Hydrochlorothiazide for Kidney Stone Recurrence Prevention

Nephrolithiasis is a global healthcare problem with a current lifetime risk of 18.8% in men and 9.4% in women. Without specific treatment, 5- and 20-year recurrence rates are 40% and 75%, respectively. Given the high cost of medical treatments and surgical interventions as well as the morbidity related to symptomatic stone disease, medical prophylaxis for stone recurrence is an attractive approach. About 80-90% of stones are composed of calcium oxalate with various admixtures of calcium phosphate. Increased excretion of calcium in the urine, hypercalciuria, is the most common metabolic abnormality encountered in patients with recurrent nephrolithiasis. Thiazide diuretics have been the cornerstone of pharmacologic metaphylaxis for more than 40 years. The effect of thiazides to reduce the risk of stone recurrence has been attributed to their ability to decrease urinary calcium excretion. However, other factors, such as reduction of urinary pH and urinary oxalate excretion, probably contribute to this effect. Efficacy of thiazides on recurrence prevention of calcareous nephrolithiasis was tested in 11 randomized controlled trials (RCTs). With the exception of two trials, thiazides significantly reduced stone recurrence. Most of these trials are from the 1980's and 90's and the cumulative number of patients studied is remarkably low for such a prevalent disease. Our systematic review of these RCTs revealed major methodological deficiencies in all trials, including: lack of double-blinding and intention-to-treat analysis, unclear allocation concealment, lack of adverse event and drop out reporting and unknown baseline risk of disease severity. Furthermore, high doses of thiazides were employed in all trials, in the case of the best studied thiazide, hydrochlorothiazide (HCTZ), up to 100 mg daily. At such high doses, side effects occur frequently. Nowadays, thiazides are widely used in the treatment of recurrent nephrolithiasis and arterial hypertension, but at significantly lower doses. In the case of recurrent nephrolithiasis, however, this practice is not supported by randomized evidence and consequently, the investigators do not know whether the currently employed low dose thiazide regimens are effective in reducing the risk for stone recurrence. Thus, evidence for benefits and harms of thiazide diuretics in the prevention of calcium-containing kidney stones in general remains unclear. In addition, the efficacy of the currently employed low dose thiazide regimens to prevent stone recurrence is not known.