Diet plays an important role in kidney stone formation. Several individual components have been associated with the risk of kidney stone formation, but there is limited evidence regarding the role of healthful dietary patterns. To prospectively study the association between adherence to the Mediterranean diet and the risk of incident kidney stones. We conducted a longitudinal study using 3 different cohorts: the Health Professionals Follow-up Study (n = 42,902 men), the Nurses’ Health Study I (n = 59,994 women), and the Nurses’ Health Study II (n = 90,631 women). We assessed diet every 4 y using an FFQ and calculated adherence to a Mediterranean diet using the alternate Mediterranean diet score (aMED). A subgroup of 6077 participants provided ≥1 24-h urine sample, and urinary solute excretion was analyzed. We used Cox proportional hazards regression to examine the independent association between the aMED and incidence of kidney stones, adjusting for potential confounders. We used adjusted linear regression models to study the relation between aMED and urine composition. During 3,316,633 person-years of follow-up, 6576 cases of incident kidney stones were identified. For participants in the highest aMED score category, the risk of developing a kidney stone was between 13% and 41% lower compared with participants in the lowest score (pooled HR: 0.72, 95% CI: 0.59, 0.87; P value for trend <0.001). A higher aMED score was associated with higher urinary citrate, magnesium, oxalate, phosphate, uric acid, volume, and pH, and lower urinary sodium, resulting in lower supersaturation for calcium oxalate, calcium phosphate, and uric acid. Adherence to a Mediterranean diet is associated with a lower risk of developing a kidney stone.

The main aim of the current study was to evaluate the effectiveness of mixtures of magnesium, citrate and phytate as calcium oxalate crystallization inhibitors. A turbidimetric assay in synthetic urine was performed to obtain induction times for calcium oxalate crystallization in the absence and presence of different mixtures of inhibitors. The morphology of calcium oxalate crystals in the absence or presence of inhibitors and mixtures of the inhibitors was evaluated in 2 crystallization experiments at low and high calcium oxalate supersaturation. The crystals formed were examined using scanning electron microscopy. Examination of crystallization induction times revealed clear inhibitory effects of magnesium, citrate and phytate on calcium oxalate crystallization, supporting usefulness in the treatment and prevention of calcium oxalate nephrolithiasis. Significant synergistic effects between magnesium and phytate were observed. Scanning electron microscopy images revealed that phytate is a powerful crystal growth inhibitor of calcium oxalate, totally preventing the formation of trihydrate and monohydrate. In addition to crystallization inhibition capacity, citrate and magnesium avoided calcium oxalate crystallization by decreasing its supersaturation. The synergistic effect between magnesium and phytate on calcium oxalate crystallization suggests that a combination of these 2 compounds may be highly useful as antilithiasis therapy.

To assess the capacity of methylxanthines (caffeine, theophylline, theobromine and paraxanthine) to inhibit uric acid crystallization, and to evaluate their potential application in the treatment of uric acid nephrolithiasis. The ability of methylxathines to inhibit uric acid nucleation was assayed turbidimetrically. Crystal morphology and its modification due to the effect of theobromine were evaluated by scanning electron microscopy (SEM). The ability of theobromine to inhibit uric acid crystal growth on calculi fragments resulting from extracorporeal shock wave lithotripsy (ESWL) was evaluated using a flow system. The turbidimetric assay showed that among the studied methylxanthines, theobromine could markedly inhibit uric acid nucleation. SEM images showed that the presence of theobromine resulted in thinner uric acid crystals. Furthermore, in a flow system theobromine blocked the regrowth of post-ESWL uric acid calculi fragments. Theobromine, a natural dimethylxanthine present in high amounts in cocoa, acts as an inhibitor of nucleation and crystal growth of uric acid. Therefore, theobromine may be clinically useful in the treatment of uric acid nephrolithiasis.

Urinary pH is an important factor linked to renal stone disease and a useful marker in the treatment of urolithiasis. Although the gold standard for measuring urinary pH utilizes a glass electrode and a pH meter, at present dipstick testing is largely used to estimate urinary pH. However, the accuracy and precision of this method may be insufficient for making clinical decisions in patients with lithiasis. The aim of this study is to describe a new device for urinary pH testing. The device includes a pH sensor based on differential measurement of an ISFET-REFET pair. The drawbacks associated with this type of configuration, namely short lifetime and manual fabrication, have been overcome in the prototype. An automatic one point calibration is performed when turning on the system. Two buffer solutions were utilized to determine the intra- and inter-day precision of the device. The pH of 30 fresh human urine samples was measured using a pH-meter, a dipstick and the new electronic device. In some cases, dipstick measurements differed from those of the pH meter by more than 0.40 units, a clinically relevant discrepancy, whereas none of the measurements made with the new electronic device differed from the results of the pH-meter by more than 0.1 pH units. This new electronic device has the possibility to be used by stone-formers to control their urinary pH at home, increasing the tools available for stone prevention and prophylaxis.