The treatment of hydronephrosis often requires surgery. Decisions about diagnosis and treatment plans should be based on clinical symptoms, the duration of the obstruction, the location of the obstruction, and whether there is an infection. Since hydronephrosis is typically caused by a pathological factor that blocks the ureter, surgery is often necessary to remove the obstruction in order to address the hydronephrosis and prevent further damage to kidney function. The principle of the surgery is that if the obstruction is minor, a simple corrective surgery may suffice. However, if the dilation of the ureter and renal pelvis is very significant, a reanastomosis of the ureter and renal pelvis might be needed.