Moderate hydronephrosis is more serious, it is recommended to actively go to the hospital to clarify the cause of moderate hydronephrosis. The most common clinical causes of hydronephrosis: 1, urinary tract infection, 2, kidney stones, 3, tumor metastasis compression. To treat fluid retention caused by urinary tract infection, it is recommended to use antibacterial drugs for two weeks. If it is caused by stones, it is recommended to actively discharge the stones, perform extracorporeal shock wave lithotripsy or insert ureteral stent and then perform surgical stone removal treatment. If it is caused by tumor compression, if there is still an indication for surgery, then surgical treatment; if there is no indication for surgery, it is recommended to actively carry out pyelostomy to relieve the symptoms of compression. If the hydronephrosis is not treated in time, it can compress the blood supply of kidney and affect the renal function. If the renal function is impaired for a long time, it can cause chronic renal failure and end-stage renal disease, which will lead to irreversible consequences.