Drinking water composition and incidence of urinary calculus: introducing a new index

We searched for a pathophysiologically based feature of major water electrolytes, which may define water quality better than the water hardness, respecting urinary calculus formation. Utilizing a multistage stratified sampling, 2310 patients were diagnosed in the imaging centers of the provincial capitals in Iran between 2007 and 2008. These were composed of 1755 patients who were settled residents of 24 provincial capitals. Data on the regional drinking water composition, obtained from an accredited registry, and their relationships with the region's incidence of urinary calculi were evaluated by metaregression models. The stone risk index [defined as the ratio of calcium to magnesium-bicarbonate product in drinking water] was used to assess the risk of calculus formation. No correlation was found between the urinary calculus incidence and the amount of calcium, bicarbonate, or the total hardness of the drinking water. In contrast, water magnesium had a marginally significant nonlinear inverse relationship with the incidence of the disease in the capitals [R2 = 26%, P = .05 for a power model]. The stone risk index was associated nonlinearly with the calculus incidence [R2 = 28.4%, P = .04]. Urinary calculus incidence was inversely related with drinking water magnesium content. We introduced a new index constructed on the foundation of a pathophysiologically based formula; the stone risk index had a strong positive association with calculus incidence. This index can have therapeutic and preventive applications, yet to be confirmed by clinical trials

Familial relations and recurrence pattern in nephrolithiasis. New words about old subjects

While medical and surgical approaches to urolithiasis are different for single and recurrent stone former [RSF], the RSF definition itself is commonly overlooked. Moreover, despite consensus on association between family history [FH] and urolithiasis, more epidemiologic evidence is required to clarify the nature of this relationship. Our purpose was to propose a more precise definition of RSF, and also to investigate how family history may affect urolithiasis. Using a multistage stratified sampling in 4 seasonal phases, 6127 subjects with imaging-proven urolithiasis were detected in 12 Iranian regions. The FH of urolithiasis and the average interval between episodes [cycles] were determined by an informed interview. Of 6127 patients with the mean age of 41.8 +/- 15.1 years, 42% had FH, and 22.2% were RSF of whom 61% were men. The patients with FH had a greater chance of recurrence [OR = 1.2, 95% Confidence Interval [CI], 1.1 to 1.4]. Furthermore, patients with positive FH had more episodes [P = .0001], comparable cycles and younger ages at the onset [P = .02] than those patients without a FH. In the RSF group, the 90[th] percentiles of the cycle were 60 months and the estimated mean stone cycle for the population was 25.34 months [99% CI, 23.0 to 27.7]. Family history seems very common in Iranian population and is a risk factor for recurrence. Moreover, RSF could be identified by the estimated average cycle in the population [25.3 months] or by the percentiles