Patients with a normal workup may still need to increase their fluid intake [5, 8, 10]. As mentioned previously, patients may behave differently on the day of their workup and may not maintain a sufficient fluid intake to prevent stones on a daily basis. Furthermore, there is evidence that patients who have a history of stone formation have a higher risk of forming stones at a given urine volume compared to individuals who do not form stones. Thus, patients with a normal workup and a propensity to form stones should still be advised to increase fluid intake. Evidence suggests that in stone formers, stone risk increases dramatically when urine volume drops below 1.6 L/day. To minimize stone risk according to the AUA guidelines , patients should drink sufficient liquid to excrete a urine volume of roughly 2.5 L/day [5]. If stones still recur at this urine volume, fluid intake may need to be increased further in order to increase urine output to 3 L/day, or even higher if stones continue to recur [8].

Individuals attempting to increase fluid consumption to diminish stone risk should also be counseled on the type of liquids that may best mitigate risk factors. Patients should focus on increasing fluid intake, while recognizing that the fluid of most beverages will lower risk more than the hypothetical increased risk of the contents of some beverages. Additionally, it may be worthwhile to counsel patients regarding the content of calcium and other minerals in the water a patient drinks. While there is insufficient evidence that individuals who drink hard water have a higher risk of stones, patients commonly ask about their water source and its potential effect. Rodgers showed that in stone formers, ingestion of a mineral water rich in calcium and magnesium showed beneficial parameters on a 24 h urine test compared to tap water [11]. Schwartz et al. reviewed 4,833 stone formers by zip code, and used the zip code to stratify patients by water hardness based on information provided by the Environmental Protection Agency. No difference on lifetime stone episodes was detected in regions with hard or soft water, although 24 h urine calcium, magnesium, and citrate levels were higher in the hard water regions [12].

Observational studies have shown a decreased risk of stone formation with increased consumption of tea, coffee, decaffeinated coffee, and alcoholic beverages [13, 14]. Curhan et al. demonstrated in a prospective trial a decreased risk of stone formation with intake of both caffeinated and decaf coffee (10%), tea (14%), beer (21%) and wine (39%). This information is important to share with patients as many practitioners incorrectly counsel that coffee and tea increase stone risk through their oxalate content. Finally, patients should be advised to avoid drinking fluids that may increase their risks of forming stones. Drinks associated with a higher risk of stones include those flavored with high sugar content. Schuster et al. showed that stone formers who simply abstained from drinking sugar sweetened soft drinks decreased their incidence of stone formation by 7% [23]. Additionally, Ferraro revealed that patients who drank one or more sugar sweetened sodas per day had a 23% increased risk of stone formation, and those who ingested one or more sugar sweetened non soda beverages had an increased risk of 33% [14].

Patients may struggle to adhere to the recommendations for increased fluid intake. Some patients may have lifestyles or professions that make high-volume liquid consumption or frequent trips to the restroom difficult [8]. Additionally, patients with colitis, Crohn’s disease , or other bowel disorders may have difficulty maintaining urine output due to gastrointestinal fluid losses, and often require input from Gastroenterology colleagues to better manage the chronic diarrhea [15].

Timing of fluid intake may help prevent stones. Although it may result in nocturia, drinking before bedtime prevents dehydration form the lack of fluid intake. Stone formers would not go 6–8 h without fluid intake in the daytime, so they need to drink enough to stay hydrated at night. Otherwise, the relative dehydration at night caused by poor fluid intake results in an increased risk of crystallization of stone forming constituents. If nocturia presents a barrier to nighttime fluid intake, patients may need further Urologic evaluation to improve this condition.

High urine oxalate is a risk factor for the formation of calcium oxalate stones [5, 8, 16]. However, dietary intake of oxalate is a controversial risk factor for stone formation. There is some evidence that dietary oxalate contributes to stone formation, however there is limited evidence that limiting dietary oxalate decreases stone risk. This is because dietary oxalate may not be bioavailable and therefore may not be readily absorbed. Oxalate that is in crystal or precipitated forms, which is what is typically found in food, is less likely to be absorbed. In patients with normal 24 h urinary oxalate levels, restriction of dietary oxalate is unlikely to significantly affect stone risk. However, if the oxalate level is borderline high and the patient persists in forming calcium oxalate stones, per the AUA guidelines, a mild oxalate restriction combined with maintaining normal calcium may help decrease the risk of future stone formation [6]. In spite of the fact that dietary oxalate may not be bioavailable, there may be other dietary sources of urine oxalate. Several oxalate precursors, including hydroxyproline and ascorbic acid, may be found in the diet and could contribute to oxalate excretion .