Hydrotherapy for Kidney Stones
Increased fluid intake (hydrotherapy) is highly effective for preventing kidney stone recurrence and should be the first-line treatment for all patients with nephrolithiasis, targeting at least 2 liters of urine output per day. 1, 2
Evidence for Effectiveness
The American College of Physicians establishes increased fluid intake as the foundational intervention before any pharmacologic therapy is considered. 3 The evidence demonstrates substantial benefit:
Patients who increase fluid intake to achieve >2L urine output daily reduce stone recurrence from 27.0% to 12.1% over 5 years (a 55% relative risk reduction). 3, 4
Meta-analysis of randomized controlled trials shows a pooled risk ratio of 0.40 (95% CI 0.20-0.79), meaning 60% reduction in recurrent kidney stones with high fluid intake. 4
Observational studies confirm similar benefit with risk ratio of 0.49 (95% CI 0.34-0.71) for incident stones and 0.20 (95% CI 0.09-0.44) for recurrent stones. 4
Practical Implementation
Target urine output of at least 2 liters per 24 hours, which typically requires drinking 2.5-3 liters of fluid daily depending on climate and activity level. 1, 5, 2
Type of Water
Regular tap water is equally effective as mineral water for stone prevention—no need to purchase expensive mineral waters. 3, 2
One study showed oligomineral water (Fiuggi brand with 15 mg calcium/L) had marginally better outcomes than tap water (17.0% vs 22.9% recurrence), but this difference was not clinically significant and other mineral waters have not been studied. 3
Beverages to Avoid
Eliminate colas and soft drinks acidified with phosphoric acid, which increase stone risk (45.6% recurrence with phosphoric acid sodas vs 29.7% without). 3, 1
Fruit-flavored sodas acidified with citric acid do not show the same harmful effect. 3
When Hydrotherapy Alone Is Insufficient
If increased fluid intake fails to prevent stone recurrence after adequate trial (typically 6-12 months), pharmacologic monotherapy should be added based on metabolic profile:
Thiazide diuretics for hypercalciuria (reduces recurrence from 48.5% to 24.9%). 1
Potassium citrate for hypocitraturia (reduces recurrence from 52.3% to 11.1%). 1
Allopurinol for hyperuricosuria with normal urinary calcium (reduces recurrence from 55.4% to 33.3%). 1
Monitoring Response
Obtain 24-hour urine collection at 6 months after initiating increased fluid intake to verify adequate urine volume (>2L/day) and assess other metabolic parameters (calcium, oxalate, uric acid, citrate, sodium). 1, 5
Safety Considerations
High fluid intake appears safe with no withdrawals due to adverse events reported in trials. 4 However, exercise caution in patients with:
- Heart failure or volume overload states
- Hyponatremia or conditions predisposing to hyponatremia
- Advanced chronic kidney disease with impaired free water excretion
These patients were typically excluded from clinical trials. 4
Critical Pitfalls
Do not advise calcium restriction—this paradoxically increases urinary oxalate and stone risk. Instead, maintain normal dietary calcium intake of 1,000-1,200 mg/day. 1, 6
Do not rely on patient self-report of fluid intake—verify with 24-hour urine volume measurement, as patients frequently overestimate their intake. 7
Do not delay fluid intake counseling—this should begin immediately at diagnosis, not after metabolic workup is complete. 1, 2