Abstract

In the last twenty years, tropical Pacific lowlands of Central America have seen a dramatic increase of a rapidly progressive chronic kidney disease of unknown aetiology (CKDu), the Mesoamerican nephropathy (MeN). MeN is unexplained by conventional CKD risk factors.

An international expert workshop held in November 2015 in Costa Rica reached consensus that MeN has a major occupational component with growing evidence for a causal role of strenuous work, heat and insufficient rehydration. Other factors may also play a role, among which agrochemicals is possibly most notable. CKDu occurs in particular among sugarcane cutters, but also among workers in other hot occupations such as construction and mining, whereas it is mostly absent in occupations with less physical effort or in cooler environments. In community-based prevalence studies in Nicaragua and El Salvador, 18–42% of adult males in lowland sugarcane areas had eGFR < 60 ml/min/1.73m². In Salvadorian cane cutters cross-shift changes in serum (increases in SCr, eGFR, BUN, uric acid; decreases in chloride, potassium) and urinary markers (USG and osmolarity increased, pH decreased) were consistent with dehydration. In Nicaraguan cutters, average adverse cross-shift changes in eGFR on harvest days 1 and 6 correlated with observed eGFR loss of 10 ml/min/1.73m² over a 9-week period (corr.coeff. 0.42, p = 0.06). Another cohort of Nicaraguan cutters showed a protective effect from consumption of electrolyte solution regarding loss of kidney function over the harvest season. Animal experiments show a pathophysiological pathway from dehydration to tubulointerstitial CKD - other pathways include uric acid chrystalluria. Comparable findings have emerged from workforce assessments in the ongoing WE intervention study evaluating water, rest and shade in cutters.

Similar CKDu epidemics are occurring in tropical agricultural populations in Sri Lanka and India, and possibly in other countries, but it is unclear if the same risk factors play a role.