What does post-exercise proteinuria tell us about kidneys?

Objectives. Post exercise proteinuria (PEP) is found in about 20–40% of sportsmen after intensive exercise. Urinary NGAL is a new marker of tubulointerstitial kidney damage. The relationship between PEP and uNGAL has not been defined yet. In presented study a resting uNGAL as a predictor of PEP was analyzed. The changes of albuminuria after exercise were monitored to estimate a frequency and range of PEP. Methods. 40 amateur healthy runners (mean age 36.65 ±10.61 years) participating in 10-km run took part in the study. Before and after the competition urine was collected. NGAL, albumin and creatinine were subsequently measured in urine. uNGAL to creatinine ratio (NCR) and albumin to creatinine ratio (ACR) were calculated. Results. 28 participants (mean age 37.9 ±11.46, 19 M, 9 F) with uNGAL below 15 ng/ml before competition were analyzed. The increase of ACR was observed in every case. Mean post-exercise ACR was 104.55 ±123.1 mg/g and was significantly higher than pre-exercise ACR 6.33 ±5.86 mg/g (p < 0.0005). The positive correlation was found between resting NCR and post-exercise ACR (r = 0.60, p < 0.05). Conclusions. Resting uNGAL positively correlated with PEP. The possible explanation of these findings is that persons with PEP had some early, occult tubulointersitial kidney damage. It is speculated that those runners have higher risk of chronic kidney disease.