**7. Impact of fluid on urolithiasis**

Less fluid intake is one of the major risk factors in the stone formation, whereas adequate amount of urine excretion will eventually reduce the saturation of urine. To achieve 2 L/day of urine excretion fluid intake should be higher at the range of 2–3 L/day as water will be lost for extra renal functions like sweating, breathing and perspiration [45]. Along with volume of fluid intake, the quality and composition of fluid or water is also equally responsible for stone formation and it can be considered as a modifiable risk factor. Many studies have reported that high amount of fluid intake will eventually reduce the risk of urolithiasis [46].

Apart from water, other beverages like soda, tea, coffee and aerated or carbonated drinks consumption will also be having their impact on stone formation. High intake of sugar sweetened soda rich with fructose increases the risk of urolithiasis, as fructose promotes synthesis of uric acid and increases the excretion of uric acid, calcium and oxalate in urine [47]. Fructose rich food, makes the cells to utilise excess ATP for its uptake and such monosaccharides reduces phosphate concentrations within the cells and induces production of uric acid which leads to hyperuricosuria. So, in hyperuricosuria patients, it's advisable to reduce the intake of fruits, beverages and fruit juices rich with fructose content [48]. Another study conducted by Shuster et, al. reported that intake of carbonated/aerated beverages is also one of the risk factors for formation of calculi as these beverages contains high amount of phosphoric acid [49]. On the contrary some studies also evidenced that citric soda content of the aerated drinks has a capacity to reduce the risk of stone formation by increasing the excretion of citrate. However low energy aerated drinks have not shown significant association in large cohort studies, suggesting that more than carbonated content fructose content of the drinks is the main culprit for urolithiasis [50]. A study conducted by Ferraro et al. [51] reports that beverages such as tea, coffee reduces the risk of calculi formation as studies have noticed that caffeine intake is associated with increased urinary output. Still excess consumption of tea, coffee is not advisable as it may interfere with other metabolic reactions which influence changes in the blood pressure**.** Hot beverages such as beer, alcohol have shown controversial results for their association with stone formation. In the study conducted by Ferraro et al., these drinks have shown to reduce the risk of stone formation as they reduce the activity of antidiuretic hormone and helps to excrete excess amount of diluted urine [51]. In contrast to this, a study conducted by Borghi et al. reports that alcohol intake should be avoided in case of urolithiasis patients as it will be rich in purine and it may cause hyperuricosuria [46]. Another study conducted by Rodgers et al., found that magnesium and calcium content of mineral water acts as protective in case of calcium oxalate stones [52]. Studies conducted on effect of various fruits juices have shown its impact on stone formation. Fresh lemon juice involved in the excretion of citrate and reduces excretion of calcium in urine. In concern with non-citrus fruits the results of the studies are still controversial as some fruits have shown beneficiary effect whereas some have not shown any significant association with urolithiasis [53]. Thus, these studies suggests that all fluids are not having same effect on urolithiasis. So, it's advisable to reduce the intake of sweetened beverages and high citrate content drinks as they have shown unfavourable outcomes in KSD patients.
