Authors response: Ingestion of dug well water from an area with high prevalence of chronic kidney disease of unknown aetiology (CKDu) and development of kidney and liver lesions in rats-Toxicological viewpoint

Questionnaire based study was performed in two Medical Officer of Health (MOH) areas in North Central Province (NCP) namely, Dimbulagala and Medirigiriya in order to select suitable water sources. Previous investigations carried out by health authorities using dipstick method revealed that high microalbuminuria and these areas were identified as CKDu prevalent. Other causative factors such as diabetes mellitus, high blood pressure etc. were excluded in these investigations. Each MOH area comprised of Public Health Inspectors areas of New Town Medirigiriya (NTM) and Bisobandaragama (BB) from Medirigiriya and Divuldamana (DD) from Dimbulagala. People were questioned in order to identify whether they have CKDu patients in their families identified by health authorities, their regular water source, depth of their wells and number of years of consumption of water and boiled and unboiled water and nature of consumed water. One hundred and thirty nine families were recruited to the study and according to the questionnaire based study, 23 families were identified as affected and of them, 9 families were from New Town Medirigiriya and 9 families from Bisobandaragama Medirigiriya whilst 5 families were from Divuldamana, Dimbulagala [1]. Wells were selected considering number of CKDu patients in the locality or close proximity to the locality in the selected villages [2]. According to questionnaire based study there was a significant association between number of years of consumption of water and development of CKDu [2]. Water from Colombo was used as a control from a low CKDu disease prevalence area based on scientific evidence. A previous study by Gunarathne et al among 131 patients (2.5:1 male to female 2.5:1) with a mean age of 47.8±13.7 years in the National Hospital of Colombo, Sri Lanka revealed that common causes for CKD are diabetic nephropathy (n=37, 30.6%), hypertension (n=16, 13.2%), glomerular nephritis (n=12, 9.9%) and obstructive uropathy (n=10, 8.3%). The aetiology could not be identified in 25.6% of CKD patients. In this study group 50% of the patients were from the Western Province of Sri Lanka. The leading cause of CKD in patients from the Western Province of Sri Lanka was diabetic nephropathy (n=26, 37.7%). But aetiology of CKD was unknown in majority of the patients (n=14, 27.4%) from other provinces [3]. Though this difference was not statistically significant the authors hypothesized that water from Colombo was a good control to represent low endemic areas for CKDu. Not all but some suspected causative factors such as fluoride, Fe, calcium, cadmium and arsenic were analyzed in selected wells from high disease prevalent areas as well as in Colombo and summarized in the table provided with the original manuscript (Table 1, page 23).