An Investigation Into the Cardiovascular Risk and Aetiology of CKDu in Sri Lanka

Chronic kidney disease (CKD) is one of the leading causes of hospital admission, clinic attendance and mortality in some provinces of Sri Lanka. In central and southern provinces increased incidence is attributed to type-2 diabetes and hypertension; however, this is not the case in North Central Province (NCP) where CKD of unknown aetiology (CKDu) is the commonest diagnosis. A recent World Health Organisation (WHO) investigation concluded that at least 8,000 people have CKDu2. First recognized in the early nineties, much work has been done to try to characterise the disease however results are conflicting. Most suggest male paddy farmers working in rural areas of the NCP are worst affected, presenting in their fifth decade with end stage renal failure. However, a recent WHO study revealed higher prevalence in females, although more severe renal impairment was more common in men. Risk factors include inhabiting NCP \> five years, inhabiting the 'dry zone', reduced BMI, lower socio-economic class, and exposure to agrochemicals. There has been suggestion of a genetic link although positive family history is limited to one generation, with no evidence of mendelian progression. Epidemiological studies reveal a clustered geographical distribution with areas such as Medawachchiya, Padaviya and Girandurukotte most affected. High prevalence areas encompass a well-developed irrigation system used for agricultural purposes. Renal biopsies show tubulointerstitial disease with tubular atrophy, interstitial mononuclear cell infiltration, interstitial fibrosis but no immune-complex deposition on immunofluorescence. This supports a toxin-mediated process. Many aetiologies have been considered including exposure to heavy metals (cadmium, arsenic) and their chelation by herbicides, fluro-aluminium complexes, agricultural pesticides, mycotoxins, and herbal medicines. Selenium deficiency and genetic susceptibility may be predisposing factors. The true aetiology is likely multifactorial. The multi-system impact of CKDu has yet to be fully realised. Epidemiological and clinical data show that damage to large arteries contributes to the increased cardiovascular risk observed in CKD. Atherosclerosis is the most frequent cause of arterial damage but the medial calcification seen in CKD also leads to arterial stiffening. This stiffening causes elevation in systolic blood pressure, increasing left ventricular workload with the gradual development of LVH, and also a fall in diastolic blood pressure impairing coronary blood flow. Arterial calcification and stiffness are independent predictors of all-cause and cardiovascular mortality in patients with CKD. Arterial stiffness will be compared in CKDu patients, healthy Sri Lankan controls and CKD patients both in Sri Lanka and Scotland. We will perform a prospective observational study of up to 250 patients with CKDu presenting to renal clinics in Teaching Hospital, Anuradhapura. Patient history, basic anthropometric measurements, and simple non-invasive tests (e.g. blood pressure and arterial stiffness) will be performed. Urine, serum and plasma samples will be collected for quantitative PCR, and further analysis for biomarkers of renal injury, exosomes, proteomics and any DNA-adducts. Patients will be graded using the WHO CKDu grading system. When a renal biopsy is performed, a copy of the light microscopy findings will be obtained. Comparisons of interest will be tested via paired t-tests with statistical significance taken at 5%.