Climate change and nephrology

Abstract

Climate change should be of special concern for the nephrologist, as the kidney has a critical role in protecting the host from dehydration, but it is also a favorite target of heat stress and dehydration. Here we discuss how rising temperatures and extreme heat events may affect the kidney. The most severe presentation of heat stress is heat stroke, which can result in severe electrolyte disturbance and both acute and chronic kidney disease (CKD). However, lesser levels of heat stress also have multiple effects, including exacerbating kidney disease and precipitating cardiovascular events in subjects with established kidney disease. Heat stress can also increase the risk for kidney stones, cause multiple electrolyte abnormalities and induce both acute and chronic kidney disease. Recently there have been multiple epidemics of CKD of uncertain etiology in various regions of the world, including Mesoamerica, Sri Lanka, India and Thailand. There is increasing evidence that climate change and heat stress may play a contributory role in these conditions, although other causes, including toxins, could also be involved. As climate change worsens, the nephrologist should prepare for an increase in diseases associated with heat stress and dehydration.

Keywords: CKD of non-traditional cause; CKD of uncertain etiology; CKD of unknown etiology; Mesoamerican nephropathy; Sri Lankan nephropathy; dehydration; global warming; heat stress; heat stroke; nephrolithiasis.

FIGURE 1

Renal manifestations of heat stroke and heat-associated illness. Heat stroke refers to a condition of high body core temperatures (>40°C) associated with mental status changes and can occur from simple heat exposure (classic or epidemic form) or from the combination of heat and exercise. The second form is more commonly associated with AKI and electrolyte abnormalities. In both cases, AKI may occur from either rhabdomyolysis (rhabdo) or from direct effects of heat. Both can be associated with electrolyte abnormalities and increased risk for CKD. Less severe heat-related illnesses in which body temperature does not reach 40°C are being increasingly recognized as also increasing the risk for AKI, electrolyte abnormalities and CKD.

FIGURE 2

Pathogenesis of heat stroke. Heat stress leads to an increase in temperature. One of the basic defense systems is sweating, which can lead to dehydration and extracellular volume depletion. Increasing core temperatures also activate inflammatory pathways. The consequence is multiple organ dysfunction and increased risk for death.

FIGURE 3

Proposed pathogenesis of CKDu. Current thinking is that heat stress may lead to CKD via two major pathways. One mechanism results from excessive sweating, leading to dehydration, extracellular volume depletion and electrolyte abnormalities. The other major mechanism is from the effects of hyperthermia, stimulating inflammation, causing energy depletion and activating the sympathetic nervous system and renin–angiotensin system. RBF, renal blood flow; ADH, antidiuretic hormone or vasopressin.