Systematic reviewindependent cross-checkabstract checked★ key study I-FAST-122 in-depth review
Drinking more water to prevent kidney stones
Water for preventing urinary stones.
Overview
Bao Y et al.. Cochrane Database Syst Rev 2020 · PMID 32045491 · DOI 10.1002/14651858.CD004292.pub4
People who had kidney stones and drank enough to pass 2 litres of urine a day had fewer new stones.
Does the study support the specific claim? No · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Assess water for stone prevention.
- How was the study done?
Cochrane review.
- How many people, animals or samples were studied?
1 RCT, 220 people.
- What was actually found?
RR 0.45 for recurrence.
- How large was the observed effect?
149 fewer recurrences per 1000.
- What do the results mean in everyday life?
Stone formers should drink more than thirst alone suggests.
- What are the study's limitations?
Only one trial.
- What does it say about Elawady's specific claim?
Limits the thirst-only rule; contradicts water restriction.
- Do the results apply to Germany and Europe?
Applicable; stone disease common in Egypt's hot climate.
- What can explicitly not be concluded from this study?
Primary prevention.
Scientific in-depth review
1. Full reference
- Authors
- Bao Y et al.
- Journal
- Cochrane Database Syst Rev
- Year
- 2020
- Identifier
- PMID 32045491 DOI 10.1002/14651858.CD004292.pub4
- Verification
- verified – PubMed efetch 2026-10-26; Crossref update-to/updated-by check
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
None known.
2. Research question
Does increased water intake prevent urinary stones?
3. Study design and population
- Study design
- Systematic review – Cochrane systematic review of RCTs
- Population
People with or without history of stones
- Country
Italy (the single included RCT)
- Period
Search to 15 Oct 2019
- Sample size
1 RCT, 220 randomised (199 analysed)
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
Increased water intake to urine volume >=2.0 L/day
- Comparator
Standard water intake
- Endpoints
Stone recurrence, time to recurrence, adverse events
- Statistical methods
RR, HR; GRADE
5. Actual results
- Results
No RCT for primary prevention. Secondary prevention: recurrence RR 0.45 (95% CI 0.24-0.84; low certainty), 149 fewer per 1000 over 5 years (control 270/1000); time to recurrence HR 0.40 (0.20-0.79). No evidence on adverse events.
- Absolute risks
270 vs about 122 recurrences per 1000 over 5 years (ARR about 15%, NNT about 7; stats/I-FAST-122_water_stones.py).
- Authors' conclusion
Increased water intake achieving >=2.0 L urine/day may reduce stone recurrence; confidence limited; no RCT evidence for primary prevention.
6. Strengths
- Cochrane methods
- Absolute effects reported
7. Weaknesses
- Single trial (same as I-FAST-09)
- Low certainty
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Review well conducted; evidence base is one trial.
9. Assessment of the statistical interpretation
Same data as Borghi 1996; not an independent confirmation.
10. Relevance to the specific claim
Shows that for stone formers, drinking deliberately more than thirst dictates helps; limits 'drink only when thirsty' and contradicts 'do not drink much water'.
11. Independent contrary findings
12. Transferability to Germany and Europe
Universal biology; applies in Europe and Egypt.
13. Overall methodological judgement
Low-certainty but relevant evidence for a common condition in hot climates.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | low |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | unknown |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Drink water only when thirsty; there is no need to force a fixed daily amount. – Studies contradicting or limiting the claim
- Do not drink much water because it distends the abdomen and raises abdominal pressure; even when thirsty during long fasting hours just wet the lips; fasting three days in a row each week without food and drink is not harsh. – Studies contradicting or limiting the claim