AQP2 and hydronephrosis: ClC-K1 and AQP-2, which mediate the transepithelial transport of chloride and water, respectively, in the renal nephrons, play a crucial role in urine concentration, and the ablation of Clck1 or Aqp2 or mutation of Aqp2 results in the rapid development of nephrogenic diabetes insipidus followed by hydronephrosis [31], [32], [33], [34].