). This change in the urinary pH reduces the chances of uric acid from crystallizing into uric acid stones.
Patients with conditions such as renal tubular acidosis, Crohn's disease, and other similar forms of small intestine inflammatory diseases, and patients with chronic diarrhea often have problems with chronically low urinary citrate levels. In many patients who are found to have low urinary citrate levels, the true cause is usually not clear, however, increasing dietary citrate can have a significantly positive impact on their chances of preventing kidney stone disease.
Additionally, patients who are on diets that contain high levels of acid ash (sulfur-containing) food are at significant risk of forming both calcium and uric acid stones due to this diet's tendency to significantly lower urinary citrate levels.
Many patients with recurrent calcium containing stones have low urinary citrate levels despite enhancing the citrate level in their diet. Also, patients with recurrent uric acid stones are often unable to alkalinize their urinary pH to a level high enough to prevent recurrent uric acid stones. For these patients, citrate supplementation is an effective means of raising their urinary citrate levels as well as their urinary pH. (click table to enlarge)