Dissolution of radiolucent renal stones by oral alkalinization with potassium citrate/potassium bicarbonate.

AIM: Uric acid stone disease is dependent on three pathogenetic factors: acid urine pH, low urine volume, and hyperuricosuria. However, the most important factor for uric acid stone formation is persistently acidic urine that represents a prerequisite for uric acid stone formation and growth. Urinary alkalization with alkali administration has been advocated for dissolution of stones on the basis of estabilished clinical experience. The aim of this study was to evaluate the clinical efficacy of therapy with potassium citrate/potassium bicarbonate for dissolution of radiolucent stones.

PATIENTS AND METHODS: A total of 8 patients with radiolucent stones (< or = 15 mm) in functioning kidneys were enrolled (4 M, 4 F; mean age 66 +/- 2 years) Ultrasonography (or computed tomography scan) was done to confirm stone presence and burden and plain X-ray to exclude calcified stones. At basal a blood sample was drawn for glucose, creatinine and uric acid measurement and a 24 hour urine sample was collected for evaluation of daily uric acid excretion. Urine cultures were also performed in order rule out urinary tract infection. All patients at presentation and weekly during the study period filled out urinary pH and volume diaries. Each study day three samples of urine were collected for pH and volume measurement (morning from 8 AM to 2 PM; afternoon from 2 PM to 8 PM, and night from 8 PM to 8 AM). Two study periods were considered: during the first 6 week period a daily water intake of 1500 ml was suggested whereas in the following 6 week period the same water intake plus potassium citrate 40 mEq and potassium bicarbonate 20 mEq (divided in two doses). Potassium alkali were chosen in order to reduce the risk of calcium precipitation because of their calcium-lowering effect. The effects of treatment on stone dissolution was evaluated by ultrasonography after each study period (6 weeks and 12 weeks).

RESULTS: During the first period of treatment stone burden remained unchanged in all patients. On the contrary after 6 weeks of potassium citrate/bicarbonate treatment, complete stone dissolution was found in three of the patients. In the other five cases a partial dissolution was observed and in two of them complete dissolution of the stone was achieved after prolongation of the treatment for 4 and 6 month respectively. Mean urinary volumes were unchanged during all the two study periods. Mean urinary pH was significantly higher during the potassium citrate/bicarbonate treatment period in comparison to the first study period (morning 6.60 +/- 1.06 vs 5.53 +/- 0.51, p = 0.030; afternoon 6.53 +/- 0.70 vs 5.63 +/- 0.41, p = 0.007; night 6.57 +/- 0.51 vs 5.98 +/- 0.80, p = 0.092). Tolerance of the drug was good, and no serious effects were observed sufficient to interrupt treatment. None of the patients required subsequent interventions for stone treatment.

CONCLUSION: Urinary alkalization with potassium citrate/bicarbonate is a well tolerated and highly effective treatment, resulting in dissolution of nonobstructing uric acid stones.