Hydronephrosis is an obstruction in the ductal part of the urinary system, resulting in dilatation of the renal pelvis and calyces, and poor urine excretion and retention in them, called hydronephrosis. Long-term hydronephrosis can bring a series of organ and even systemic damage. Specifically, the first, hydronephrosis combined with infection, because the urine can not be discharged in a timely and normal manner, easily lead to bacterial infection in the urine, can appear urinary frequency, urinary urgency and other bladder irritation symptoms, may also appear back pain, fever and other pyelonephritis manifestations, serious cases appear renal pus and systemic symptoms of infection poisoning. Second, kidney stones, long-term postoperative fluid accumulation, resulting in the formation of secondary kidney stones such as crystals in the urine, or bacteria. Stones can also aggravate the obstruction and fluid accumulation in the upper urinary tract. Third: kidney function damage, hydronephrosis will cause the pressure of the pelvis and calyces to rise, affecting the filtration of the glomerulus, and even urine reflux, damaging the kidney parenchyma, thinning the kidney parenchyma, thus affecting the function of the kidney, unilateral hydronephrosis affects the function of a single kidney, bilateral severe, continuous hydronephrosis will cause a decline in total kidney function, and even kidney failure. Therefore, it is necessary to detect and diagnose hydronephrosis in a timely manner, and to closely follow up and observe it, and to treat it in time if necessary, in order to avoid further damage to the body by hydronephrosis.