Acute kidney injury induced by exertional rhabdomyolysis in military personnel

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BACKGROUND: Exertional rhabdomyolysis is a relatively common condition among military personnel and athletes, potentially leading to acute kidney injury. This study describes the occurrence of exertional rhabdomyolysis and pre-renal or intrinsic acute kidney injury in elite military personnel undergoing intense operational training, emphasizing readily accessible serum and urinary biochemical markers that may serve as early warning signs. METHODS: The study included 19 recruits from the Brazilian Marine Corps who completed the Amphibious Command Course, involving rigorous training and dietary restrictions in a tropical mountainous region, from an initial group of 60 highly trained personnel. Exertional rhabdomyolysis was evaluated through serum creatine kinase, myoglobin, and lactate dehydrogenase. Kidney function was assessed using serum creatinine, urea and phosphate. Acute kidney injury was defined according to Acute Kidney Injury Network criteria. The diagnosis of pre-renal or intrinsic acute kidney injury was based on urinary sodium/potassium (uNa/uK) ratio, uK/(uK + uNa) ratio, fractional excretion of sodium, and fractional excretion of urea. RESULTS: Post-training analyses showed significant increases in biomarkers of muscle and kidney damage. All participants developed exertional rhabdomyolysis, and nine presented with acute kidney injury, all of which were classified as pre-renal. In detail, serum CK, LDH, myoglobin, and AST significantly increased after physical exertion. CK levels then declined by the end of the mission and returned close to baseline after seven days. CONCLUSION: This exploratory study indicates a high frequency of exertional rhabdomyolysis and pre-renal acute kidney injury in this specific cohort of elite military personnel undergoing intense physical training. Given the limited sample size (n = 19), the findings should be considered preliminary. The identified biomarkers may assist in monitoring kidney function and muscle injury but require validation in larger and more diverse cohorts before broad clinical application.