We conclude that urine volume is a real stone risk factor in nephrolithiasis and that a large intake of water is the initial therapy for prevention of stone recurrences. In cases of hypercalciuria it is suitable to prescribe adjuvant specific diets or drug therapy.

Expulsive medical therapy of ureteral stones is not well established. To test the efficacy of a calcium antagonist (nifedipine) associated with a corticosteroid (methylprednisolone) in facilitating ureteral stone passage, we studied 86 patients with a unilateral ureteral radiopaque stone not larger than 15 mm. in maximum diameter, confirmed in each case by drop excretory urography. Patients were randomly treated for a maximum of 45 days under double-blind conditions with 16 mg. methylprednisolone plus 40 mg. nifedipine daily (group 1-13 women and 30 men, mean age 45 +/- 14 years, standard deviation) and with 16 mg. methylprednisolone plus placebo daily (group 2-18 women and 25 men, mean age 43 +/- 14 years). All patients also received 2 l. of low mineral content water daily. The average maximum diameter of the stones was 6.7 +/- 3.0 mm. in group 1 and 6.8 +/- 2.9 mm. in group 2 (not significant). Partial ureteral obstruction was present in approximately half of the patients in both groups. Four patients in group 1 and 6 in group 2 dropped out of the study. In group 1, 34 patients had successful results (stone passage without surgical manipulation) and 5 failed (success rate 87%), compared to 24 and 13, respectively, in group 2 (success rate 65%). This difference was significant (p = 0.021, Fisher's exact test). No difference was present in the maximum stone diameter among the successful cases in groups 1 and 2 (6.4 +/- 2.8 and 5.3 +/- 2.2 mm., respectively, not significant). In both groups the maximum diameter of the stone was larger in the failed than in the successful cases (group 1-10.4 +/- 3.0 versus 6.4 +/- 2.8 mm., p = 0.005, and group 2-9.3 +/- 2.5 versus 5.3 +/- 2.2 mm., p = 0.0001). In group 1 the mean interval for stone passage in the successful cases was 11.2 +/- 7.5 days, compared to 16.4 +/- 11.0 days in group 2 (p = 0.036, Student's t test). We conclude that nifedipine associated with methylprednisolone is effective in facilitating ureteral stone passage.

We investigated the prevalence of stone disease and urinary stone risk factors in machinists chronically exposed to a hot environment and massive sweating, without interference of nephrotoxic metals or other lithogenic compounds. The study was performed at a glass plant and exposure to heat stress was estimated by the Wet Bulb Globe Temperature climatic index. The prevalence of nephrolithiasis on the entire population of the machinists was 8.5% (20 of 236), while the prevalence on the controls working in normal temperature was 2.4% (4 of 165) (p = 0.03). A high incidence (38.8%) of uric acid stones was present in the workers exposed to heat stress. Among the urinary stone risk indexes determined for 3 days during the 8-hour work shift on a randomly selected sample of 21 workers exposed and 21 workers not exposed to heat stress without any evidence of stone disease significant differences were found in uric acid concentration (722 +/- 195 versus 482 +/- 184 mg./l., p < 0.001), specific gravity (1,026 +/- 4 versus 1,021 +/- 6, p < 0.005) and pH (5.31 +/- 0.28 versus 5.64 +/- 0.54, p < 0.02), respectively. Thus, high uric acid relative supersaturation was present during occupation in hot temperatures (8.67 +/- 3.49) compared to occupation in normal temperatures (4.15 +/- 2.7) (p < 0.001). This study confirms that chronic dehydration represents a real lithogenic risk factor, mainly for uric acid stones, and adequate fluid intake is recommended during hot occupations.

An epidemiological study of stone disease in a Northern Italian city was carried out by means of a postal questionnaire mailed to 6000 individuals (2.5% of the entire population). It was found that the incidence of stone disease was comparable to that of industrialised Western Europe. There was a relationship between stone disease and gout and stone disease and a positive family history. The frequency of uric acid stones was high (26.5%). Stone-formers showed no alimentary differences from non-stone formers apart from the use of spices and herbs. Stone-formers used less water from public aqueducts and more uncarbonated mineral water, but only 19% of these drank at least 2 litres a day.

We conclude that urine volume is a real stone risk factor in nephrolithiasis and that a large intake of water is the initial therapy for prevention of stone recurrences. In cases of hypercalciuria it is suitable to prescribe adjuvant specific diets or drug therapy.