GFR is the glomerular filtration rate, which is generally used clinically to understand renal function. The glomerular filtration rate usually recovers after drainage of hydronephrosis, but when hydronephrosis is combined with complications such as chronic renal impairment, the glomerular filtration rate usually does not recover even if the hydronephrosis is drained. Hydronephrosis refers to the obstruction of urine drainage from the renal pelvis, resulting in increased intrarenal pressure, which leads to renal hypoplasia, and accordingly, a decrease in glomerular filtration rate may occur. Generally, when the cause of obstruction is removed from hydronephrosis without complications, renal function will slowly return to normal, and glomerular filtration rate will also recover. When there is chronic renal impairment, the renal function is severely lost, and the damage is generally irreversible, even if the fluid is discharged, the glomerular filtration rate can not be restored. Patients with hydronephrosis are advised to consult regular hospitals and receive standardized treatment under the guidance of physicians.