Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka

Chronic kidney disease of unknown aetiology (CKDu), which is widespread in the North Central Province (NCP) of Sri Lanka, is not associated with commonly known factors such as diabetes, hypertension, and glomerulonephritis. The pathogenicity of CKDu is not well understood, but people with a low body mass index (BMI) and mineral and nutrient deficiencies are more vulnerable to develop CKDu. To understand this situation, the relationship between BMI and the estimated glomerular filtration rate (eGFR) was investigated in people with CKDu in comparison with unaffected age-matched control groups in disease-endemic areas of the NCP. This community-based cross-sectional study was performed in Medirigiriya in the Polonnaruwa district of Sri Lanka, which has one of the highest densities of patients with CKDu. The data for identifying demographic factors and the relationship between CKDu and BMI were investigated by using a validated survey questionnaire. Findings indicated that the group with the highest number of people affected with CKDu (i.e. eGFR of less than 60 mL/min/1.73 m²) had the lowest BMI compared to those with normal eGFR. The majority affected were male farmers. The severity of the disease was inversely associated with BMI values and had a higher prevalence of smoking and alcohol consumption. In addition, those who consume water from household dug wells had significantly lower eGFR (p < 0.0001). A linear regression analysis revealed a significant positive association between lower eGFR and lower BMI (p < 0.001). We hypothesised that the low BMI in those with CKDu may have increased susceptibility to develop CKDu, in the presence of exposure to multiple nephrotoxins and adverse conditions.

Chronic kidney disease of unknown aetiology in Sri Lanka and the exposure to environmental chemicals: a review of literature

Chronic kidney disease of unknown aetiology (CKDu) has emerged as a serious health issue in Sri Lanka. The disease has been recorded in the North Central Province of the country. While studies have elicited many hypotheses concerning the pathogenicity of CKDu, none adequately explains the cause of CKDu and the measures needed to minimise its occurrence. Nephrotoxic heavy metal (oid)s such as cadmium, arsenic, lead, and chromium are present in biological samples of people from endemic areas. This review appraises evidence on the effects of long-term exposure to low concentration of nephrotoxic heavy metals, which could be the principal cause of CKDu. Although a considerable variation exists in metal concentrations in patients' blood and urine, higher levels of heavy metals were consistently observed in affected areas. This review finds that the populations in the endemic areas are exposed to heavy metal (oid)s at low concentrations, which are considered as safe levels; nevertheless, it influences the incidence of CKDu. Recent global studies on chronic kidney disease (CKD) revealed a low concentration of heavy metals in diseased patients. Research findings indicated that CKDu patients in Sri Lanka demonstrated similar blood levels of Cd, Pb, and higher concentrations of Cr than that have been reported globally. Further studies on the influence of combinations of nephrotoxic heavy metals at low concentrations on reduced glomerular filtration rate and other renal biomarkers could explain CKDu pathogenicity.