GDF15 and hydronephrosis: Although an apparent trend toward lower GDF-15 concentrations with increasing hydronephrosis grade was observed (Grade 0: urine 2167 pg/mL, serum 537.1 pg/mL; Grade 1: urine 1811 pg/mL, serum 468.8 pg/mL; Grade 2: urine 1637 pg/mL, serum 334.8 pg/mL), these differences were not statistically significant (p > 0.05).