During mountain running events, athletes can experience muscular impairment as well as adverse health conditions of cardiovascular, immunological, renal and hepatic nature. Specifically, regarding the renal system, it has been shown that physical stress is a factor that contributes to the transitory decrease of renal function known as acute kidney injury (AKI) and muscle disintegration called exertional rhabdomyolysis (ER). The aim of this study was to assess hydration status, kidney function and muscle damage during an endurance mountain running (35.3km trail run, total positive ascend 1815m). A total of 26 experienced and trained mountain runners (age 39.5 ± 9.23 years, weight 71.26 ± 11.17 kg, height 171.65 ± 8.69 cm) took part of the study. Assessments included urine specific gravity (USG), body weight (BW), creatinine (Cr), blood ureic nitrogen (BUN), albumin (ALB), glomerular filtration rate (eGFR) and creatine kinase (CK), at three distinct moments (pre, post_0h and post_24h). A repeated measures analysis of variance (ANOVA) was used to verify possible differences between measurement times. There were no differences in USG (F_(2,34)= 0.817, p= 0.45, ω_p²= 0.01), however differences were noted in BW (F_(1,26)= 5.37, p= 0.029, ω_p²= 0.16, pre>post_0h), Cr (F_(2,42)= 34.453, p< 0.01, ω_p²= 0.6, pre < post_24h <post_0h), BUN (F_(2,42)= 15.694, p< 0.01, ω_p²= 0.39, pre <post_0h< post_24h), ALB (F_(1,26)= 7.806, p< 0.01, ω_p²= 0.2, pre < post_24h <post_0h), eGFR (F_(1,26)= 5.403, p< 0.01, ω_p²= 0.15, post_0h < post_24h <pre) and CK (F_(1,26)= 18.957, p< 0.01, ω_p²= 0.43, pre < post_24h <post_0h). Along with a decrease in body weight (BW loss >2%), a decrease in eGFR and a rise in ALB, BUN, CK and AKI was found (acute absolute Cr difference >0.3 mg/dL). This constellation of values supports the idea that endurance mountain running can lead to AKI and muscle injury because of mechanical damage of both kidney and muscle due to repeated effort.