Case series / case reportindependent cross-checkabstract checked I-VEG-121 standard review
Mayo Clinic: diet behind some oxalate kidney damage
Clinical Outcomes and Histological Patterns in Oxalate Nephropathy due to Enteric and Nonenteric Risk Factors.
Overview
Reddy S et al.. Am J Nephrol 2021 · PMID 34844241 · DOI 10.1159/000520286
Of 64 biopsy cases, 7 were attributed to dietary oxalate; outcomes were often poor.
Does the study support the specific claim? Yes · Methodological quality: low
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Characterise non-primary oxalate nephropathy.
- How was the study done?
Retrospective biopsy cohort.
- How many people, animals or samples were studied?
64 patients.
- What was actually found?
Diet one cause among several; severe outcomes.
- How large was the observed effect?
7/64 dietary.
- What do the results mean in everyday life?
Extreme oxalate diets can damage kidneys, but this is rare.
- What are the study's limitations?
Selected cases.
- What does it say about Elawady's specific claim?
Supports conditional claim.
- Do the results apply to Germany and Europe?
Universal.
- What can explicitly not be concluded from this study?
Cannot estimate risk for juicers.
Scientific in-depth review
1. Full reference
- Authors
- Reddy S et al.
- Journal
- Am J Nephrol
- Year
- 2021
- Identifier
- PMID 34844241 DOI 10.1159/000520286
- Verification
- verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
What are the risk factors, histology and outcomes of oxalate nephropathy not due to primary hyperoxaluria?
3. Study design and population
- Study design
- Case series / case report – Retrospective biopsy cohort (Mayo Clinic pathology repository)
- Population
Native-kidney biopsies with oxalate nephropathy, Mayo Clinic sites
- Country
USA
- Period
2009-2020
- Sample size
421 ON cases screened; 64 analysed
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
Enteric vs non-enteric risk factors (incl. dietary oxalate, vitamin C)
- Comparator
Enteric vs non-enteric
- Endpoints
Dialysis, transplant, death
- Statistical methods
Univariate and multivariate analysis
5. Actual results
- Results
Enteric risk factors in 30, non-enteric in 34; among non-enteric: vitamin C 7, dietary oxalate 7, no apparent risk 16. AKI stage III in 60%; 40.6% required dialysis; after median 10 months 39% dialysis-dependent, 11% transplanted, 32% died.
- Absolute risks
not reported
- Authors' conclusion
Histologic features differ by risk group; AKI requiring dialysis was the main predictor of adverse outcome.
6. Strengths
- Largest single-centre cohort of non-primary ON
7. Weaknesses
- Retrospective; referral population; no denominator of exposure
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- high
- Rationale
Retrospective case series.
9. Assessment of the statistical interpretation
Dietary oxalate 7/64 = 11% (stats/C-VEG-06_oxalate_nephropathy.py).
10. Relevance to the specific claim
Confirms that dietary oxalate is a recognised but uncommon cause of biopsy-proven oxalate nephropathy.
11. Independent contrary findings
none
12. Transferability to Germany and Europe
Universal.
13. Overall methodological judgement
Supports the claim as a rare event.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | low |
| Risk of bias | high |
| Precision of results | not applicable |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Incidence.