Prevalence and risk factors of chronic kidney disease of unknown etiology in Northeast Thailand.

Background: Chronic kidney disease of unknown etiology (CKDu) has been reported mainly in agricultural communities, in hot and humid climates, but whether this is occurring in Thailand has not been fully documented. The prevalence of CKD is higher in Northeast Thailand compared to other parts of the country and this region is hot, tropical, and agriculturally based. Therefore, we evaluated the prevalence of CKDu determined by various criteria and the associated risk factors of CKDu in this region.

Methods: A population-based survey was conducted in rural sub-districts between 2017-2019 in which blood and urine samples were collected for determination of CKD, and ultrasonography was performed to evaluate for renal structural abnormalities. Public and household water were analyzed for contaminants: sixteen samples of water within the study area, encompassing natural untreated surface water sources, shallow groundwater, and locally produced tap water were collected for physical and chemical analyses based on the guidelines for drinking-water quality, as recommended by the World Health Organization (WHO) in 2011. The mandatory criteria were: suspected CKDu one time measurement CKDu1: eGFR < 60 mL/min, CKDu2: eGFR < 60 mL/min and dipstick protein ≤ 1 +, in the absence of evidence of other kidney diseases or diabetes. Further assessment included: Repeat assessment after 12 weeks, confirmed one or more of; - eGFR < 60 ml/min/1.73 m², Albuminuria ≥ 30 mg/g Cr, Hematuria > 3 RBCs/high power field. Ultrasound criteria were confirmed parenchymatous change without other structural abnormalities, assessed by two radiologists.

Results: The prevalence of CKD was 26.85% in the study population (n = 2205) including 6.26% of unknown etiology. The percentages of probable or possible CKDu in participants aged ≤ 70 years as assessed by different criteria were 5.48% (this study criterion); 4.27% (Sri Lanka 2018 criterion); 2.53% (India 2017 criterion) and 1.48% (Mesoamerican 2020 criterion). CKDu was significantly associated with age, male sex, increase in serum uric acid and leukocyte count, decrease in hemoglobin, and consumption of groundwater contaminated with potential nephrotoxins (such as cadmium, lead, fluoride, and glyphosate). The analysis of the 16 water samples revealed that 14 (from natural surface water, shallow groundwater and locally produced tap water) contained heavy metals exceeding the standard limits.

Conclusions: CKDu is present in rural northeastern Thailand. The observation of a link with groundwater contaminated with cadmium, lead, fluoride and glyphosate should be further investigated.