Mechanism of acute kidney injury in mild to moderate heat-related illness

Abstract

Abstract Background: Heat-related illnesses cause kidney injury, and recurrent minor kidney injuries may accumulate, resulting in the development of chronic kidney disease. Despite the increased incidence, the factors responsible for kidney injury in heat-related illnesses remain unclear. Our study focuses on mild-to-moderate severity cases to examine the triggers initiating kidney injury. Methods: Patients aged 18 years or older with suspected heat-related illnesses at the Juntendo University Hospital Emergency and Primary Care Center between July and September 2020 and June and August 2022 were included. Blood samples were obtained during their visit, and the patients were categorized into two groups based on their cystatin-based estimated GFR (eGFRcys) values: a kidney injury group (eGFRcys < 60 mL/min/1.73 m2) and a non-kidney injury group (eGFRcys ≥ 60 mL/min/1.73 m2). Inflammation, coagulation, and skeletal muscle damage markers were compared between the groups, and markers related to the early development of kidney injury were examined. Results: A total of 35 patients were diagnosed with heat-related illnesses, and 10 were diagnosed with kidney injury. White blood cell count was higher in the kidney injury group (P < 0.01), whereas the levels of CRP and Interleukin-6 showed no significant difference between the groups. No statistically significant differences in coagulation markers were observed. In contrast, myoglobin, a marker of skeletal muscle damage, showed elevated levels in the kidney injury group (P < 0.01) and demonstrated a stronger association with early kidney injury than creatine kinase (P < 0.05). Conclusion: The predominant mechanism of acute kidney injury in mild to moderate heat-related illnesses appears to be tubular damage caused by myoglobin. Measuring myoglobin levels is essential to identify and exclude patients at risk of acute kidney injury due to heat-related illnesses.