Kidney disease
What is causing a mysterious kidney disease in rural Sri Lanka?
Open access · cc by · source: Europe PMC
Chronic kidney disease of unknown cause was far more common in endemic Sri Lankan districts than earlier estimates suggested, and patients had higher urinary cadmium that rose with disease stage.
Study at a glance
- Design
- Cross-sectional — Random household prevalence survey in endemic districts plus comparison of urine, blood, hair and nail toxicant levels in CKDu cases versus endemic and non-endemic controls, alongside environmental sampling (2010-2012)
- N
- 6698 people aged 15-70 invited to the prevalence survey (74% responded); 733 CKDu cases identified; metal analyses on subsets (e.g. urine metals in 495 cases, 250 non-endemic controls; hair/nails in 80 cases vs 48 controls; pesticides in 57 cases vs 39 controls)
- Population
- Adults aged 15-70 without diagnosed diabetes in three endemic districts of Sri Lanka's farming regions, plus controls from a non-endemic district (Hambantota)
- Outcome
- Age-standardised CKDu prevalence; risk factors; concentrations of cadmium, arsenic, lead, selenium and pesticide residues in biological and environmental samples
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Age-standardised prevalence was 16.9% in women and 12.9% in men, much higher than earlier estimates of 2-3%, though men more often had advanced stages. Urinary cadmium was significantly higher in cases than controls from both areas and showed a dose-response with disease stage, while urinary arsenic and lead did not differ. Drinking water was mostly within safe limits, but some foods such as lotus root, plus fertilizer, had high cadmium, and many cases had low selenium and detectable pesticide residues.
Methodology
Researchers randomly sampled households in three endemic districts and invited 6698 people aged 15-70 without diabetes to be screened with repeated urine albumin tests, blood pressure and HbA1c, using a strict case definition that excluded other known kidney causes. In subsets of cases and controls (from both the endemic area and a non-endemic district), they measured arsenic, cadmium, lead, selenium and other elements in urine, blood, hair and nails, and pesticide residues in urine. They also tested water, food, soil, fertilizer and tobacco for heavy metals.
Limitations
This is cross-sectional, so higher cadmium in patients could partly reflect reduced kidney function or shared exposures rather than cause, and the modest ROC performance (AUC about 0.68) means cadmium poorly separates cases from controls. The case definition relied on albuminuria, was not validated against kidney biopsy, excluded low-GFR cases without albuminuria, and used an eGFR equation not validated in South Asians; stage 1 may inflate prevalence. Toxicant subsets were small and not all compared with the same control groups, and infections and genetics were not examined in depth.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Cadmium is a plausible kidney toxicant, but it predicts individual cases poorly.
Cadmium exposure is associated with kidney damage in two very different populations: in US NHANES adults, blood cadmium above 1 mcg/L went with higher odds of CKD (OR 1.48) and albuminuria (OR 1.41); in endemic Sri Lankan districts, urinary cadmium was higher in CKD of uncertain cause than in controls and rose with disease stage.
Evidence for the claim as stated.
Cadmium is a plausible kidney toxicant, but it predicts individual cases poorly.
Cadmium exposure is associated with kidney damage in two very different populations: in US NHANES adults, blood cadmium above 1 mcg/L went with higher odds of CKD (OR 1.48) and albuminuria (OR 1.41); in endemic Sri Lankan districts, urinary cadmium was higher in CKD of uncertain cause than in controls and rose with disease stage.
Scope note — Cross-sectional; reduced kidney function could alter cadmium handling; AUC about 0.68.
Limits the claim's scope: a different population, assay, or outcome.
Urinary cadmium behaves differently across settings: in NHANES it was linked to albuminuria but not to low-eGFR CKD (OR 0.70, not significant), while in Sri Lanka it rose with CKD stage. The populations, exposure levels and case definitions (eGFR-based versus albuminuria-based, with an eGFR equation not validated in South Asians) differ, so this is a difference of scope rather than a direct conflict.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Urinary cadmium behaves differently across settings: in NHANES it was linked to albuminuria but not to low-eGFR CKD (OR 0.70, not significant), while in Sri Lanka it rose with CKD stage. The populations, exposure levels and case definitions (eGFR-based versus albuminuria-based, with an eGFR equation not validated in South Asians) differ, so this is a difference of scope rather than a direct conflict.
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