The main goal pursued in determining the daily amount of liquid intake is to prevent the super saturation of stone forming metabolites in the urine [3]. At least 2.5 L of daily liquid intake is advised to adults to produce at least 2 L of urine [2]. Same rates should be proportioned according to the body surface area for children and the daily liquid intake should be regulated to obtain daily urine production with a rate of 2 L/1.73 m². As the urine concentration increases at nights especially in cases with cystinuria, children should be encouraged to drink water right before going to bed and when they wake up at night to urinate [6]. In case of increased fluid loss as a result of temperature rise, excessive perspiration and diarrhea, the liquid intake should be increased accordingly. Although all kinds of liquids prevent the super saturation of the urine in theory; children should avoid fruit juices, tea, coffee and cocoa drinks for their oxalate contents; tomato juice for its salt content and instant drinks sweetened with fructose associated with hyperuricuria. One of the rare fruit juices that can be recommended for children with urolithiasis is lemonade, as it increases the amount of citrate in the urine. Since instant lemonades contain fructose and a low volume of lemon juice, homemade lemonades should be preferred. Nevertheless, grapefruit, orange and apple juices are not recommended as they might increase the concentration of oxalate in the urine [7].

Patients with stone disease used to be advised to have calcium-poor diets in the past. Studies made with a large number of patients revealed an inverse proportion between the calcium oxalate stones and the amount of calcium in the diet [4]. As calcium in the bowels binds oxalate, increased amount of calcium in the diet reduces the absorption of oxalate in the bowels. In patients with fat malabsorption calcium in the diet combines with fatty acids requiring a higher amount of calcium intake than the daily recommended dose. When calcium intake in the diet is insufficient, it should be supported with calcium containing preparations. Calcium citrate is the ideal choice for this purpose, as it increases the amount of citrate in the urine at the same time.